Showing papers on "Seedling published in 1968"

The ecology of arctic and alpine plants

Abstract: Summary ‘How are plants adapted to the low temperatures and other stresses of arctic and alpine environments ?’ At present it is not possible to answer this question completely. Much work remains to be done, particularly on low-temperature metabolism, frost resistance, and the environmental cues and requirements for flowering, dormancy, regrowth, and germination. However, in brief, we can say that plants are adapted to these severe environments by employing combinations of the following general characteristics: 1. Life form: perennial herb, prostrate shrub, or lichen. Perennial herbs have greatest part of biomass underground. 2. Seed dormancy: generally controlled by environment; seeds can remain dormant for long periods of time at low temperatures since they require temperatures well above freezing for germination. 3. Seedling establishment: rare and very slow; it is often several years before a seedling is safely established. 4. Chlorophyll content: in both alpine and arctic ecosystems not greatly different on a land-area basis from that in temperate herbaceous communities. Within a single species there is more chlorophyll in leaves of arctic populations than in those of alpine populations. 5. Photosynthesis and respiration: (a) These are at high rates for only a few weeks when temperatures and light are favourable. (b) Optimum photosynthesis rates are at lower temperatures than for ordinary plants; rates are both genetically and environmentally controlled with phenotypic plasticity very marked. (c) Dark respiration is higher at all temperatures than for ordinary plants; rate is both genetically and environmentally controlled, with phenotypic plasticity very pronounced, i.e. low-temperature environment increases the rate at all temperatures. (d) Alpine plants have higher light-saturation values in photosynthesis than do arctic or lowland plants; light saturation closely tied to temperature. (e) There is some evidence that alpine plants can carry on photosynthesis at lower carbon dioxide concentrations than can other plants. (f) Annual productivity is low, but daily productivity during growing season can be as high as that of most temperate herbaceous vegetation. Productivity can be increased by temperature, nutrients, or water. 6. Drought resistance: most drought stress in winter in exposed sites is due to frozen soils and dry winds. It is met by decreased water potentials, higher concentrations of soluble carbohydrates, and closed stomates. Little drought resistance in snowbank plants. Alpine plants adapted to summer drought stress can carry on photosynthesis at low water potentials; alpine or arctic plants of moist sites cannot do this. 7. Breaking of dormancy: controlled by mean temperatures near or above 0° C., and in some cases by photoperiod also. 8. Growth: very rapid even at low positive temperatures. Respiration greatly exceeds photosynthesis in early re-growth of perennials. Internal photosynthesis may occur in hollow stems of larger plants during early growth. Nitrogen and phosphorus often limiting in cold soil. 9. Food storage: characteristic of all alpine and arctic plants except annuals. Carbohydrates mostly stored underground in herbaceous perennials. Lipids in old leaves and stems of prostrate evergreen shrubs. Depleted in early growth, and usually restored after flowering. 10. Winter survival: survival and frost resistance are excellent after hardening. Cold resistance closely tied to content of soluble carbohydrates, particularly raffinose. 11. Flowering: flower buds are pre-formed the year before. Complete development and anthesis dependent upon temperature of the flowering year and also, in some cases, upon photoperiod. 12. Pollination: mostly insect-pollinated in alpine regions and even in Arctic, but to a lesser extent. Wind-pollination increasingly more important with increasing latitude. Diptera more important than bees in the Arctic and in the highest mountains. 13. Seed production: opportunistic, and dependent upon temperature during flowering period and latter half of growing season. 14. Vegetative reproduction: by rhizomes, bulbils, or layering. More common and important in Arctic than in alpine areas. 15. Onset of dormancy: triggered by photoperiod, low temperatures, and drought. Dormant plant extremely resistant to low temperatures.

Autotoxic Feedback in Relatin to Germination and Seedling Growth in Typha Latifolia

Abstract: Seed germination of Typha latifolia was completely inhibited by an aqueous extract of cattail leaves but was only partially inhibited by extract treated with polyclar AT to remove phenolic compounds. Seedling growth was slightly inhibited by water from cattail marshes, was highly inhibited by water squeezed from soil in which cattails were growing, and was stimulated (as compared with the distilled water control) by water obtained from a Sphagnum bog. Cattail populations, once established, may this effectively preclude invasion by alien typha genotypes, and the autotoxic properties of the accumulated organic residues may accentuate the unidirectional orientation of marsh succession. See full-text article at JSTOR

