Showing papers on "Seedling published in 1970"

Some factors influencing the germination and early seedling development of pasture plants.

Abstract: Some of the important environmental and plant factors influencing the germination and early seedling development of a number of temperate grasses and legumes have been investigated under controlled conditions. Significant differences were found between legumes and grasses in a number of characters which appear to be important for establishment under field conditions, including quantitative aspects of water absorption, rates of germination, and early root elongation. Ryegrass was superior to all other species in its ability to germinate under conditions of moisture stress. The lower limit for germination was from 4 to 6 bars below the limiting potential found for the other species, and thus may be one of the important factors contributing to the ease of establishment of this species in the field. The early onset of autotrophic growth in young seedlings, as judged by the utilization of external nutrients and the attainment of positive net photosynthesis, occurs within 5 days of imbibition under favourable conditions, well before the exhaustion of endogenous reserves. This highlights the need for adequate water, nutrients, and light during this early stage of seedling development. It also suggests that reserves available to the seedling are probably in excess of requirements under favourable conditions, and may be of potential value under adverse conditions. These results are discussed in relation to the definition of field problems, and to some likely breeding objectives to improve establishment.

Some factors influencing the germination and early seedling development of pasture plants

Abstract: Some of the important environmental and plant factors influencing the germination and early seedling development of a number of temperate grasses and legumes have been investigated under controlled conditions. Significant differences were found between legumes and grasses in a number of characters which appear to be important for establishment under field conditions, including quantitative aspects of water absorption, rates of germination, and early root elongation. Ryegrass was superior to all other species in its ability to germinate under conditions of moisture stress. The lower limit for germination was from 4 to 6 bars below the limiting potential found for the other species, and thus may be one of the important factors contributing to the ease of establishment of this species in the field. The early onset of autotrophic growth in young seedlings, as judged by the utilization of external nutrients and the attainment of positive net photosynthesis, occurs within 5 days of imbibition under favourable conditions, well before the exhaustion of endogenous reserves. This highlights the need for adequate water, nutrients, and light during this early stage of seedling development. It also suggests that reserves available to the seedling are probably in excess of requirements under favourable conditions, and may be of potential value under adverse conditions. These results are discussed in relation to the definition of field problems, and to some likely breeding objectives to improve establishment.

Mycorrhizal Responses of Radiata Pine in Experiments with Different Fungi

Abstract: SUMMARY In glasshouse and field studies large differences occurred between different mycorrhizal fungi in their stimulation of radiata pine (Pinns radiata D.Don) growth. In the glasshouse, significant differences in this also occurred between strains of Rhizopogon luteolus Fr. and Nordh. R. luteolus and Suillus granulatus (L. ex Fr.) O. Kuntze usually gave good stimulation but S. Intens (L. ex Fr.) S. F. Gray was usually poor. Field responses to inoculation were obtained within 200 m of an existing plantation of radiata pine at a site where naturally occurring mycorrhizal fungi were present. Growth rates of inoculated plants were greater than those of uninoculated plants for the first 32 months after which growth rates were the same, height differences at that time being maintained. When growth rates of inoculated and uninoculated trees became the same all plants in uninoculated plots were dark green and had become mycorrhizal. Increased seedling survival during the dry summer following planting occurred ...

A Comparative Study of Cotyledons as Assimilatory Organs

Abstract: Cotyledons of 11 species were studied at a number of stages of germination. The hypogeal pea and runner bean cotyledons did not expand, lost weight, and survived for a relatively short time only. They also produced little chlorophyll on exposure to light, possessed no stomata, and had a very low capacity for 14C02 fixation. The epigeal french bean had cotyledons that were basically of the hypogeal type. Although both white and blue lupin cotyledons showed a pro gressive weight loss, they underwent limited expansion and were more persistent than either pea or bean. They also produced considerable amounts of chlorophyll, had stomata on both upper and lower surfaces, and fixed restricted quantities of 14C02. The cotyledons of the other epigeal species studied showed varying degrees of expansion, up to almost fifty-fold in cucumber, and generally maintained or increased in total dry weight for at least a restricted period. Stomata occurred on both upper and lower surfaces, extensive chlorophyll production took place, and 14COa fixation values were high. Expansion was determined by increase in cell size, and not in cell number except in the case of cucumber where both factors were involved. In species where cotyledon cells were large initially little or no expansion occurred, whereas initial cell size was small in cotyledons which expanded to a large extent. Epigeal cotyledons with a high expansion factor possessed other characteristics which made them adapted for photosynthesis, whereas epigeal species with lower cotyledon expansion together with hypogeal species were less well adapted. This was not unexpected in the case of pea and runner bean, but led to the conclusion that french bean cotyledons are ' accidentally epigeal' in that they showed virtually no adaptation to an aerial existence. The different capacities of the cotyledons studied suggests that they have differing roles in the control of seedling growth.

