Showing papers on "Seedling published in 1971"

Seed germination response and evidence for height ecophenes in spartina alterniflora from north carolina

Abstract: A B S T R A C T A study was conducted to determine germination response to temperature and salinity and seedling response to salinity by three height forms of the salt marsh grass Spartina alterniflora Loisel Germination tests showed that seeds cannot withstand drying at moderate temperature, as viability was lost within 40 days in seeds stored dry at 72 F Cold storage at 43 F is adequate to prevent desiccation up to 40 days, but after 8 months viability is lost Viability is retained at least 8 months when seeds are stored in sea water at 43 F Germination response was good in a 65-95 F alternating diurnal thermoperiod but was poor in a 72 F constant thermoperiod Germination response to salinity was an inverse curvilinear relationship with germination inhibition at high salinities apparently due to osmotic effects The maximum tolerance limit for germination lies between 6 and 8 % NaCl Seeds from short, medium, and tall plants responded similarly in storage and temperature studies However, in salinity studies, seeds of the Ocracoke Island short form and the Oak Island tall form performed best A logarithmic curve best described seedling growth response to various NaCl levels Growth response as measured by seedling dry weight was best in 05 % NaCl solution Seedlings grew taller in both 05 and 10 % NaCl than in 0 % NaCl No significant difference in seedling growth response due to height form of the parent plant was detected Thus, on the basis of germination and seedling responses, the height forms of S alterniflora in North Carolina salt marshes are best described as ecophenes

A Dynamic Analysis of Age in Sugar Maple Seedlings

Abstract: Age data from populations of sugar maple (Acer saccharum Marsh.) seedlings in southern Wisconsin were used to investigate two plant—population models: a negative exponential model and a power function model. A weighted death probability was calculated and compared to densities of potential germinants, and the influence of seed—crop numbers on stem density was analyzed. The power function model, implying a decreasing mortality rate as the seedling ages, is a good model for describing population dynamics of sugar maple seedlings. Seed crops and potentially viable seeds appear to have no effect on the numbers of stems remaining in the population after several years. However, the density of the initial input into the population system does affect the probability of a seedling surviving during its germination year. See full-text article at JSTOR

Environmental Factors Affecting Seedling Establishment of the Black Mangrove on the Central Texas Coast

Abstract: The effects of salinity, water turbulence, water depth, and temperature on the establishment of seedlings of black mangrove (Avicennia germinans L.) on the central Texas coast were evaluated in the laboratory. Salinity was not the chief factor limiting seedling establishment, because seedlings rooted in distilled water and in salinities approaching twice the concentration of sea water. Water turbulence, either of distilled or sea water, inhibited root and seedling development. Seedlings tumbled for as much as 12 weeks showed rapid root development when subsequently stabilized. Various water depths promoted extensive root systems, but seedlings did not become established until water depth was reduced to 5 cm or less. High temperature treatment, exposure to 39 degrees —40 degrees C for 48 hr, was lethal to stemless seedlings, but not to seedlings with stems and roots. The results suggest that vivaparous development in this A. germinans population phenologically timed by environmental relations during winter and early spring as a protection against the lethal effects of the high temperatures that prevail on beaches and in shallow water during late spring and summer.

Fate of Exogenous DNA in Arabidopsis thaliana

Abstract: It has been shown that when Arabidopsis seeds are incubated with different heteropycnic labelled DNA during the first 4 days of germinating, large fragments of exogenous DNA are taken up by the seedling plant tissues (cotyledons and rootlet) and remain polymerized and double-stranded during the entire growth period. Only a small percentage of the population of exogenous DNA molecules appears to be destroyed and reutilized for DNA synthesis de novo. Most of the exogenous DNA remains free or becomes integrated with the Arabidopsis DNA as double-stranded molecules, not separable by alkali denaturation, but easily separable by ultrasonication. Analysis of different tissues and organs of growing plants reveals that a large amount of foreign DNA remains in the cotyledons during the vegetative growth phase, but is redistributed at the flowering stage (when cotyledons etiolate). At this time, the foreign DNA leaves the cotyledons and migrates towards the flowering buds where it accumulates as a highly molecular and double-stranded material. In the F1 progeny, radioactive molecules are found which do not correspond to the endogenous material and which have a density depending on that of the foreign DNA used.