Ecological aspects of seed health testing

Abstract: The purpose of this study was to investigate the factors affecting the outcome of incubation methods used to test seeds for the presence of fungal pathogens The reason for starting such an investigation was the poor reproducibility of the results of those methods Chapter 3 starts with the observation that for a number of infections lower percentages are found on blotters with a relatively high moisture content than on blotters with a lower moisture content This so-called 'wet blotter effect' (WBE) was found to be related to the speed of water uptake by the seeds; if the water uptake is relatively slow the effect does not show, whereas in the case of more rapid water absorption the effect can be noted If the rate of water uptake of seeds without WBE was increased by presoaking them in water, a similar decrease was noted ('soak effect' or SE) WBE and SE could both be nullified by the addition of antibacterial antibiotics, and so were attributed to antagonism by saprophytic seed-borne bacteria Factors stimulating bacterial development (higher temperature and pH, addition of nutrients or bacteria) were found to increase WBE and SE; factors stimulating fungi more than bacteria decreased or eliminated it If one of both groups (bacteria or fungi) obtains the initial lead it will dominate and reduce the expression of the other group Elimination of bacterial antagonism results in higher percentages of both pathogenic and saprohytic fungi found The use of antibiotics eliminates bacterial antagonism as a source of variation Bacterial antagonism in the agar method is often less important due to low pH of the medium This offers an explanation for the higher agar than blotter percentages found for such an infection as Botrytis cinerea in flax seed The hypochlorite pretreatment customary for the testing of most seeds by the agar method also restricts bacterial antagonism Bacterial antagonism in agar tests may not only lower infection percentages found but also change the colony appearance The addition of a small quantity of an antibiotic to the agar medium eliminates it altogether The importance of the WBE and SE may vary with the sample, due to differences in the bacterial flora of the seeds Plating soaked seeds on agar media yields hardly any pathogen, but agar media with antibiotics which were routinely used in all further work, more or less nullify the previous SE Soaking in terramycin solution often gave increased percentages of the pathogen The same factors stimulating bacterial antagonism in blotter tests also favour it in sand and soil Chapter 4 starts with the observation that in case of Phoma valerianellae infection of corn salad seeds blotter tests with 2,4-D gave remarkably higher percentages than normal blotter tests This led to the realization of the importance of the factor 'host vigour' in incubation methods Various other treatments such as water soak, exhaustion, mutilation and freezing gave similar results The reduction (2,4-D), elimination (freezing) or circumvention (agar method) of host vigour often lead to higher percentages being found for seed-borne infections It also offers an explanation for the difference between blotter and agar test results for some infections Reduction of the host vigour causes a shift from symptoms of the disease to signs of the pathogen to be looked for at inspection The freezing of pre-incubated seed followed by a post-freezing incubation period (freezing method) was found to be promising for a number of infections For some infections (eg Helminthosporium spp) it simplifies inspection, no seedling structures being produced Provided bacterial development is checked by means of antibiotics, fungi grow easier and more abundantly, probably due to increased leachage of nutrients from seeds Fungal infections can therefore be more easily recognized and identified, and higher infection percentages may be found Some seeds which are rich in easily available nutrients (eg wheat) must be protected from air-borne contamination In the freezing method the trays with paper can be replaced by plastic sheets with depressions filled with liquid (containing eg antibiotics) for the seeds In chapter 5 it is observed that interfungal antagonism becomes more prominent when bacterial antagonism and host vigour are either not important or have been eliminated It is consequently especially a problem in the agar method Interfungal antagonism is influenced by incubation conditions, eg temperature Its reduction by the use of hypochlorite pretreatment is rather non-selective, eliminating also part of the pathogen, although it may be all right for such deep-seated infections as Ascochyta spp in pea and Phoma betae in beet seeds More selective is the 'dry heat' pretreatment advocated by MALONE (1962) for Havenae in oat seeds tested by the agar method Its use was extended to other Helminthosporium spp in oat and barley seeds but has the disadvantage of increased Mucor development in subsequent agar tests In blotter tests with dry heat pretreatment Mucor presented no problem, but the results were not superior to those of the freezing method A highly selective method is the use of peptone-PCNB agar for Fusarium spp In this method neither bacterial and fungal antagonism nor host vigour play a role, so that very high infection percentages may be obtained Tests carried out by this method are easy to prepare and to inspect Another way to combat interfungal antagonism is the use of growth-restricting agents, such as oxgall, in agar media This offered good prospects for the slow growing Septoria nodorum in wheat seed, which is otherwise easily suppressed by other fungi The use of oxgall eliminates the need of surface disinfection which is an advantage as light infections of Snodorum can be important Chapter 6 deals with measurement of the severity of infection Very light Fusarium infections of single seeds may be considered to be of little consequence Their elimination by hypochlorite pretreatment can therefore be accepted and may be used as a correction of the very sensitive peptone-PCNB agar method This led to considerations on the importance of inoculum potential and threshold level of infection Seed health data are usually given in terms of percentage of infected seeds Possible ways to correct them for inoculum potential were indicated, such as the use of pretreatments of standardized strength This could perhaps compensate for the elimination of such factors as antagonism and host vigour Chapter 7 describes experiments in which a large number of wheat seed samples containing Fusarium spp and Septoria nodorum were tested in various ways The results were then compared and correlation coefficients between them were computed Although the latter were low, they were generally significant The correlations of germination capacity with soil emergence decreased with temperature due to the presence of F nivale This pathogen only reduces emergence at lower temperatures, being of no consequence at higher ones Snodorum did not significantly reduce emergence in the samples used, although at lower temperatures it caused more abnormal seedlings to be produced S nodorum was always highly correlated with coleoptyle lesions The blotter test for Fusarium spp was shown to be very unreliable The symptoms are hard to judge so that errors of judgment are easily made the presence of the different Fusarium spp is not equally well indicated and other fungi eg S nodorum may interfere by producing the same symptoms The blotter test for Snodorum is only good for a number of cultivars that produce the characteristic protuberance symptoms For other cultivars the symptoms to be used are highly unreliable, especially if Fusarium spp are present, which usually is the case The agar method is therefore to be preferred, preferably without surface disinfection, but with eg, oxgall added to the medium It is suggested that due to the complex nature of the factors involved, which are moreover unpredictable the usefulness of correlation coefficients for seed-borne infections is very limited Their main use may be in the comparison of various methods with seed ling performance in conditioned soil tests In chapter 8 it is concluded from the preceding that the incubation conditions applied in seed health testsdo not only affect the expression of the pathogen in a direct way They also affect the pathogen indirectly via the seed biotope (seed microflora and host seed or seedling) The seed biotope varies with the sample so that the most important source of variation is presented by the ecology of the germinating seed itself Elimination and circumvention of these biotic factors, which also decreases the chances of errors of judgment, seem to offer the best prospects for the development of simple, cheap, fast and reproducible methods Application of correction factors for inoculum potential may be important for a number of infections (eg Fusarium spp in cereal seeds) Tolerances if used may be regarded as a correction for local agricultural conditions and should be based on the methods used for testing

Germination, Growth, and Ecology of Sicklepod'

