THE EFFECTS OF TEMPERATURE ON THE GERMINATION AND RADICLE GROWTH OF PHOTOSENSITIVE LETTUCE SEED

1. The time course of germination of Grand Rapids lettuce seedshas heen followed with different combinations of temperature(3°–35°) and irradiation (red or far-red light).For each set of conditions the following three parameters weredetermined: (i) the time required for half maximum germination,(ii) the rate of germination during the actively germinatingphase, and (iii) the maximum germination attained. In general,as the temperature was lowered, with dark-imbibed seeds, (i)became longer, (ii) became lower, but (iii) became progressivelyhigher. The effect of red light at any temperature was to shorten(i) and increase (ii) and (iii) over the values dark controls.Far-red light exerted an effect opposite to that of red light.Temperatures higher than 25° inhibited (ii) and (iii) underany light conditions. The optimum temperature to the actionof red and far-red light is 25°, at which the stimulatoryeffect of red light and the inhibition of this effect by far-redlight are both maximal. 2. The growth of the radicles of de-coated seeds of Grand Rapidslettuce shows two phases at all temperatures studied. PhaseI is characterized by slow but linear growth which continuesuntil shortly after visible differentiation of the radicle intothe hypocotyl and the root. Phase II is a phase of active growthin which the total length reflects mainly the length of theroot. The optimum temperature for Phase I is 25°-35°,and that, for Phase II is 25°. In neither phase, and atnone of the temperatures studied, is there any effect of redor far-red radiation on the growth of the radicle. The firstvisible sign of radicle elongation in red light induced seeds,however, takes place at exactly the same time as that of germination. 3. Similarities and dissimilarities between the germinationand the growth are pointed out, and it is concluded that thetwo phenomena are different, but proceed at sites closely associatedin the embryo. ¹Present address: Johnson Foundation for Medical Physics, Universityof Pennsylvania, Philadelphia, Pa., U.S.A.     

INTERACTION OF TEMPERATURE AND GIBBERELLIN ON POTATO SEED GERMINATION

Recently harvested true seed of potato frequently requires several months for complete germination. Gibberellic acid (GA₃) has a pronounced effect on seed germination, but this effect is influenced by temperature. As the temperature approaches 80 F, germination decreases considerably irrespective of GA₃ treatment. Potato seed germination is also favored by low temperature, but constant low temperature alone does not insure complete germination of dormant seeds. More than 95% germination of dormant seeds can be obtained within a week either by application of GA₃ at low temperature or by diurnal alternation of temperature. A possible mechanism for control of seed germination is discussed.     

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.     

EFFECTS OF LIGHT AND TEMPERATURE ON SEED GERMINATION OF FICUS HISPIDA IN XISHUANGBANNA, SOUTHWEST CHINA

 该研究应用人工气候箱设置不同的光照和温度梯度, 探讨对对叶榕(Ficus hispida)种子萌发的影响。结果表明, 荧光灯条件下(红光和远红光比例(R/FR)为4.56, 光量子密度(PPFD)约为90 μmol&;#8226;m^–2&;#8226;s^–1), 温度对种子萌发速率有显著影响, 而对最终萌发率的影响不显著。对叶榕的种子为光敏性种子, 萌发严格需光, R/FR对种子最终萌发率的影响显著, 较高的R/FR促进种子萌发, 而较低的 R/FR 抑制种子萌发。光强影响种子的萌发速率, 较弱的光照可以延缓种子萌发, 但并不能完全抑制其萌发。在30 ℃条件下, 对叶榕的种子可以在较高的 R/FR (0.42) 水平下萌发, 但温度为23/20 ℃ 时, 种子对 R/FR 的要求增高, 0.42的R/FR不能导致种子萌发。说明较低的温度和 R/FR 都可以显著抑制对叶榕的种子萌发, 而较高的温度和R/FR皆有利于种子的萌发。     

THE EFFECT OF THE INTERACTION OF TEMPERATURE WITH AFTER-RIPENING REQUIREMENT AND COMPENSATING TEMPERATURE ON GERMINATION OF SEED OF FIVE SPECIES OF ROSA