Deterioration of soybean seed in storage

Abstract: Hand harvested Lee 68 soybean seed were rapidly aged to produce six sublots differing in physiological quality. The deterioration of these sublots under moderately adverse storage conditions was then characterized in terms ol the sequence, degree and direction of change in selected physiological parameters. Deterioration was first manifested in an increased sensitivity or susceptibility of the seed to environment stress (accelerated aging, high and low temperatures). Later during the storage period, rate of germination decreased and RQ in creased. Finally, germination percentage, rate of seedling growth, and CL con sumption decreased in that order. In a parallel study, it was demonstrated that permeability of the seed to TTC increased with degree of deterioration, but formazan production decreased when the permeability factor was eliminated. Accelerated aging, cold test, and hot water treatment responses were most closely associated with longevity of the seed in storage. Additional index words: Accelerated aging, cold test, growth rate, longevity, respiration, vigor Introduction Seedsmen usually do not attempt to "carry-over" soybean seed from one plant ing season to the next because of their relatively short storage life. This situation contributes to many problems in the seed industry. It is often a very good practice to "carry-over" 10-20% of the seed of each crop to hedge against a crop failure the following season. More importantly, basic soybean seed stocks (foundation and registered seed) are high priced and sale of these seeds to the oil mill results in a large financial loss as well as loss of valuable seed reserves. One solution to the problem of soybean deterioration in storage would be to select soybean seed lots with high storage potential. Presently, the laboratory germination test is the only widely accepted method for measuring the physio logical quality of seed, and the inadequacies of this test for measuring the per formance of seed lots under various storage environments and less than optimum field conditions have been emphasized by several investigators (6, 8, 10, 15, 19, 26). Deterioration can progress during storage to the extent that the seed are essentially worthless for planting purposes although germination percentage re mains relatively high (16, 20). During the past decade attention has been directed toward investigating the physical (10, 16), physiological (7, 9, 13, 17, 22, 23, 27), and biochemical (1, 2, 3, ijournal Paper No. 2193 of the Mississippi Agricultural and Forestry Experiment Station, State College. Mississippi. -Former Assistant Agronomist, Seed Technology Laboratory, Agronomy Department, MSU, and Agronomist, respectively. 41 This content downloaded from 207.46.13.176 on Mon, 20 Jun 2016 07:30:49 UTC All use subject to http://about.jstor.org/terms 42 I'ROC. ASSOCIATION OF OFFICIAL SEED ANALYSTS 4, 18) changes associated with the process of seed deterioration. Seed deterioration is now believed to be closely related to many of the unsolved seed quality prob lems in the seed industry, such as accurate assessment of the planting value of seed (10, 16, 20, 26), evaluation of the storage potential of the various seed lots of a specific kind (12, 14, 19), determination of the degree of deterioration that seed can sustain without being detrimental to field performance (6, 17, 22, 23, 25), and formulation of a satisfactory definition of seed quality (10, 16, 21, 26). The objectives of the present study were: (1) To study the rate and progress of deterioration in soybean seed under different storage environments; (2) To evaluate different methods for determining the extent and progress of deteriora tion during storage; and (3) To evaluate different methods of predicting seed storability. Materials and Methods Foundation Lee-68 soybean seed of the 1968 crop were hand harvested on the North Agronomy Farm, State College, Mississippi. All seeds were cleaned with hand screens and a laboratory aspirator. Approximately 200 lbs of the seed were adjusted to a seed moisture content of 12.3% in a controlled environment room set at 20°C-90% RH. The seed were then subdivided into eight sublots, sealed in glass containers, and "aged" at 38°C for 0, 5, 10, 15, 20, 25, 28 and 34 days. Seed from the 28 and 34 day aging periods were used only for the dehydrogenase evaluations, while those from the other six aging treatments (periods) were stored at 30°C-50% RH and 20°C 75% RH. Samples were placed in storage at monthly intervals for a period of nine months so that all storage periods terminated on the same date. During the interval from completion of aging treatments to placement in storage, the seed were kept in a refrigerated storeroom at 5°C-40% RH. Non-aged seed served as the "control" in all instances. The extent and progress of deterioration during storage were determined by the following laboratory evaluations: standard germination, first count germina tion, rate of radicle-hypocotyl growth, accelerated aging response, cold test per formance, hot water treatment response, rate of respiration, and dehydrogenase activity. The procedures and methods used for these evaluations are described below. Standard Germination and First Count Germination—Standard procedures as described in the Rules for Testing Seeds (5) were used for laboratory germina tion tests. However, first counts were made four days after planting in an attempt to more accurately identify differences in performance among the samples. Final counts were made eight days after planting. Four replications of 50 seeds each were germinated in rolled paper towels at an alternating temperature of 20-30°C. Radicle-Hypocotyl Length—Ninety seeds from each sample were planted in six replications of 15 seeds each in a straight line about three inches from the top of two moist paper germination towels. A third towel was used as a cover. The towels were then folded, placed on a tray and positioned at a 45° inclination with radicle ends downward in a constant 25°C dark germinator. Root lengths were This content downloaded from 207.46.13.176 on Mon, 20 Jun 2016 07:30:49 UTC All use subject to http://about.jstor.org/terms