Abstract: Germination, growth. and potential phytotoxicity of sickle- pod (Cassia obtusifolia L.) were studied. Seed germination occurred in the tenmperature range from 18 to 36 C, but rapid seedling growth occurred only between 30 and 36 C. Seed dormancy caused by a waxy coat resulted in only 15% germination in soil over a 12-month perio(l. A 1:15 (g/ml) water extract of sicklepod tops inhibited ger- mination of cotton (Gossypiuml hirsutirn L.) and oat (Avena sativa L.) seedl. Incorporation of sicklepod residues in soil reduced germina- tion of cotton seed but increased persistence of sericea (Lespedeza cauneata (Dumont) G. Don.) and crimson clover (Trifolium incar- tnatunttt L.) because damping-off was almost eliminated. There was evidence in nutrient cultures that sicklepod released a phytotoxic residuie from its roots, reducing growth of cotton but having no effect on soybeans (Glycine max (L.) Merr.). Sicklepod grew well in soils ranging from pH 3.2 to 7.9. Sicklepod response to N, P, and K levels was similar to cotton and higher than that of soybeans.

Reversal of (±) ‐Abscisin II Induced Inhibition of Lettuce Seed Germination and Seedling Growth by Kinetin

Abstract: Observations have been made on the effect of synthetic, (±)-abscisin II (dormin), alone and in combination with gibberellin, kinetin and indoleacetic acid, on seed germination and seedling growth of two strains of lettuce, cv. Attraktion and cv. Hohlblattriger Butter. (±)-Abscisin II inhibited seed germination and seedling growth in both strains. The inhibitory effect of abscisin II on seed germination as well as seedling growth was completely overcome by kinetin in both dark and light. Gibberellic acid, on the other hand, proved ineffective in exerting its influence on seed germination in presence of abscisin II but affected subsequent seedling growth as usual. Indoleacetic acid was found to be least potent in reversing abscisin II caused inhibition of seed germination and seedling growtb. It is concluded, that like its effect on certain other naturally occurring inhibitors of seed germination, kinetin can effectively undo the inhibitory effects of abscisin II in these growth processes.

Germination Behavior of Salsola as Influenced by Temperature, Moisture, Depth of Planting, and Gamma Irradiation1

Abstract: Salsola kali, L. seeds contain fully differentiated seedlings and these uncoil in minutes with favorable temperature and moisture. If germinated on the soil surface, the uncoiled seedling will dehydrate and die if it cannot push its roots into the soil. Germination is most favorable for seeds covered with soil. For this reasons the species generally appears only on disturbed soils. Seeds germinate satisfactorily at 17 C and at .1% soil moisture in Yolo loam stabilized with krilium and seedlings emerged from a planting depth of 7.5 cm. Evidence obtained with gamma irradiation from a Co/sup 60/ source indicates that germination consists of rapid cell elongation in response to moisture and that new cell division is not necessary to the process. Irradiation of seed at levels above about 50,000 R impaired cell division but levels of over 400,000 R were necessary to cause additional germination injury.

Effects of Soil Salinity and Growth Regulators on Germination and Seedling Metabolism of Wheat

Abstract: Germination studies were carried out with the wheat varieties NP823, Karchia, Sonora 63, Sonora 64, Mayo 64 and Lerma Rojo in artificially salinized soil maintained at ECe 2, 8, 12 and 16 mmhos/cm at 25°C. Early seedling growth and metabolism of variety NP 823 was studied in salt solutions alone and with addition of the growth regulators GA3 and Cycocel (2-chloroethyl trimethylammonium chloride). Soil salinity both depressed and delayed the germination. Among the varieties tested NP 823 and Karchia were relatively less susceptible to salt injury while Lerma Rojo exhibited a maximum susceptibility. Salt supply also brought about a reduction in the early seedling growth, the release of reducing sugar and the amylase activity. The adverse effect on amylase activity was not mediated through the synthesis of enzyme protein but by an inhibition of the enzyme activity. Exogenous supply of GA3 counteracted the adverse effect of salt on amylase activity and the release of reducing sugar but not on the early seedling growth.

Effect of Soil Salinity on Germination and Survival of Some Steppe Plants in Washington

Abstract: Salt tolerance at germination and the capacity of the established plants to endure gradual salinization of the soil were studied in Agropyron spicatum, Artemesia tridentata, Elymus cinereus (from saline and non—saline habitats), Lepidium perfoliatum (from saline and non—saline habitats), and Typha latifolia. Percentage germination decreased with increasing salinity. All species were less tolerant of salinity at germination than they were at the seedling stage, if salinization of the culture medium was gradual. An abrupt rise in salinity resulted in death of all species. Of all the species tested Lepidium perfoliatum demonstrated the greatest potential for ontogenetic osmoregulation. In general, the response of the established plants corresponds well with the species behavior in the field. Adverse environmental factors, such as a predominance of Na2CO3, probably results in restricted distribution of Typha latifolia and also keeps Agropyron spicatum from colonizing saline areas. Seeds of Lepidium perfoliatum from saline habitats were more tolerant of salinity than those from non—saline habitats, indicating an ecotypic specialization in this species. Populations of Elymus cinereus from saline and non—saline habitats did not differ in this respect.

Nutritional control of the correlative inhibition between lateral shoots in the flax seedling (Linum usitatissimum)

Abstract: When the epicotyl of the flax seedling is decapitated one of the two shoots produced at the cotyledonary node tends to inhibit and may completely suppress the growth of the other. By growing the seedlings in sand culture with a controlled mineral nutrient supply it was shown that (a) the inhibiting influence of the dominant shoot was inversely related to the nitrogen level; (b) the inhibited shoot could be released from inhibition by increasing the nitrogen supply; (c) the removal of the dominant shoot was followed within 12 h by an increase in the total nitrogen content of the inhibited shoot; (d) a similar control of inhibition could be obtained by varying the phosphorus supply. These results are consistent with the hypothesis that this form of correlative inhibition is due primarily to competition between the shoots for a limited mineral nutrient supply.When one of the cotyledons was either covered or removed its axillary bud was inhibited by the shoot in the axil of the untreated cotyledon. The degree...