Seeds of 5 rose species, Rosa multiflora Thunb. ‘Cathayensis,’ R. × reversa Waldst. & Kit., R. setigera Michx. ‘Beltsville,’ R. setigera Michx. ‘Serena,’ and R. wichuraiana Crepin, varied in after-ripening requirement from 30 days at 4.4 C for R. multiflora to 90 days for R. setigera ‘Serena.’ The compensating temperature varied from near 12.8 C for R. × reversa to a value near 29.4 C for R. setigera ‘Beltsville.’ In this report compensating temperature is used to describe that temperature at which mature, moist seed does not germinate, after-ripening does not take place, and dormancy does not change. Seed germination was reduced by interruption of the after-ripening period with intervals at temperatures above the compensating temperature. The interruptions were more effective in reducing germination when more frequent and when the temperature during the interval was higher. Species differed in their sensitivity to high-temperature reduction of germination. Those having the longest after-ripening requirement were most sensitive. Germination of seeds which had the minimum after-ripening treatment was repressed more by high temperature than germination of those seeds which had an excess of after-ripening. The decrease in germination resulted from imposition of a secondary dormancy of the embryo, and probably also from reversal of the after-ripening effect upon the primary dormancy imposed by the seed coat.     

沙埋和种子大小对固沙禾草沙鞭的种子萌发与幼苗出土的影响

该文研究了野外条件下不同深度的沙埋对沙鞭(Psammochloa villosa)种子萌发和幼苗出土的影响,以及温室条件下种子大小对不同深度沙埋后的种子萌发和幼苗出土的影响。结果表明,沙埋深度显著影响沙鞭的种子萌发率、幼苗出土率和种子休眠率。沙子表面的种子不能萌发。2 cm的浅层沙埋时的种子萌发率和幼苗出土率最高,1 cm 沙埋的种子萌发率和幼苗出土率次之。沙埋深度超过2 cm之后,沙鞭的种子萌发率和幼苗出土率与沙埋深度呈负相关。2 cm的种子休眠率最低。从2 ~12 cm,种子休眠率随着沙埋深度的增加而增加。在幼苗能够出土的深度(1~6 cm),幼苗首次出土所需的时间随着沙埋深度的增加而延长。种子大小对沙鞭的种子萌发率没有显著影响。但是在深层沙埋(6 cm)时,与小种子相比,大种子产生的幼苗的出土率较高。从2~6 cm,大种子形成的幼苗的茎长度都较长。     

WATER POTENTIAL,TEMPERATURE, AND KINETIN EFFECTS ON SEED GERMINATION IN SOIL AND SOLUTE SYSTEMS

Germination of lettuce and wheat in soil is reduced by a decrease in water potential, but a significant temperature-water potential interaction exists for lettuce. At 35 C kinetin permits lettuce germination at 0 and —1.1 bars, and at 25 C and 15 C it enhances germination at lower water potentials, causing 30% germination at —8.0 bars. Wheat germinates well at —8.0 bars, but no germination occurs at —14.9 bars; temperature had little effect on wheat germination. Germination in soil and solute systems was compared to determine the usefulness of solute germination data for predicting germination in dry soil. Total germination of lettuce in polyethylene glycol-6000 may approximate total germination in soil at the same water potential, but germination rates differ widely for the two systems. Kinetin-treated lettuce seeds nearly completed germination in two days in polyethylene glycol solutions, but five days were required for similar germination percentages in the soil. Sucrose is not useful for simulating soil water stress; wheat seeds germinate at —14.9 bars in sucrose but fail to germinate in soil at the same potential, and germination is more rapid in sucrose than in the soil.     

光温和化学处理对水青树种子发芽的影响

水青树是一种稀有珍贵树木。它的种子没有休眠,对光的反应随温度而异,25℃时不需光,24—33℃(多在28—30℃)喜光,10—20℃光对发芽有促进作用。最适发芽温度为25℃。经冬季低温层积的种子,可在1.4—8.2℃的低温中发芽。硝酸钾能部分解除种子发芽对温度的要求,GA也略有这种作用。以上结果不仅对水青树的种子检验和播种育苗有实用价值,同时在光温和化学处理对发芽的影响方面,有一定的理论价值。     