Natural Regeneration of Douglas Fir and White Fir on Exposed Sites in the Sierra Nevada of California

Abstract: First- and 2nd-year survival and height growth of natu- rally regenerated white fir and douglas fir seedlings were studied in typical microenvironments on exposed slopes and ridge tops at an eleva- tion of 1300 m in the Sierra Nevada of California. Microsites were described by measuring soil moisture at several depths and potential evaporation at lst-year seedling height. Seedlings survive the summer drought apparently by attaining a type of dormancy in a suitable microsite. Survival was greatest in part shade and in full sun providing squaw carpet (Ceanothus prostratus) mats were present. In these microenvironments soil moisture reaches ten- sions of 15 atm and greater, but the reduced potential evaporation at the seedling tops probably compensates for the lack of soil moisture. The ,growth of natural regeneration is initially quite slow; however, mortality is essentially over by the 2nd year after germination. The' all-age group structure of the mixe'd conifer stands on these sites is apparently related to the occurrence of microenvironments suitable for seedling establish- ment.

Germination and Seedling Response to Temperature, Daylength, and Salinity by Ammophila breviligulata from Michigan and North Carolina

Abstract: Seed germination response to temperature and salinity and seedling response to daylength, temperature, and salinity were studied in Ammophila breviligulata Fern from Michigan and North Carolina Germination results indicated that Michigan seeds required cold treatment prior to germination in a 65-85 F treatment, but that seeds from North Carolina did not require cold treatment and germinated well in either 65-85 F or 65-95 F treatments. During germination, North Carolina seeds were more salt-tolerant and less sensitive to high temperatures than seeds from Michigan Seedling studies revealed that best vegetative growth by both populations occurred under long-day conditions with daytime temperatures between 70 and 80 F Growth of Michigan seedlings was more restricted under short daylengths at lower temperatures and also by high temperatures under both short- and long-day conditions than growth of North Carolina seedlings. Michigan seedlings generally contained more shoot moisture and had higher chlorophyll co...