Factors Influencing Pre‐emergence Mortality in Peas

Abstract: SUMMARY Seedling emergence of 25 samples of wrinkle-seeded peas (Pisum sativum L.) was determined in unsterilized soil and sterilized sand at 15°C in the laboratory, and in a spring sowing in the field. Seed exudate from the seed samples was examined by steeping seed in water for 24 hours and measuring the electrical conductivity of the steep water and its soluble carbohydrate content. Significant correlations were found between the amount of exudation and the number of viable seed in the test samples (negative) and between the amount of exudation and the predisposition of the viable seed to pre-emergence mortality (positive). Samples containing a large proportion of seed that readily exuded into steep water showed poor emergence in soil, both in the laboratory and in the field. Pythium spp. were isolated from ungerminated seeds taken from the field and laboratory soil. The role of exudates in stimulating fungal pathogens in soil is discussed as a possible explanation for the association between exudation and predisposition to pre-emergence mortality. A routine test for indicating seed samples of potentially low field emergence is suggested.

Factors Limiting the Survival of Corynephorus canescens (L.) Beauv. in Great Britain at the Northern Edge of Its Distribution

Abstract: Corynephorus canescens presents two distributional problems in Great Britain; first, as a species with restricted distribution, and second, as one at the northern edge of its distribution. The first problem may be related to the past history of any one dune system and in particular the continuance in time and space of open sandy habitats of intermediate stability; the possible factors limiting Corynephorus at the northern edge of its distribution are considered in the body of the paper. The maintenance of Corynephorus populations is dependent on successful production and dispersal of seed, germination and seedling establishment. Reproductive capacity and seed viability are high. No dormancy mechanisms have been detected. Seed after-ripening is little affected by low temperature (0'C) and the seed is fully ripe eight weeks after anthesis. Germination is slowed down at temperatures below 15'C. Germination in the field is controlled by the availability of moisture for imbibition and its rate by temperature. The later the emergence date of seedlings in the field, the lower the chances of seedling survival. Seedling mortality occurs at a number of stages. It is concluded that the climate beyond the most northerly locality of Corynephorus in Great Britain (57O45' N) is severe enough to have a cumulative effect on flowering date and seed germination sufficient to postpone emergence date of the seedlings beyond the critical time for their survival. Pe3IoMe Bonpoc o pacnpocTpaHeHHH Corynephorus c nescens B BeJIH4o6pHTaHHH pacc;aTPHBaeTCJR B ABYX acneKTax: Bo-fepBbIX, 3T0 BHa c orpaHHxIeHHbIM apeaJioM, BO-BTOpb6X, BejiHKco6pHTafHH1 ipeACTaBjiAeT ceBepy1io o6nacTE apeajia J aHHoro BHXqa. JlepBar npo6iieMa cBs3aHa c H3y'IeHHeM BO3HHKHOBCHHSI H pa3BHTHR A1OHHOrO jiaHAina4)Ta, B xiaCTHOCTH C BOnPOCOM o XJIHTejibHOCTH cyLLIeCTBOBaHHA BO BPeMeHH H npocTpaHcTBe OTKpbIThIX nec:IaHbIX MecTOO6HTaHHtA H HX cTa6HUnbHOCTH. B CTaTi6e o6cyxcaaIoTcJq 4)aKTopbI, onpegenimoLUe pacupeAeneHsHe Corynephorus B ceBepHoll 4acTH ero apeana. COCToaqHHe nonyJIslIHti1 Corynephorus 3aBHCHT OT riPOaYKiHIKH H pacnpocTpaHeHHH ceMAIH, a TalKxe OT YCJIOBHfi[1 popaCTaHHR3 ceM5H. PeupoxyiTHBHas cnoco6HocTb H XKHWHecnoco6HOCTb ceMS1H aOBOJ16bHO Bb6COKH. JlepHoEbI noKOSI y AaHHoro BHIAa He YCTaHOBJIeHbI. CeMeHa nocie Co3pesBHHI 110I'TH He tIYBCTBHTeJThHbl K AeticTBHIO HH43KOtI TeMnepaTypbl, OHH nonHOCTMIO c03peBaio) 'epe3 8 HeAenj1i nocxie JiBeTeHH,I. BcxoxeTT, ceM51H 3aMexursieTCR UPH TemnepaType HH)xKe 150C. BcxoxceCT CMesH B flOj1eb61X YCJIOBHIAX 3aBHCHT OT KoJIHIYeCTBa AocTynHoi BjiarH, a CKOPOCTb npopaCTaHHui 3aBHCHT OT TeMnepaTypb6. xeM fo303AHee CPOKH IO5IBJeHHSI ripopOCTKOB, TeM meHee 6naronpHsTHB, ycnoBsHi AXIR HX pa3BHTHR. OnpeaeneHa rH6eJIb npOPOCTKOB Ha pas3HbIX (aaax pa3BHTHSI. YcTaHOBjieHO, MTO KJIHMaTHIqeCK4e YCJIOBHS ceBepHee rpaHHnbi apeana Corynephorus B BenIHKo6pH4TaHH1H /57 O/45' c.i., OKO[O JIoccHMyTaf CIHIIIKOM CyPOBbI, H CPOKH UBeTeHHA paCTeHHH H nOqBneHHSI nPOPOCTKOB BbIXOAST 3a npeAejibi KPHTH'IeCKHX nepHO)AoB. Manuscript accepted February 1968.