Metabolic changes of polyamines during the germination of phaseolus vulgaris

Abstract: SUMMARY The distribution and changes in spermine and spermidine during the germination and seedling growth of bean (Phaseolus vulgaris) were investigated. The results show in vivo a substantial parallelism between RNA and protein changes and polyamine changes during germination. Spermine and spermidine diminish in the cotyledons and increase in the shoots especially the epicotyls. The data concerning in vitro cultures of isolated cotyledons and embryos show that there is a dc novo synthesis of spermine and spermidine in the seedlings particularly in the light. Although the greater part of the polyamines are translocated from cotyledons to embryo and afterwards into the different parts of the growing seedling, some is degraded. It is concluded that synthesis and translocation of such compounds during germination can be compared with an analogous pattern of RNA and protein changes.

Phosphorus uptake from soils by corn hybrids selected for high and low phosphorus accumulation.

Abstract: Field, greenhouse, and laboratory experiments were conducted over a period of 4 years to relate P accumulations in ear leaves of different corn hybrids and other plant responses to addition of P to soils and root morphology, including the length of the radicle, diameter of the radicle, and the number of seminal roots produced after 4 days in an incubator of high relative humidity at 28 C. In addition, experiments were conducted to determine the relationship of P accumulation in ear leaves and grain yields to P concentrations in seedling plants, seedling growth rate and P uptake from a zone 25 an (10 inches) below the soil surface. It was concluded that the concentration of P in seedling plants can be used to predict the availability of P in the soil. The concentrations of P accumulated in ear leaves by the different hybrids could not be explained on the basis of the P-absorption characteristics of their roots, but inherent differences among hybrids with respect to depth of rooting was suggested.

Seed prédation and dormancy in the population dynamics of Avena fatua and A. barbata.

Abstract: Estimates of seed loss due to animal predation in Avena fatua and A. barbata over a number of sites in the California annual—type grasslands varied from 0% to 65% of the total seed load. Avena species showed complex patterns of variation in germination both between and within populations. Counts of seedling deaths due to precocious germination in nature suggest that the observed variation in germination provides insurance against seedling losses due to somewhat erratic fall rains. These factors are significant in regulation of Avena populations. See full-text article at JSTOR

Physiological and chemical features of magnetically treated winter wheat seeds and resultant seedlings

Abstract: Seed of winter wheat (Triticum aestivum L.), cultivar Kharkov 22 MC, magnetically treated before germination respired more slowly, released less heat energy, and grew faster during the initial 16 hr than similar but untreated seed. Magnetically treated seed absorbed more moisture and contained more reducing sugar during the initial 72 hr of growth than un-treated seed. Addition of oxygen to the seed environment during germination repressed shoot growth and enhanced root growth of magnetically treated wheat but had no effect on untreated seed. Addition of carbon dioxide to the seedling environment suppressed the growth of shoots and roots of treated and untreated wheat seed equally.

Lime‐chlorosis as a factor in seedling establishment on calcareous soils

Abstract: SUMMARY The water relations of a number of species affected by lime-chlorosis have been studied by following the development of leaf water deficits in detached leaves gravimetrically. It has been found, both for material collected in the field and for material raised under controlled laboratory conditions, that chlorotic leaves invariably lose water more rapidly than do green leaves of the same species. The rate of transpirational loss of individuals of a species is directly related to the degree of chlorosis they exhibit. Addition of iron chelate to soil in which a chlorosis-susceptible plant grows alleviates the chlorosis and the rate of transpiration is also greatly reduced. The age of the material and intrinsic soil factors also influence rates and patterns of transpirational loss. Both the stomatal and cuticular phases of transpiration appear to be affected in chlorotic material, where the larger leaf water deficits may be due either to more rapid loss during the stomatal phase, coupled with later stomatal closure, or to more rapid cuticular loss, or both. The percentage of dry matter in chlorotic leaves is reduced compared with that in green leaves. The ecological significance of the overall findings is discussed in relation to the potential survival of species invading calcareous soils as seedlings. Such seedlings are very often subjected to annual droughts.