Influence of strains and rootstocks on photosynthesis, respiration, and morphology of delicious apple trees

Abstract: The performance of young container grown apple trees of two Delicious strains was studied under greenhouse conditions in a 2 year experiment. Redspur Delicious, a spur type strain, and Richared Delicious were grown on seedling rootstocks in the first season and on seedling, MM 106, and M VII-A rootstocks the following year. Net photosynthesis (Pn) of Redspur leaves tended to be higher than the Pn of Richared leaves. One season's data indicated that the Pn leaves of greenhouse grown trees on seedling rootstocks was higher than those on MM 106. Leaves of trees on M VII-A were intermediate in Pn. The respiration rates were not affected by strains or rootstocks. Standard Delicious trees were more vigorous than trees of the spur type as indicated by greater shoot length, internode length, leaf number and total leaf area. The spur type trees had, however, a greater bark-wood ratio. Rootstocks affected both leaf size and dry leaf weight, but strains did not. 4 figures, 2 tables.

Seed size, germination resistance and seedling vigor in barley

Abstract: Marked differences in seedling vigor, as measured by dry weight two weeks after germination, have been demonstrated in F3 lines of a barley (Hordeum vulgare L. emend Lam.) cross between CI 5791 and Ming (CI 4797). These differences can be largely accounted for by differences in seed size, which is itself related to segregation for head type, and by differences in germination resistance. The latter character varies between cultivars and is itself influenced by seed size to some extent. It is concluded that, although seed size, directly and indirectly, can influence seedling vigor, inherent differences in this respect exist between barley cultivars. The significance of this is briefly considered.

A study of some seedling characters and the effects of competition on seedlings in diploid and tetraploid red clover (Trifolium pratense L.)

Abstract: The seed weight of tetraploid red clover was significantly greater than that of diploid in all experiments. Tetraploid seedlings had longer petioles and greater leaf area and accumulated more D.M. than diploid seedlings. The diploid in monoculture populations developed more expanded trifoliate leaves than the tetraploid. Two main effects of competition were:— (a) A significantly lower relative shoot growth rate of the diploid in mixed populations which resulted in significantly reduced D.M. production compared with monoculture populations. Conversely D.M. production in the tetraploid increased significantly in the mixed populations. (b) A significantly greater number of expanded leaves formed by the diploid in monoculture populations compared with the tetraploid was reduced to non-significance in mixed populations. Competition had little or no effect on petiole length or leaf area. The results are discussed in relation to the competitive advantage tetraploid seedlings would have over diploid seed...

Amino acids, soluble proteins, and isoenzyme patterns of peroxidase during the germination of jack pine

Abstract: In germinating jack pine, changes in nitrogenous compounds were separated into two phases, the first, where through imbibition, seeds expanded but the prospective seedling remained enclosed by the ...

Factors affecting acorn production and germination and early growth of seedlings and seedling sprouts

Abstract: Acorn production is extremely variable and unpredictable. Flowering is copious, but many climatic factors influence acorn development from initiation of flowers to acorn maturity. Acorns are consumed by birds, animals, insects, and microorganisms. The establishment of seedlings is more closely related to favorable site factors than to size of crops. A majority of oaks originate from advance reproduction that accumulates under the previous stands during several decades.

The effects of temperature and light energy on dry weight and leaf area changes in seedling plants of Lolium perenne L

Abstract: Nine identical seedling populations of Lolium perenne cv. Grasslands Ruanui were grown at different times in a controlled environment cabinet under 22, 38, and 117 watts m-2Visible radiation (16 hr day length) and at 10, 20, and 30¦C for 32 days. The proportion of the total dry matter present as roots and that of the shoot dry weight present as leaf laminae were only slightly affected by the environment. Shoot growth was dominated by leaf growth; responses to the environment of the average relative growth rate (El,) and the average leaf area growth rate RA) were similar. RW and RA were maximal at 20¦C at each light flux density and increased toward a maximum with increased radiation at each temperature. Maximum RW for seedling plants of L. perenne was about 25% per day. The net assimilation rate increased approximately linearly with increase in light flux and was scarcely affected by temperature. The leaf area ratio was greatly affected by changes in light energy, mainly owing to change in the specific leaf area. The rate of leaf appearance was accelerated by a temperature increase from 10 to 20¦C. Total tiller number was maximal at 20¦C and increased with light flux. When related to leaf number, tillering was reduced only by high temperature at low light energy. The relative changes in net assimilation rate induced by variation in light flux at 20¦C were the same as those in the net photosynthesis of a single leaf lamina. The growth of seedling ryegrass plants in the field in winter is considered to be strongly dependent on temperature and much less restricted by low light energy.