Morphogenetic aspects of a leafless mutant in tomato i. general patterns in development

Abstract: A B S T R A C T The embryo of the reduced form of the lanceolate mutant in tomato fails to undergo the heartshaped stage of development. Cells in the shoot apical region of this leafless mutant lose their meristematic character and develop into mature parenchyma during embryogenesis. This early loss of meristem tissue leads to the determinate growth which is evident in the seedling. In contrast to normal, starch grains are visible with the light microscope in cells of the shoot tip of the mutant hypocotyl from early embryogeny up to and including the seedling stage, and protein bodies are abundant in the same tissue of fully developed mutant embryos. The shoot apical region in homozygous mutant embryos with cotyledons or cotyledon-like structures exhibits some cytochemical and morphological similarity with the normal shoot apex. Morphological variation in these forms appears to be in a continuous pattern. The extent of their development and consequent longevity is related to possible differences in rates of cell expansion and variation in environmental factors during the early stages of embryogenesis. LANCEOLATE is a leaf-shape mutant in tomato (Lycopersicon esculentum Mill.) which results from the action of a single gene in the heterozygous condition. The lanceolate phenotype is characterized by a simple, lanceolate leaf and has been described by Mathan and Jenkins (1962) and Stettler (1964). When the La gene is present in double dosage, the resulting form is variable. The above workers recognized three forms in the homozygous mutant: narrow, with small and extreme lanceolate leaves, weak apical dominance and abortive inflorescences; modified, with a single fleshy cotyledon with or without a bud-like structure at its base; and reduced, a hypocotyl which lacks cotyledons, foliage leaves, and an organized shoot apex. Studies of lanceolate have been primarily biochemical and genetical in nature (Mathan and Cole, 1964; Mathan, 1965a, b) and have centered on the heterozygote, although some interest has been shown in the narrow and reduced forms of the homozygous mutant. Such studies have revealed higher activities of four different oxidative enzymes in the mutants. The enzymes involved are: catalase, laccase, peroxidase and tyrosinase. Some evidence was obtained for a suggested link between gene action and external form when the extreme forms

The growth and development of some grass species under competitive stress

Abstract: Three experiments were carried out in a semi-controlled glasshouse environment to determine the response of individual plants to competition; (i) between seedlings of different species, (ii) between seedlings derived from seeds of differing sizes within a species, and (iii) between seedlings and established plants. Differences were detected in seedling competitive ability between species and between plants derived from differing seed sizes. In associations of species of very high and very low competitive ability the differences in competitive ability were accentuated by an increase in plant density. Established plants of Phalaris coerulescens were less aggressive to seedlings growing in close proximity than were plants of Lolium rigidum and H1 ryegrass. Despite the early death of established swards of L. rigidum, and the consequent removal of competitive stress, there was no rapid increase in the growth and development of seedlings in these swards. Possible mechanisms causing this effect are discussed. There was evidence of a specific relationship between the species of the established sward and the seedling species, in particular seedlings of HI ryegrass were particularly susceptible to competition from established plants of their own species. Dry weight per plant, tiller production, rate of leaf appearance and leaf size were ail affected by competition between seedlings; however, tiller production was generally more severely affected than rate of leaf appearance and leaf size. Dry weight per plant, tiller production, seedling height, number of leaves per tiller and number of seeds per seedling were all affected by competition from established plants.

Low-temperature growth responses of the tomato

Abstract: The effects of low temperatures on several growth phases of the tomato were studied. The tests, each conducted over a 2-week period, included seed germination at 8.5 °C, rate of seedling growth at a night temperature of 10 °C, root and top growth of plants in soil at 15 °C, and fruit set at a night temperature of 4.5 °C.Varietal response to growth rate at low temperatures differed in all phases studied, and varieties that performed well in some phases did not always perform well in others. Of the varieties studied, six grew well under most of the low-temperature conditions. These were: Earlinorth, Bonita, Azerbidzivisky, P.I. 205040, P.I. 280597, and Cold Set.

The Gibberellin Content and early Seedling Growth of Plants of Phaseolus vulgaris Treated with the Growth Retardant CCC

Abstract: 1. The effect of CCC applied at 10-2 M to plants of Phaseolus was followed. 2. Dry seeds did not contain extractable gibberellin. During germination of control plants gibberellin content increased markedly between days 3 and 4; but then tended to decline. For plants which emerged into light conditions, synthesis of gibberellins was noted. Treatment with CCC at planting delayed the appearance and reduced the level of extractable gibberellins, but did not prevent their appearance in appreciable quantity (up to 7.2×10-8 g plant). CCC treatment on day 7 inhibited the gibberellin production noted in light-grown plants. 3. Three zones of gibberellin activity were found on the thin layer chromatograms of plant extracts. Two of these zones corresponded with the running position of gibberellins A 8 and A 5 in our solvent system. 4. Treatment with CCC retarded the loss of fresh, dry and ethanol-insoluble weight of the cotyledons, which also showed, on a unit weight basis, a lower respiration rate. Hydrolytic activity of the cotyledons, as estimated by amylase activity, was slightly lower in treated cotyledons, which also showed a lower rate of loss of insoluble nitrogen. 5. Failure of the stems to elongate in treated plants was associated with a reduction in stem dry weight and an increase in leaf dry weight. Final dry weight of treated and control plants was similar. 6. It is suggested that CCC acts by inhibiting gibberellin synthesis. Because of this inhibition of synthesis, the onset of hydrolytic activity in the cotyledons is retarded so that liberation of preformed, bound gibberellin is delayed but not prevented. Failure of the stem to elongate is attributed to lack of gibberellin, and it is postulated that because of this, dry matter from the cotyledons is diverted to the leaves.

