GERMINATION AND SEEDLING RESPONSE OF ATLANTIC AND GULF COASTS POPULATIONS OF SPARTINA ALTERNIFLORA

Germination response to thermoperiod and seedling response to photoperiod-thermoperiod treatments and to uniform field conditions were compared for 12 populations of Spartina alterniflora Loisel. from along the Atlantic and Gulf coasts. Germination above 50 % was attained by seeds from all populations in 25–10, 30–15, and 35–20 C alternating diurnal thermoperiods following three months storage in estuarine water at 2–3 C. Except for Massachusetts, Connecticut, and Virginia, seedlings of populations from Ocracoke Island, North Carolina, and northward produced significantly more total biomass in the long- than in the short-day photoperiod in the 30–26 C thermoperiod. Seedling biomass of populations southward of Ocracoke Island, North Carolina, was not significantly affected by photoperiod in either the 18–14 or 30–26 C thermoperiods. Seedlings of all populations from Georgia and northward were significantly shorter and produced significantly more culms in the short- than in the long-day photoperiod in the 30–26 C thermoperiod. Seedlings from Mississippi and all populations from Virginia and northward had significantly lower shoot to root plus rhizome ratios under the short- than the long-day photoperiod in the 30–26 C thermoperiod. Flowering occurred only in populations from Ocracoke Island, North Carolina, northward in the 30–26 C thermoperiod. In a field study, flowering occurred in a north to south sequence and in all populations by the end of the second growing season. Controlled environment and field seedling studies indicated that southern populations flowered later, exhibited longer growing periods, and were less sensitive to photoperiod than northern populations. New England, Mid-Atlantic, South Atlantic, and Gulf coast populations differed in height, color, flowering time, length of growing period, and morphology through two growing seasons in the field study.     

GERMINATION AND SEEDLING EMERGENCE IN SPERGULA ARVENSIS

Spergula arvensis L. (Caryophyllaceae) is a cosmopolitan weedy annual that exhibits a genetically based seed coat polymorphism in which two primary seed types, papillate (P) and nonpapillate (NP), are produced. This study examined germination response of the two morphs and seedling emergence in Pacific coast populations. Germination behavior was complex and variable among populations and between seed morphs. Seeds from some populations exhibited greater temperature sensitivity and/or differentiation between morphs. Freshly produced seeds from grassland and ruderal populations were strongly dormant at the time of dispersal, in contrast to seeds from cultivated or summer-wet populations. In San Francisco Bay area populations, germination and seedling emergence was largely simultaneous, following the first substantial fall rains.     

GERMINATION AND SEEDLING DEVELOPMENT OF SOYBEANS IN A CARBON DIOXIDE-DEFICIENT ATMOSPHERE

During the initial phase of germination and seedling development of soybeans, most of the increase in dry weight in the embryo axis occurred in the hypocotyl. The epicotyl did not undergo a rapid increase in size and dry weight until the 4th to 5th day of growth. From day 1 to 11 dry weights of the hypocotyls in the “CO₂-normal” and “CO₂-Iimiting” (less than 50 ppm [0.005%] atmospheric CO₂) treatments were similar. By day 13 the CO₂-normal hypocotyls had continued their rapid increase in dry weight while the dry weight of the hypocotyls grown under CO₂-limiting conditions had decreased. The parallel decrease in dry weight of the cotyledons that occurred for both CO₂ treatments (days 1 to 13) suggested that CO₂ content of the atmosphere is not a controlling factor in the digestion or hydrolysis of food reserves in the cotyledon during germination and seedling development. This is supported by the failure of the CO₂ treatments to produce significantly different patterns in utilization of lipids, total carbohydrates, or proteins in the cotyledons. The seedlings grown under either the limiting or normal CO₂ atmospheres utilized their cotyledonary carbohydrates and lipids before the proteins. Sufficient food reserves are present in the soybean cotyledon storage cells for seedling development until about day 9. Net CO₂ uptake by soybeans in a CO₂-normal environment first occurred between days 9 to 11.     