Germination ecology of phacelia dubia var. dubia in tennessee glades

Abstract: A B S T R A C T The ger minationi characteristics of a population of the winter annual Phacelia dutbia (L.) Trel. var. diibia from the middle Tennessee cedar glades were investigated in an attempt to define the factor(s) regulating germination in nature. Factors considcred were changes in physiological response of the seeds (after-ripeniing), temperature, age, light and darkness, and soil moistuire. At seed dispersal (late May to early June), approximately 50 % of the seeds were non-dormaint btit would germinate only at low temperatures (10-15 C). As the seeds aged from June to September, there was an increase in rate and total percent of germination at 10, 1 5, and 20 C, and the maximuim temperature for germination iniereased to 23 C. Little or no germinationi occurred at the Juine, July, and August temperatures in 0- to 2-month-old seeds, even in seeds on soil that was kept continuiously moist duirinig this 3-month period. At the September, October, and November temperattures 3- to 5-month-old seeds germinated to high percentages. In all experiments seeds germinated better at a 14-hr photoperiod than in constant darkness. Inability of 0- to 2-month-old seeds to germinate at high suimmer temperatures allows P. dubia dubia to pass the dry suimmer in the seed stage, while incr ease in optimum and maximuim temper atuires for germination durinig the stimmer permits seeds to germinate in late suimmer and early fall when conditioins are favorable for seedling suirvival and eventual matturation. THE CEDAR GLADES of middle Tennessee are opein, nion-forested areas characterized by bare limestone rock or by shallow, rocky soils, or both. The vegetatioin of these areas consists of lowgrowing anlnual anid perennial herbs that form a sparse and discointinuous cover; therefore, insolation is high at the soil surface, especially during the summer. During late spring and summer the high insolation keeps the shallow soil at or inear permanent wilting percentage much of the time. Even though the glades do receive rains which saturate the soil during the summer, the soil dries to the permanent wilting percentage during a short rainless period. In contrast to the dry summer conditions, the glade soil usually is sufficiently moist in late summer (September) and early fall for seedling establishment and is saturated during much of late fall, winter, and early spring. Mlany plant species of the cedar glade community are drought resistant and, therefore, can carry on the active phases of their life cycles during the dry period. These drought resistant plants include succulents (Opun tia rafitnesquji Engelm., Talinurn calcaricum Ware, and Agave virginica L.) and non-succulents (Croton moniantIogynus Mlichx., C. capitatus \lfichx., Isanthus brachiatus (L.) BSP., Heliotropium teniellum

Advanced sugar–beet seed

Abstract: A technique is described for speeding germination of monogerm sugar-beet seed. The optimum treatment was four cycles of wetting seed with its own weight of water and storing it in a sealed container for 24 hours before drying for 48 hours. The number of cells per embryo was doubled, seedlings emerged approximately 2·5 days sooner and seedling shoot weight was increased by 31 to 53%.

Variation in photosynthetic activity in cereals and its implications in a plant breeding programme I. Variation in seedling leaves and flag leaves

Abstract: The extent of variation in photosynthetic activity in the seedling and flag leaves of fourteen oat varieties, and in the seedling leaves of three varieties each of wheat and barley has been investigated. The suitability of NaH14CO3 and Warburg manometric techniques for handling the attribute of photosynthetic efficiency in a plant breeding programme is assessed. Results obtained are considered in comparison with estimates of net assimilation rate (E), relative growth rate (R) and leaf area ratio (F) derived from growth analysis data. The relationships with yield and implications for a plant improvement programme are discussed.

Morphogenic studies in tissue cultures of the parasiteSantalum album L.