Fusarium diseases of cereals: III. Water relations and infection of wheat seedlings by Fusarium culmorum

Abstract: The incidence of pre-emergence death of wheat seedlings due to Fusarium cuimorum (W. G. Sm.) Sacc. is higher in dry as compared with wet soils because of longer time elapsing between sowing and emergence of seedlings above the soil. Soaking Viking wheat seeds for 3 h in water prior to inoculation with F. cuimorum or sowing in inoculated soil increased seedling vigour, so that seedlings escaped infection leading to pre-emergence death, and the severity of disease was reduced. Pre-emergence death was reduced by soaking seeds for 1–12 h as compared with seeds soaked for shorter or longer periods or unsoaked seeds. Disease incidence was influenced by the temperature of the water in which seeds were soaked. After soaking seeds in various concentrations of gibberellic acid the resulting seedlings emerged through the soil more rapidly than those from seeds soaked in water but a combination of factors caused more disease to develop in the former. In the field, wheat plants of the varieties Viking and Jufy I developing from seeds soaked for 3 h in water were less susceptible to both the seedling and foot rot stages of the disease than those from unsoaked seeds. Plants developing from inoculated seeds produced fewer tillers and the ears emerged 10–14 days earlier than in plants from uninoculated seeds. Soaking seeds for 3 h before inoculation increased the seed yield of the resulting plants.

Phytotoxicity of Plant Materials on Seed Germination of Crownvetch, Coronilla varia L.

Abstract: Phytotoxic potential of six crop and four weed species was determined on crownvetch. Water extracts of Virginia pepperweed, evening primrose, crabgrass, and crownvetch were most toxic to seed germination. Tall fescue and weeping lovegrass were least toxic. Extracts from aerial portions were more inhibitory than those from roots. Crown vetch was less tolerant of high osmotic pressure than was crimson clover, but this did not explain the strong inhibition of the former species by certain plant extracts. Pepperweed residues incorporated into soil for 10 weeks were toxic to crownvetch seed germination. Kobe lespedeza residues incorporated into soil did not affect percent germination but decreased seedling growth. Pepperweed extract inhibited seed germination of tall fescue, ball clover, sericea, and Kobe lespedeza. It was toxic to crownvetch at a dilute concentration of 1:150 (w/v). The toxic substance occurred in all parts of the plant and was not affected by drying temperature. Pepperweed extract was toxic to five fungi. The phyto- and fungitoxicity of pepperweed may be of significance in competition with other plant species.