Ammonium and Salt Inhibition of Some Physiological Processes Associated with Seed Germination

Abstract: Seed germination was totally inhibited by high (0.1 N) concentrations of potassium or ammonium salts. Partial inhibition of germination occurred with low (< 0.01 N) concentrations of ammonium salts, but low concentrations of potassium salts did not affect germination. Except with extreme salt or ammonium injury, the inhibition of germination was at least partially reversible. Respiration of germinating seeds was inhibited by both species of salts. Seedling development was severely impaired by ammonium salts, but not by potassium salts.

Seed characteristics and seedling emergence of Dalmatian toadflax.

Abstract: In eastern Washington Dalmatian toadflax (Linaria dalmatica (L.) Mill) produces seeds for about 3 months, beginning in early July, with over 95% produced during the first 5 weeks. A large plant will produce a half million seeds under good conditions. Seeds are sharply angular, slightly winged, and 1 to 2 mm long. Approximately 7,000 weigh 1 g. Seeds are spread by wind and browsing animals. Some seeds will germinate under laboratory conditions the same season in which produced, but germination from dry storage increases for 2 to 3 years, with a periodic low in November and a high in April. Over 90% germination is obtained with 2 to 3-year-old seeds in the laboratory. Germination in the field occurs in both spring and fall, and seedlings can emerge from a soil depth of 2 to 2.5 cm.

Sunflower date of planting and chemical composition at various growth stages.

Abstract: Six sunflower (L.) varieties were planted at seven dates ranging from April 24 to June 28,1967 through 1969. Early May plantings produced highest seed yields, hectoliter weights, oil percentages, and large seed percentages. Days from planting to emergence and emergence to flowering decreased from early to late planting dates. Date of planting was the variable which most consistently affected seed yield. It overshadowed both varieties variation and the interaction of dates ✕ varieties.Whole plant samples for N, S, P, K, Ca, Mg, Fe, Na, Sr, Zn, Cu, Mo, Mn, and B analyses were taken at 13 different growth stages and separated into root, stem-leaves-receptacle, and seed. Comparative data for seedling, heaaing, flowering, and maturing periods of growth showed concentrations of most elements declined with age in stems- leaves-receptacle.Variation in composition of stem-leaves-receptacle among growth stages was greater than among varieties, but this relationship was reversed in seed. Seed; stemleaves-receptacle, and root differed in composition and in relative rank of the elements

Studies on seed pelleting as an aid to legume seed inoculation. 2. Survival of Rhizobium meliloti applied to medic seed sown into dry soil

Abstract: Seed of Medicago truncatula and Medicago littoralis, with and without lime pelleting and inoculation, was sown dry into medic-free, Rhizobim meliloti-free soils at 12 sites in the Western Division of New South Wales. At the different sites, periods between 1 and 88 days elapsed before germinating rain fell. Seedling nodulation was used as the index of inoculant survival. Nodulation was variable, but the variation was independent of the time between sowing and germination. Best nodulation occurred in treatments in which peat inoculant was incorporated within a lime pellet around the seed. These treatments were superior to others where broth inoculant was incorporated in the pellet or where peat inoculant was applied externally to pelleted or unpelleted seed. Nodulation was improved by incorporating an increased level of peat inoculant in the pellet. In storage, a very low survival rate was recorded in all treatments except those incorporating peat inoculant within the pellet. The results are discussed in relation to the practicalities of pre-inoculation techniques and of sowing inoculated medic seed into dry seed beds.

Genecological aspects of flowering and vegetative reproduction in Rumex acetosella L.

Abstract: Summary Records of time of flowering obtained from herbarium specimens of Rumex acetosella L. indicated seasonal delays and a shorter period of flowering with increasing latitude and altitude, while earlier flowering was indicated in regions of Mediterranean climate. Observations on the time of flowering in a uniform environment of populations spanning 50° of latitude showed correlations with latitude, and deviations from this trend could be attributed to adaptation to montane, continental, or Mediterranean climates. Experiments showed that the species required long days for floral induction in the seedling year, the populations varying in the length of day required, with populations from high latitudes not flowering in the prevailing daylengths at Christchurch (43° 30′S). In the second year of growth all populations flowered in the prevailing daylength at Christchurch, although long days and high temperatures hastened the maturation of flowers and the populations varied in time of flowering. Population d...