Abstract: Whole seeds, excised embryos, and excised endosperm ofSantalum album were aseptically cultured with a view to studying seed germination in isolation from the host species, and to establishing callus cultures from both embryo and endosperm for comparative studies et their morphogenesis. Seed germination and seedling formation occurred normally only on modified White's medium supplemented with casein hydrolysate or coconut milk, or with both substances. Neither the excised embryo nor the endosperm grew on any of the culture media tested. However in about 17 per cent seed cultures on White's medium supplemented with 2,4-D, kinetin, and yeast extract, the endosperm degenerated, whereas the embryo callused and subsequently differentiated into innumerable embryoids; eventually the embryoids developed into normal plantlets. Callusing of the endosperm occurred also in seed cultures on four media supplemented variously with 2,4-D, kinetin, and yeast extract. Although the endosperm tissue grew through several passages no organ fornation was observed.

Effects of relative humidity and type of container on the growth of f1 hybrid annuals in controlled environments

Abstract: The effects of three levels of relative humidity (40 %, 65 %, and 90 %) and two types of containers (clay and plastic) on the seedling growth of three F, hybrid annuals were determined after 14 days of controlled-environment treatment. Forty percent relative humidity was severely limiting to the seedling growth of 'Blue Blazer' ageratum (Ageratum houstonianum Mill.), 'Pink Cascade' petunia (Petunia hybrida Vilm.), and 'Double Eagle' marigold (Tagetes erecta L.). Raising the relative humidity to 65 % resulted in striking increases in fresh weight, dry weight, and leaf area, especially when clay containers were used. Height of the main shoot was increased significantly at 65 % relative humidity but node number was influenced only slightly. Increasing the relative humidity further to 90 % had no significant effect on fresh weight, dry weight, or percent dry weight for any of the three species, in either container. Leaf area was increased significantly at 90 % only in ageratum seedlings grown in clay pots. Each species responded differently to the type of container used. The fresh weight and dry weight of petunia seedlings were significantly greater in plastic pots at every level of humidity while those of marigold seedlings were unaffected by the type of container used. Ageratum seedlings, on the other hand, had significantly greater fresh weights and dry weights in clay pots only at 90 % relative humidity. THE IMPORTANCE OF relative humidity in controlled-environment studies on plant growth and development is often not realized, although careful attention is generally paid to other environmental factors, such as temperature, light intensity, and photoperiod. Went (1957) has indicated that plants grow best when the relative humidity of the air is somewhere in the range of 50-88 %. But precise information is lacking on the level of atmospheric moisture required for optimum plant growth (Wangermann, 1961). Some information on the effects of relative humidity is available for crops such as tomatoes (Went, 1944), peanuts (Fortanier, 1957), strawberries (Went, 1957; Pareek, Sivanayagam, and Heydecker, 1969), coffee (Went, 1957), several grasses (Went, 1957), kale, sugar beet, and spring wheat (Watson, 1964), barley (Natr and Kousalova, 1965), wild white clover, dwarf bean, broad bean, peas, cucumber, sweet pepper, cauliflower, kohlrabi, turnip, radish, beet, raspberries (Pareek et al., 1969), or experimental plants such as sunflower (Demidenko and Golle, 1939; Pareek et al., 1969) and Mimosa (Wallace, 1931; Went, 1957). 1 Received for publication 7 January 1971. The authors are indebted to E. J. Koch, Biometrician, Division of Biometrical Services, Agricultural Research Service, U. S. Department of Agriculture, Be tsville, Maryland, for assistance with the statistical analysis of the data, and to George J. Ball Inc., West Chicago, Ill., for kindly furnishing the seed. Preliminary studies conducted in the Phy toEngineering Laboratory with selected F1 hybrid annuals indicated that relative humidity may be of considerable importance in influencing seedling growth of these plants. The present study was, therefore, conducted to determine the effects of three levels of relative humidity (40 %, 65 %, and 90 %) on the growth and development of selected F1 hybrid annuals under controlled-environment conditions. Since a previous experiment had shown a striking influence of containers on seedling growth under controlled environments, the possible interactions of relative humidity and containers were also examined. This report is one of a series of single-factor and multiple-factor studies on optimum environments for seedling growth of selected F1 hybrid annuals. MATERIALS AND METHODS Plant materialPlant material consisted of three F1 hybrid annuals-'Blue Blazer' ageratum (Ageratum houstonianum M\lill.), a day-neutral plant; 'Pink Cascade' petunia (Petunia hybrida Vilm.), a long-day plant; and 'Double Eagle' marigold (Tagetes erecta L.), a short-day plant. These cultivars were chosen because: (1) they are widely used as bedding plants; (2) they exhibit the major types of photoperiodic responses; and (3) they were previously found responsive to controlled-environment treatment (Cathey, 1967). Seed were planted in 7.5-cm plastic and clay pots containing a synthetic soil mix of peat and