Northern Red Oak Seedling Growth Varies by Light Intensity and Seed Source

Abstract: --Northern red oak seedlings from each of three seed sources were subjected for one growing season to one of four intensities of light: full light, 70 percent light, 37 percent light, and 8 percent light. Seedlings grown in the open were taller than those grown in the shade and had more, generally heavier leaves. Height and leaf growth decreased as the amount of light reaching the plants decreased. Seed source, another important factor affecting growth, was related to height growth, number of leaves per seedling, acorn weight, and percent of multiple stems. Forty-one percent of the seedlings from one source had multiple stems, while only 11 percent and 4 percent of the seedlings from the other two sources had multiple stems. In seeking to determine light requirements for seedlings of northern red oak (Quercus rubra L. 1, we found that seedlings exposed to open sunlight grew taller in the first year than did those subjected to varying degrees of shade. At a time when many forest landowners are shifting to even-age management and its associated heavy harvest cuts, it is reassuring to observe red oak seedlings growing well in the open. This phenomenon does not preclude the possibility that under certain conditions the temperature or soil moisture associated with shade might improve growth. Nevertheless, the study results show that shade itself is not necessary to the growth of northern red oak. To determine whether light requirements varied according to seed source, acorns were collected from three widely separated northern red oaks (table 1). All acorns were stored in moist sand at 40’ F. Before they were planted on March 15, 1966, the acorns were cleaned and weighed so that any correlation between acorn weight and growth could be observed. Table 1. --Description of seed source trees Tree Age Merchantable height Diameter Site elevation Average acorn weight Years Feet Inches Feet Grams 150 16 9 5,000 5.5 200 40 30 3 ,300 10.4 70 2 4 16 2 ,700 7.1 Seedlings from each of the three seed sources were subjected to one of four intensities of light: 8 percent sunlight (heavy shade), 37 percent sunlight (medium shade), 70 percent sunlight (light shade), and full sunlight (no shade). Light intensity was regulated on each plot by plastic screens which controlled the amount of light reaching the plants (fig. 1l.l Figure 1. --Study layout showing shade apparatus and seedlings. On April 29, when the spring foliage in the adjacent forest began to cast a sign%cant amount of shade, the plastic screens were set in place. These screens were removed on October 12, a date roughly corresponding with the annual fall leaf .drop. During the growing season, the seedlings were watered frequently to prevent variation in soil moisture between treatments from becoming a major factor affecting growth. The seedlings grown in the open, in particular, dried quickly. Near the end of the growing season the number of leaves and stems per seedling were counted. At the same time, two disks of leaf tissue were taken from each seedling. The disks from each plot were grouped by seed source, ovendried, and weighed. At the end of the growing season seedling height was measured. In the case of multiple stems, the height of the tallest stem was recorded. RESULTS Regardless of seed source, those seedlings grown in open sunlight were considerably taller, had more and thicker leaves, and were generally healthier than those grown in the shade (tables 2, 3, and 4). As the amount of sunlight reaching the plants decreased, height and leaf growth also decreased. Seedlings receiving a low intensity of light (8 percent), comparable to the light under a natural mature oak stand, were only 60 percent as tall as seedlings grown in the open and 84 percent as tall as seedlings receiving ‘Because future plans for the study include determining the effect of release from shade on seedling growth, more replicates of the various shade treatments were set up than of the full sunlight treatment. This disproportion in the number of plots for the shaded and unshaded seedlings prevented our subjecting the data to an analysis of variance. a medium intensity of light (37 percent). Seedlings receiving a low intensity of light had about half as many leaves as did seedlings grown in the open and, based on the ovendry weight of the respective leaf disks, only 80 percent of the leaf weight per unit area. Table 2. --Height of northern red oak seedlings in relation to light treatment and seed source Seed source Treatment Full ‘70 percent light 37 percent light 8 percent light Average light (light shade) (medium shade) (heavy shade) -----------------lnchee----------------Tree 1 6.77 5.03 5.17 4.94 5.48 Tree 2 9.40 7.58 7.23 5.80 7.50 Tree 3 11.40 8.87 1.25 5.72 8.31 Average 9.19 7.16 6.55 5.49 7.09 Table 3. --Average number of leaves per northern red oak seedling by light treatment and seed source Seed source Full light Treatment ‘70 percent light 37 percent light 8 percent light Average (light shade) (medium shade) (heavy shade) ------------------Number----------------Tree 1 10 7 7 6 7 Tree 2 14 12 11 8 11 Tree 3 13 11 8 6 10 Average 12.3 10 8.7 6.6 9.3 Table 4. --Ovendry weight of leaf disks per seedling by light treatment and seed source Seed source Full light Treatment 70 percent light 3’7 percent light 8 percent light Average (light shade) (medium shade) (heavy shade) _---_---------Milligrams _ _ _ _ _ _ _ Tree 1 11.49 10.48 9.97 9.26 10.30 Tree 2 10.74 12.07 9.78 8.28 10.21 Tree 3 10.75 11.88 9.45 8.78 10.21 Average 10.99 11.14 9.73 8.17 10.24 Seedling response also varied according to seed source. Acorns from tree 3 produced seedlings 14 times as tall as seedlings produced from tree 1 (table 2). A high correlation also exists between seed source and number of leaves per seedling (table 3). The large number of leaves per seedling shown for seedlings from tree 2 can be partially explained by the high number of multiple stems produced by acorns from that tree. Forty-one percent of the seedlings from tree 2 had multiple stems as compared with 11 percent of the seedlings from tree 3 and 4 percent of those from tree 1. Another factor associated with seed source is the average weight of acorns. Acorns from tree 1 averaged only 5.5 grams while those from tree 3 averaged 7.1 grams, and those from tree 2 averaged 10.4 grams. It is possible, therefore, that some of the differences in seedling response associated with seed source were due to acorn size. Weight variation of acorns from a single tree, however, was not generally associated with variation in seedling height growth. Regressions of seedling height on acorn weight were computed for each of the 12 treatment-seed source combinations; only two of these regressions had b coefficients significant at the 5-percent level. DISCUSSION Perhaps the best lesson to be learned from this study and other published results is that the various oak species vary in their response to light, and each must be studied and managed on an individual basis. Kramer and Kozlowski2 have stated that, generally, high light intensities increase root-shoot ratios, leaf thickness, number of stomata, and cell wall thickness. KozlowskP found that seedlings of overcup oak (Quercus lyrata Walt. 1 are shorter but heavier when grown in full sunlight than when grown in the shade. Jarvis4 found that for sessile oak (Quercus petraea (Mat;. ) Liebl. 1 shading increased height, leaf area, leaf area ratio, and chlorophyll content but decreased leaf thickness, root weight, root-stem ratio, net assimilation rate, and relative growth rate. Data from this study show rather conclusively that northern red oak seedlings do not require shade during their first year. The 2to 4-inch average height advantage of seedlings grown in the open over shaded seedlings may in some cases be of no practical importance. On the other hand, there may be cases where an extra 2 inches would be the key to survival by keeping such seedlings just above competing growth. The variation in response for seedlings produced from different trees may also have practical significance. Producers could grow better oak seedlings by separating acorns according to source and eliminating from future collection those trees that produced seedlings with poor growth or multiple stems. The same selectivity should be maintained for direct seeding. Germination tests could be run on a few acorns from potential parent trees before the acorns were seeded; subsequent acorn collection could then be confined to the best trees. Much work remains to be done before forest biologists can be confident that they know the environmental requirements for the various oak species. The study reported here is part of a comprehensive study of the light requirements and response to release of northern red oak. 2Kramer, P. J., and Kozlowski, T. T. Physiology of trees. 642 pp. New York: McGrawHill Book CO. 1960. SKozlowski, T . T . Light and water in relation to growth and competition of Piedmont forest tree species. Ecol. Monogr. 19: 207-231. 1949. 4Jarvis, P. G. The adaptability to light intensity of seedlings of Quercus petraea (Matt. ) Liebl. J. Ecol. 52(3): 545-571. 1964. Charles E. McGee, Silviculturist Asheville, North Carolina

The Influence of Soil Moisture Deficits on Seedling Growth of Three Coniferous Species

Abstract: Rising 3-0 seedlings of red pine, white spruce and larch were subjected to two drought periods in a growth chamber. The four treatments were control, 1, 6, and 15 atmospheres of soil moisture tension.The 15 atmospheres treatment affected the length of terminal leader and the stem diameter of red pine and larch, but not of white spruce. The needle length of red pine was affected by all three drought treatments.

The growth of the young coconut palm (Cocos nucifera L.). I. The role of the seed and of photosynthesis in seedling growth up to 17 months of age

Abstract: The growth of coconut seedlings and the changes occurring within the seed were studied over a period of 17 months from the germination of the coconuts. Removal of the husk prior to germination made possible an estimate of the endosperm content of each seed and also permitted the exact date of germination to be observed. Seedlings were grown with a non-limiting supply of water and nutrients; 63 seedlings were harvested on each of 10 occasions to enable a growth analysis to be made. A high initial relative growth rate, arising through contributions by the endosperm, fell at 4 months to a level which remained roughly constant to 17 months. By 4 months the haustorium had reached its full size, but thereafter the relative contribution from the endosperm via the haustorium was much diminished. Between 4 and 15 months a gradual change over to full dependence on photosynthesis took place. By 17 months less than 10% of the endosperm remained in the nut. The rate of leaf production was constant with time, but the leaf area increased almost exponentially. There was some indication of a positive relationship between net assimilation rate and solar radiation. Some conclusions are drawn concerning cultural methods with young coconuts.