Seedling growth in four species of chionochloa (gramineae)

Abstract: Summary Seedling growth in Chionochloa macra, C. rigida, C. rubra, and C. flavescens was measured by leaf production, tillering, and yield of leaves and roots. Each species was raised in its own soil and that of the others, both with and without added nitrogen and phosphorus. Seedlings of all species responded to fertiliser, especially to phosphate. Some characteristic growth patterns emerged, particularly that of C. macra which produced consistently shorter leaves, low leaf and root yield, but high tillering compared with other species. Soils strongly influenced growth in all species and the species themselves proved adequate assessors of differences among soils. C. rubra and C. rigida seem to be more tolerant of a wider range of soils than C. macra and C. flavescens.

The light promoted germination of the seeds of chenopodium album l. iv. effects of red, far-red and white light on non-photoblastic seeds incubated in mannitol

Abstract: SUMMARY The effects of red, far-red and white fluorescent light on the germination of dark germinating seeds of Chenopodium album, incubated in a range of mannitol concentrations, have shown that the far-red absorbing form of phytochrome (Pfr) is present in these seeds. The requirement of the germination processes for Pfr increased, when the osmotic concentration of the incubation medium was increased. It is concluded that this requirement for Pfr depends on the position of a balance between promotive and inhibitory factors. Pfr influences this balance in a positive direction. It was shown that osmotic stress, a thick seed-coat and (RS)-abscisic acid can function as inhibitory factors. In its influence on the last stage of the visible germination phenomena (the protrusion through the inner seed-coat layer) white light resembles in lower osmotic concentrations red light, in higher concentrations it resembles far-red light. The earlier stages (elongation inside the seed) are influenced, in all tested concentrations, similar by red and white light. It is assumed that during the last phase of the germination process “seedling phytochrome” instead of “seed phytochrome” has a regulatory function.

Effects of temperature and photoperiod on growth and reproductive development in Hyparrhenia hirta.

Abstract: Hyparrhenia hirta occurs naturally in the Mediterranean region and in the winter rainfall areas of South Africa, in association with temperate festucoid grasses. However, the temperature response curves, flowering behaviour, and widespread apomixis found in this species are more typical of other tropical members of the Andropogoneae. This residual tropical adaptation provides an explanation for the sensitivity of H. hirta to low temperature (below 15¦C) during seed germination, and especially during the seedling stage, which makes autumn establishment difficult in temperate climates. Also, the low seed yield is attributable to the high proportion (c. 50%) of male florets in the inflorescence, and the breakdown of both sexual and apomictic embryo sacs during development. A possible genetic approach to the improvement of both these characters, utilizing facultative apomixis, is discussed.

Distribution of phenylalanine ammonia-lyase in etiolated and far-red irradiated radish seedlings.

Abstract: In dark-grown Raphanus seedlings, most of the PAL activity is found in roots where it increases sigmoidally during organ development. In hypocotyls, the dark increase of enzyme activity is linear with time. In cotyledons and hooks, dark activity is very low and remains constant. After onset of continuous far-red irradiation, an activity increase is observed in all parts of the seedling. In cotyledons and hooks, the increase is followed by a decrease. This is comparable to light-induced PAL activity described in other materials. In roots and hypocotyls, the initial increase is not followed by a decrease. In dark-grown roots and hypocotyls PAL activity is correlated to fresh weight augmentation. In no part of the seedling could a correlation be found between light-induced PAL activity and anthocyanin formation.

Promotion of pistillate flowering in Cucúrbita by 2-chloroethylphosphonic acid.

Abstract: All accessions tested of four cultivated species ofCucurbita responded to seedling treatment with 250 ppm 2-chloroethylphosphonic acid by developing only pistillate flowers for an extended period. This growth regulator is a promising means of facilitating hybrid seed production of squash. A similar treatment did not induce flowering of wild species ofCucurbita that were vegetative under the environmental conditions of the experiment.