花生种子的磁处理对其萌发及幼苗生长的影响

本试验着重研究了用交、直流磁场对花生种子进行处理后,在种子萌发及幼苗生长过程中产生的影响。结果表明,一定强度的交流或直流磁场对种子的萌发及幼苗生长有一定的促进作用。处理过的种子存放一年后,磁场对种子萌发的作用依然存在。     

不同浓度MNP与水稻种子萌发和幼苗生长间的相关性研究

MNP（2-methoxy-5-nitro-phenal的钠盐)是一种植物生长调节剂,它是笔者参照类似物的合成原理和方法研制而成。本文研究了MNP对水稻种子萌发和幼苗生长的作用,从而为合成物MNP在农业上的应用。提供了科学依据。     

FIELD GERMINATION AND SEEDLING GROWTH OF CH AND CL PROGENY OF IMPATIENS CAPENSIS (BALSAMINACEAE)

The germination behavior and early growth of chasmogamous (CH) and cleistogamous (CL) progeny of Impatiens capensis were investigated in two eastern Nebraska stands. Field germination of families of buried seeds was scored in mid-April. In one stand a significantly higher proportion of CL seeds germinated than CH seeds while no significant differences were observed in the second stand. Among-family variation in germination rates was significant in both stands. The time course of field germination was similar for CL and CH seeds. A sample of the germinated CL and CH seedlings, matched in size, was planted individually in pots and grown in the greenhouse for five wk. Early growth of CL and CH seedlings was similar. In addition, CL seedlings were as variable as CH seedlings for four morphological traits. Overall, a large fitness advantage for CH progeny was not detected in the germination and early growth of Impatiens capensis seedlings.     

EFFECTS OF BURIAL BY SAND ON SEED GERMINATION AND SEEDLING EMERGENCE OF FOUR DUNE SPECIES

On the beach strand, seedlings of Cakile edentula, Elymus canadensis, and Corispermum hyssopifolium emerged from mean depths of 3.4, 3.5 and 3.0 cm, respectively. The frequency distribution of the depth of seedling emergence was 1) significantly leptokurtic for C. edentula and slightly platykurtic (not significant) for C. hyssopifolium and E. canadensis, and 2) significantly skewed to the right for C. edentula and E. canadensis but not for C. hyssopifolium. The total germination was not influenced by the burial of seeds at 2, 4, 6, 8, 10 and 12 cm depths except in Ammophila breviligulata in which the germination decreased with increasing depth of burial. The rate of emergence and total emergence decreased with increased sowing depth for all four plant species. Species with larger seeds emerged from deeper burial treatments than those with small seeds. The order of ED₅₀ (the planting depth from which 50% of the seedlings emerged) and ED_max (the maximum depth from which a seedling emerged) was C. edentula (upper seeds) > E. canadensis > C. edentula (lower seeds) ≖ C. hyssopifolium > A. breviligulata and it coincided with weight per seed.     

GERMINATION AND GROWTH OF BIRD-DISPERSED PLANTS: EFFECTS OF SEED SIZE AND LIGHT ON SEEDLING VIGOR AND BIOMASS ALLOCATION

I examined germination and seedling growth in nine species of fleshy-fruited plants from Washington and Idaho to assess their relative responses to sun and shade. I allowed seeds to germinate over a period of 500 days, and grew the seedlings in a greenhouse for 35 days prior to harvest. Cumulative percentage germination of six species approximated logistic curves. Species with larger seeds were more shade-tolerant, which resulted largely from greater biomass allocation to roots by these species. Seedlings of Rosa gymnocarpa, Sorbus scopulina, Symphoricarpos albus, Clintonia uniflora, and Streptopus amplexifolius grew larger in open sun than in shade (35% open sun), whereas those of Actaea rubra, Disporum trachycarpum, Smilacina racemosa, and Smilacina stellata showed no differences. Percentage root biomass was higher in sun than in shade for R. gymnocarpa, S. scopulina, S. albus, C. uniflora, and S. amplexifolius, but lower for S. stellata. In C. uniflora, S. racemosa, and S. stellata, seeds from unripe fruits failed to germinate. The results suggest that light gaps resulting from periodic disturbance of canopy influence recruitment of bird-dispersed species differentially and thereby contribute to maintaining high species richness and diversity in understories of temperate coniferous forests.     