Effects of Herbicides on Seed Germination and Early Seedling Development of Pinus resinosa

Abstract: Herbicides varied greatly in their influence on seed germination and early seedling development of Pinus resinosa Ait. At concentrations up to 4,000 ppm, atrazine, monuron, and DCPA placed in direct contact with seeds did not significantly influence seed germination. In contrast, NPA, CDEC, EPTC, CDAA, and 2,4-D at the same concentrations suppressed germination in the following order of decreasing inhibitory effect: CDAA > 2,4-D > EPTC > CDEC > NPA. Active ingredients alone, except those of CDEC and EPTC formulations, affected germination similarly to the commercial formulations. Seed germination was higher when seeds were treated with active ingredients alone of CDEC or EPTC than when treated with commercial formulations. Growth of young red pine seedlings was inhibited variously by NPA, CDEC, CDAA, EPTC, and 2,4-D. The most conspicuous effect of herbicide treatment was inhibition of cotyledon development. Plants treated with CDEC or EPTC had fused cotyledons. Those treated with the 2,4-D had swollen ste...

Effect of pretreatment of pine seeds with herbicides on seed germination and growth of young seedlings

Abstract: The effect of 24-hour pretreatment of Pinus resinosa Ait. seeds with herbicides, before the seeds are planted in soil, was studied on seed germination and seedling development over a 34-day period. Atrazine, simazine, or propazine at 200, 500, or 1000 p.p.m. did not affect seed germination significantly. At 500 and 1000 p.p.m. CDEC and EPTC had little or no effect on seed germination whereas CDAA and 2,4-D markedly inhibited both early and final germination. Atrazine and simazine were very toxic to young pine seedlings, with toxicity proportional to herbicide dosage. In contrast to atrazine and simazine, propazine did not kill seedlings during the 34 days of the experiment. At 500 p.p.m. CDEC and EPTC began to kill young seedlings at 24 days; 2,4-D at 27 days. CDAA, which had suppressed seed germination greatly, did not kill young seedlings. Marked morphogenic changes in seedlings were caused by pretreatment of the seed with EPTC, CDEC, or 2,4-D. CDEC and EPTC caused fused cotyledons; 2,4-D caused swollen...

The Environmental Tolerance of the Seedling Stage of Sequoiadendron giganteum

Abstract: Studies of the environmental tolerance of the seedling stage of Sequoiadendron giganteum determined the influence of light in- tensity, soil moisture, and soil pH on the growth and survival of seedlings two to five years old. The young trees are more drought resistant than previously thought, and capable of growing and surviving under a wide range of soil moisture and shading conditions.

Rasch ablaufende Änderungen im Gehalt an löslichen Zuckern und Zellwandkohlenhydraten bei der phytochrominduzierten Photomorphogenese des Senfkeimlings ( Sinapis alba L.)

Abstract: Short term changes in the soluble sugar, starch, and cell-wall carbohydrate content of the mustard seedling have been studied in the different organs during phytochrome induced photomorphogenesis in continuous far-red The program was: imbibition of seeds →36 hrs dark → far-red irradiation Kinetics have been followed up to 12 hrs after the onset of irradiation There are no substantial changes in carbohydrate content in the cotyledons and the radicle In the cotyledons in far-red after a lag-phase of 3 hrs, there is a decrease in oligosaccharide content, and after a lag-phase of 6 hrs, an increase in cell-wall synthesis The reducing sugar and starch content is not altered upon irradiation In the radicle immediately after the onset of far-red, there is a temporary rise in the reducing sugar and cell-wall carbohydrate content However, 6 hrs later the values in far-red again parallel those of the dark control The important phytochrome dependent changes take place in the hypocotyl In far-red after a lag-phase of 3 hrs the glucose accumulation is markedly retarded, the sucrose and starch content no longer increased, and the fructose content even decreases below the 3 hrs value The glucose: fructose ratio, which is constant in dark, is shifted in favour of glucose The lag-phase of phytochrome controlled hypocotyl elongation is about 1 hr, the lag-phase of the inhibition of cell-wall carbohydrate synthesis is in about the same order of magnitude There seems to be neither any immediate connection between sugar content and cell-wall carbohydrate synthesis, as shown by the difference in lag-phases, nor does there seem to be any direct relationship between hypocotyl inhibition and overall synthesis of cell-wall material The relative inhibition of cell-wall synthesis is less than one third of that of hypocotyl elongation (Figs 5,6) Apparently phytochrome controls hypocotyl elongation by influencing the cell-wall structure In spite of the fact that fat degradation is higher in far-red than in dark and respiration higher in dark than in far-red (Friederich, 1968), 6 hrs after the onset of far-red the increase of total carbohydrate content declines compared with that in dark This finding leads to the conclusion that the efficiency of the fat-carbohydrate-transformation is higher in dark than in far-red

Effects of seed treatments with gibberellic acid on subsequent growth of some eucalypt seedlings

Abstract: Summary Germination of seeds of Eucalyptus regnans and E. pauciflora in 50 mg/1 gibberellic acid markedly affected seedling growth. These effects included: stimulation of leaf production and shoot extension growth; slight reduction of root growth; alteration of the root/shoot ratio, and leaf shape; reduction in total dry weight and leaf thickness. Gibberellic acid affected leaf growth through reduced cell division. Stimulation of growth of E. camaldulensis hypocotyl by seed treatment with gibberellic acid could also be attributed to changes in cell division. No evidence of interaction between gibberellic acid and auxin was obtained. These results are discussed in relation to effects of gibberellic acid on other plants and tissues, and it is suggested the responses are explicable in terms of mobilization of food reserves.