Autecological studies of Psoralea subacaulis.

Abstract: Psoralea subacaulis T & G (Leguminosae) is an acaulescent, herbaceous perennial endemic to the cedar glades of middle Tennessee, northern Georgia, and northern Alabama It is a spring aspect dominant of the open, well-lighted portions of gravelly cedar glades In late June or early July, the entire shoot dies back At the top of the tuberous root, about 5 cm below the surface of the ground, there is a small undifferentiated bud that gives rise to next season's growth During the hot, dry summer months this bud elongates very little; but with the onset of cooler and wetter weather in the autumn it begins to elongate and the shoot apex shifts from vegetative to floral Shoot elongation and apex development continue during the winter and by the following spring the shoot, with its apex in an advanced stage of development, emerges from the ground After meiosis and pollen grain formation in March and early April, the shoot expands rapidly and the reproductive portion of the life cycle is completed before summer Seeds are shed in late May and lie dormant until at least the following March or April, at which time germination and seedling establishment occur Plants do not reproduce until they are 5 to 6 years old Seed dormancy results from two distinct factors: (1) a "hard" seed coat impermeable to water, and (2) one or more water-soluble chemical inhibitors In order for maximum germination to occur in a minimum time, seeds require both scarification and leaching Bud expansion and flowering in P subacaulis are controlled by the annual thermoperiod In plants which had just become dormant, a 2to 3-month warm period followed by a 3-month cold treatment initiated normal growth and development Plants given a 3-month cold treatment not preceded by a warm treatment developed abnormally and did not flower Adaptations of P subacaulis to its cedar glade environment include: (1) capacity to complete the most active part of its life cycle during the cool moist season and to remain dormant during the hot, dry summer; (2) delay of germination until spring when moisture and temperature are favorable for seedling establishment; (3) capacity to complete reproductive stages of its life cycle quickly, and (4) capacity to become established in the rocky substrate, where larger plants find establishment difficult

The physiology of growth in Subterranean clover. I. Seedling growth and the pattern of growth at the shoot apex

Abstract: The shoot apex of Trifolium subterraneum L. is spirodistichous, with a divergence angle of 160° and a phyllotaxis index of 2. The vegetative plant is defined quantitatively in terms of lengths of successive leaves, leaf areas, and dry weights of the leaves and all major plant parts for a 29-day growth period. The selected environment gave very high values of net assimilation rate (3 .0 mg cm-2 day-1for early growth). The properties of the shoot apical system are further defined in terms of volumes of meristematic and very young parts. The picture is extended by linking it with fresh weight data for the leaves. To a remarkable extent the data, transformed to logarithms, can be accounted for by arrays of linear regressions on time, the members of which show decreasing slopes with increasing leaf number. However, the most instructive description is obtained from an array of relative growth rate curves for successive leaves. While the existence of one general pattern of leaf growth seems unlikely, there is evidence for a marked increase in relative growth rate during leaf initiation. Exponential growth in length seems to be fairly common in young leaf primordia, but exponential growth in volume occurs in a variety of patterns in different plants. Attempts to link these occurrences with events in vascular differentiation and thus with the supply of substrate for growth have not been successful. It is suggested that properties of the system as a whole may be relevant.

Studies on seed pelleting as an aid to legume seed inoculation. 3. Survival of rhizobium applied to seed sown into hot, dry soil.

Abstract: Seed of four legume species with various forms of lime pelleting and inoculation was sown into hot, dry soil at Katherine, Northern Territory, where it lay dormant for 7-9 weeks before germination commenced. Seedling nodulation was used as the index of inoculant survival. Where the seed was sown at a shallow depth, Rhizobium survival was poorer than on seed sown more deeply; this was attributed to the higher temperatures near the soil surface. Rhizobia survived best in those treatments in which peat inoculant was incorporated within the pellet. Rhizobium meliloti applied to Medicago sativa seed showed a high degree of tolerance of the conditions and seedling nodulation exceeded 90 per cent in several instances. Nodulation of Trifolium pratense and T. rueppellianum never exceeded 50 per cent and little nodulation occurred with Lotus pedunculatus. It is concluded that lime-pelleted Medicago seed with peat inoculant incorporated within the pellet can be sown into hot, dry soil with a strong expectation that the inoculant will survive and the seedlings nodulate.