MORPHOMETRIC VARIABILITY IN CONTINENTAL AND ATLANTIC ISLAND POPULATIONS OF CHAFFINCHES (FRINGILLA COELEBS)

The magnitudes of phenotypic variances in peripherally isolated populations of common chaffinches (Fringilla coelebs) in the Azores, Madeira, and Canaries relative to their continental source populations in Iberia and Morocco have played a pivotal role in the formulation of competing hypotheses of phenotypic evolution in these isolates. Because Van Valen's niche variation hypothesis and Grant's model of island evolution were based on museum skins prone to measurement error and temporal variation, we re-examined the patterns of phenotypic variability using more precise skeletal measurements from freshly collected specimens. Levene's tests showed that univariate character variances were homogeneous in all island and continental populations, although there was a consistent trend for the magnitude of the variances to be lower for all characters in all Canary island populations. Multivariate Levene's tests, however, revealed significantly reduced total variances in the Hierro and Madeira populations compared to some Azores and continental populations. The Azores and continental populations did not differ in variability, and lower variances in the Canaries were not related to the presence or absence of the congeneric blue chaffinch (F. teydea), contrary to the predictions of Van Valen's niche variation hypothesis. Population variability was not inversely related to differentiation or isolation within the Azores or Canaries archipelagoes, opposite to the association reported by Grant. Our results also differ from both previous studies which reported much larger differences in population variabilities, and this likely reflects the use of heterogeneous samples of museum specimens, less precise external characters, and the use of tests sensitive to sample size. Differentiation among populations has been markedly greater in the Canary islands, implicating founder events and possibly historically stronger directional selection as determinants of this enhanced divergence relative to the Azores. These variance-reducing processes are unlikely to explain current lower levels of phenotypic variability because there has been sufficient time since colonization for replenishment of variability in polygenic characters. Average heterozygosities at putatively neutral allozyme loci are 1.6 times higher in the Azores compared to the Canaries, and support the view that effective population sizes are smaller in the latter archipelago. We argue that reduced variances in the Canary island populations represent lower equilibrium levels maintained by drift and mutation in populations with smaller long-term effective sizes, consistent with Lynch and Hill's neutral model of phenotypic evolution. Although episodes of selection in the past may have been interspersed with long periods of effective neutralism and drift, adaptationist hypotheses invoking a primary role for variance-reducing selection appear to be unwarranted.     

CONTRASTING GERMINATION AND SEEDLING GROWTH OF BETULA ALLEGHANIENSIS AND RHUS TYPHINA SUBJECTED TO VARIOUS AMOUNTS AND TYPES OF PLANT LITTER

Several characteristics of the environment, such as plant litter, may interact with species characteristics, such as seed size, to determine patterns of plant establishment and thereby influence abundance and spatial location of plants long after the factor has itself disappeared. To determine if litter might differentially affect seedling establishment of Betula alleghaniensis Britton and Rhus typhina L., two woody species with different sized seeds, we conducted two greenhouse experiments. We documented emergence, morphology, and growth patterns of seedlings covered by three amounts each of Fagus grandifolia Ehrh. leaves or Tsuga canadensis L. needles. All amounts of litter significantly reduced and delayed final Betula alleghaniensis seedling emergence, and the resultant seedlings had reduced root: shoot ratios, longer hypocotyls, and were less robust. Litter did not affect Rhus typhina emergence but did alter biomass allocation: stem, leaf, and root biomass of Rhus seedlings was reduced by greater amounts of litter, and by leaf litter relative to needle litter. We attribute the different responses of Betula and Rhus to differences in seed size (Betula mean seed size = 1.0 mg; Rhus mean seed size = 8.5 mg) and germination cues (Betula requires light, Rhus requires chemical or heat scarification), and suggest that differential response to litter may contribute to coexistence among these sympatric species.     

稀土元素对甜菜种子萌发,幼苗生长及块根产量的影响

本文研究了稀土元素对甜菜的生物效应。结果表明,稀土元素可显著地提高种子萌发率,促进幼苗生长,增加幼苗根系活力、叶片净光合速率与块根产量,并明显地降低了甜菜叶片细胞膜在低温下的透性,即提高了叶片的抗寒力。     

黄腐酸和汪平酸对小麦种子萌发与幼苗生长及绿豆下胚轴生根的影响

用黄腐酸和汪平酸浸种后,对于小麦种子萌发无明显影响。用不同浓度的黄腐酸和汪平酸溶液培养小麦幼苗,发现适当浓度时对于幼苗及根系生长与分化有促进作用,高浓度则表现为抑制作用。10ppm黄腐酸和50ppm汪平酸可显著增加去根绿豆下胚轴再生根数,而且在一定的浓度范围内,随着浓度的增高,根数不断增加而根长却逐渐减短。