几种外源激素对杉木种子萌发的影响

应用ＧＡ、６－ＢＡ和ＡＢＡ等三种外源激素对杉木种于萌发的影响进行了研究．结果表明,ＧＡ较明显促进杉木种子的萌发,而６－ＢＡ和ＡＢＡ则显著地抑制了杉木种子的萌发．当三种激素共同存在时,它们在杉木种子萌发中的相互作用表现为：ＧＡ起促进作用（最适浓度为５０－１００ｐｐｍ）．ＡＢＡ起抑制作用,６－ＢＡ（浓度不超过５０ｐｐｍ）则有解除ＡＢＡ的抑制作用．     

四种植物种子萌发及苗期抗旱性差异的研究

对四种豆科植物种子萌发及苗期抗旱性作了比较研究,结果表示：种子萌发期抗旱笥强的植物其苗期抗旱性亦强。干旱引起组织脱水,植株生长受到抑制,幼苗出现衩始萎蔫时间与细胞膜受害时间一致。四种植物显示萎蔫时土壤含水量明显不同,红豆草为４．８０％、羊柴２．２％、花棒１．７４％、柠条１．５１％．据种子相对发芽率、膜透性变化等生理指标综合评定四种植物种子萌发及苗期抗旱能力次序为：柠条＞花棒＞羊柴＞红豆草。     

VARIATION IN SEED WEIGHT AND ITS EFFECTS ON GERMINATION IN PASTINACA SATIVA L. (UMBELLIFERAE)

Pastinaca sativa (wild parsnip) produces seeds on the primary, secondary, and tertiary umbels of the flowering stalk. Within plants, variation in seed weight is about twofold. Secondary and tertiary seed weight is 73% and 50% of primary seed weight, respectively. Maximum variation in seed weight between plants is sixfold when tertiary seeds from a small plant are compared to primary seeds from a large plant. Within an umbel order, variation in seed weight between plants is correlated with plant size. Under autumn germinating conditions in the laboratory, final germination of seeds from different umbel orders does not differ but smaller seeds germinate more rapidly than larger seeds. Under spring germination conditions in the laboratory, significantly more primary and secondary seeds germinate than tertiary seeds and the rate of germination is independent of seed weight. Field germination of seeds from different umbel orders produces similar results except that in the spring both secondary and tertiary seed germination is lower than that of primary seeds. These results suggest that with respect to seed germination characteristics small seeds may have a competitive advantage over large seeds in the autumn because they germinate more quickly, but in the spring small seeds are at a disadvantage because they have lower overall germination. Because most germination in the field occurs in the spring, population recruitment from small seeds is likely to be substanially less than that from large seeds.     

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.     

溶氧、pH及其他理化因子对蓖齿眼子菜种子萌发的影响

研究了溶氧、pH、光强、冷处理、温度、营养以及激素处理等条件对蓖齿眼子菜种子萌发的影响。结果表明:溶氧对种子的最终萌发率有影响,缺氧条件下比正常条件和氧饱和条件下的萌发率高,但缺氧条件下萌发的幼苗为白化苗,不能正常生长发育;光照和pH对种子萌发的影响不显著。4℃冷处理能够使种子萌发时间提前和提高种子的萌发率;在15—27℃之间,提高温度能够加快种子的萌发速度,但温度过高则萌发率降低,在15℃、20℃和27℃下的最终萌发率分别为90.0%、90.0%和56.7%;不同的营养水平对种子萌发影响不显著。生长素NAA(0.1—5.0mg/L)、细胞分裂素6-BA(0.1—5.0mg/L)、赤霉素GA3(0.1—5.0 mg/L)不能加快蓖齿眼子菜种子萌发的速度和提高萌发率。     

阿司匹林和复方新诺明对大豆种子萌发及活力的影响

 以大豆(Glycine max)种子为材料,浓度的阿斯匹林和复方新诺明水溶液,在(20±1)℃条件下分种24h和12h, 测定大豆种子萌发过程中的各项生理生化指标以及萌发后的各形态指标实验结果表明：阿斯匹林和复方新诺明水溶液浸种都能有效地提高大豆种子的发芽率和活力指数,还能促进大豆根系的生长。其中以62.5mg·L-1的阿斯匹林和0.5mg·L-1的复方新诺明处理后的效果最为显著。阿斯匹林浸种能使大豆萌芽的相对电导率显著降低,使活性氧清除酶的活性有所提高。复方新诺明浸种则使大豆萌芽的蛋白质含量以及氨基酸总量都有显著的提高。     