Seedling grower and method of planting seedling cultivated in the seedling grower

Abstract: A seedling grower and a method of planting seedling cultivated in the seedling grower are disclosed. Said seedling grower is characterized by comprising a plurality of cells arranged in lattice form and formed by adhesively bonding together wall members made of a material such as paper, being collapsible when not in use and being able to be stretched into a spread lattice form from the collapsed state. Each of said cells is adapted to contain earth and cultivate a seedling therein.

Germination and Herbicide Susceptibility of Six Pigweed Species

Abstract: The germination and growth of six pigweeds (Amaranthus spp.) were studied in the germinator and greenhouse. Treatments with sulfuric acid, acetone, sodium hypochlorate, and potassium nitrate variously influenced species germination. Seedlings emerged more rapidly at 100 F than at other soil temperatures. Variation in seedling characteristics was noted. Some species were more susceptible to 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) and 2,4-bis (isopropylamino)-6-(methylthio)-s-triazine (prometryne) than others in the greenhouse. In the field little variation in susceptibility to several preplant and preemergence herbicides was found; but there were differences when postemergence herbicides were used.

Effect of Temperature and Light Intensity Early in Ontogeny on Growth of Pinusresinosa Seedlings

Abstract: Low temperature or low light intensity following germination of Pinusresinosa seeds greatly suppressed subsequent seedling development, with cotyledon expansion inhibited more than root expansion. ...

A study of seed lots of peas (Pisum sativum L.) differing in predisposition to pre-emergence mortality in soil

Abstract: SUMMARY In three seed lots the condition of the cotyledons was found to be important in denning seeds predisposed to pre-emergence mortality. Such seeds readily exuded materials into seed-steep water, were rapidly infected by Pythium spp. and showed intensely stained cotyledons after being in solutions of tetrazolium chloride. In soil, infection of the cotyledons was found to occur before infection of the seedling axis and occurred in normal seed if disks of cotyledon material were placed in the soil next to the seed. It is suggested that cotyledons influence predisposition by either increasing exudation around the seed and stimulating the fungal pathogen or by acting as a food base for the fungal hyphae which infect and kill the seedling axis.

Effect of Bipolaris sorokiniana on germination and seedling survival of varieties or lines of 14 Triticum species

Abstract: Seedlings of Triticum species and varieties differed markedly in reaction to inoculation with Bipolaris sorokiniana in laboratory tests. There appeared to be no consistent relationship between seedling reaction and previously established field disease ratings. The field-resistant line 680 of T. aestivum, in particular, was very susceptible in the seedling stage. There appeared to be no definite relationship between disease reaction and different genomic groups although resistance tended to increase with the ploidy level.There was some direct relationship between wheat seedling survival after inoculation and sensitivity to culture filtrates of B. sorokiniana. However, Conquest barley showed a high degree of seedling resistance to inoculation but was very sensitive to culture filtrates. Seedling survival was not related to speed of germination. Isolates of B. sorokiniana varied in degree of aggressiveness towards seedlings but this did not appear to be correlated with toxin production.