脱落酸和抑制剂对萌发花生子叶肽链内切酶和花生球蛋白降解的影响

脱落酸（Ａｂｓｃｉｓｉｃａｃｉｄ,ＡＢＡ）抑制花生种子萌发的作用与核酸和蛋白质合成抑制剂的作用不同．ＡＢＡ（１００μｍｏｌ／Ｌ）在萌发零时施用,明显抑制肽链内切酶活性和同工酶表现以及花生球蛋白降解,萌发４８ｈ施用ＡＢＡ（１００μｍｏｌ／Ｌ）只降低肽链内切酶活性．ＡＢＡ的抑制作用不依赖于核酸和蛋白质合成．核酸合成抑制剂（３＇－脱氧腺苷,放线菌素Ｄ,５－氟尿嘧啶）和蛋白质合成抑制剂（亚胺环己酮）只能部分降低肽链内切酶活性,对肽链内切酶同工酶表现和花生球蛋白降解无明显影响．实验结果表明花生子叶肽链内酶不是在种子萌发过程中重新（ｄｅｎｏｖｏ）合成,文中讨论了肽链内切酶活性调节和花生贮藏蛋白降解的起始模式．     

EFFECT OF STRATIFICATION TEMPERATURE AND GERMINATION TEMPERATURE ON GERMINATION AND THE INDUCTION OF SECONDARY DORMANCY IN COMMON RAGWEED SEEDS

Stratification of common ragweed (Ambrosia artemisiifolia) seeds at 4 C was most successful for breaking dormancy, whereas -5 C was least effective and 10 C was intermediate. Germination in the light exceeded that in the dark at all stratification and germination temperatures. The optimum temperatures for germination in the light were 10/20, 15/25, and 20/30. Maximum germination in the dark occurred at 20/30 C for seeds stratified at 4 and 10 C but the optimum temperatures for seeds stratified at -5 C were 10/20, 15/25, and 20/30. Seeds stratified at -5 and 10 C germinated best after 15 weeks of stratification, whereas 12 weeks of stratification at 4 C resulted in maximum germination. Secondary dormancy was induced in seeds which did not germinate in the dark. This was affected by stratification temperature and duration and germination temperature. The ecological significance of these germination characteristics is discussed.     

南亚热带森林几种乔木种子萌发和幼苗生长观察

本文对香椿（Ｔｏｏｎａｓｉｎｅｎｓｉｓ（Ａ．Ｊｕｓｓ．）Ｒｏｅｍ．）、木蝴蝶（Ｏｒｏｘｙｌｕｍｉｎｄｉｃｕｍ（Ｌ．）Ｖｅｎｔ．）、扁斗青冈（ＱｕｅｒｃｕｓｈｕｉＣｈｕｎ）、泡桐（Ｐａｕｌｏｗｎｉａｆｏｒｔｕｎｅｉ（Ｓｅｅｍ．）Ｈｅｍｓｌ）罗浮柿（ＤｉｏｓｐｙｒｏｓｍｏｒｒｉｓｉａｎａＨａｎｃｅ）、枳（ＢｅｒｃｈｅｍｉａｄｕｌｃｉｓＴｈｕｎｂ．）等南亚热带森林乔木种子萌发和幼苗生长进行观察．香椿、扁斗青冈、罗浮柿种子在轻阴（５５％光）条件下萌发率最高,分别为７０％、９０％、３０％,木蝴蝶种子在重阴（３８％光）条件下萌发率最高,为８０％,枳种子在光照条件下萌发率最高,为１５％．阳性树种香椿、木蝴蝶、泡桐、枳幼苗生长速度较快,属速生型树种,其幼苗在光照条件下生长速度最快,森林中树种扁斗青冈、罗浮柿幼苗生长速度较慢,属慢生型树种,其幼苗在轻阴条件下生长较好．随着施肥量的增加,幼苗生长速度明显提高．