ACTION OF KINETIN ON PHOTOSENSITIVE GERMINATION OF LETTUCE SEED AS COMPARED WITH THAT OF GIBBERELLIC ACID

1. Experiments with the seeds of Grand Rapids lettuce showedthat the germination induced by gibberellic acid or by red lightis strongly accelerated by kinetin, although the latter itselfcan promote the germination in the dark only slightly. The reversiblelight reactions of the phytochrome system interact with kinetintreatment just as effectively as with water-imbibed controls.The site of primary action of red light is not altered by kinetintreatment. Kinetin does not modify the water uptake of the seedsfor at least 8 hours. 2. Kinetin was found to inhibit the growth of the hypocotyland root of the seed, but to promote very markedly the expansionof the cotyledons. This effect was observed not only with cotyledonsin intact seeds but also with isolated cotyledons. The expansionof kinetin-treated cotyledons is further promoted by red light,but not by far-red, as is also the case with germination itself. 3. A number of purine derivatives which have been reported topromote germination also cause expansion of isolated cotyledons. 4. Gibberellic acid promotes both hypocotyl elongation and cotyledonexpansion in the dark, but this effect does not interact withthe phytochrome system. The site of action of gibberellic acidprobably lies in the axis. 5. It is concluded, therefore, that the site of kinetin actionis in the cotyledons, whose expansion helps to break the seed-coatwhen light or gibberellin has contributed the primary stimulus. ¹ Present address: Johnson Foundation for Medical Physics, Universityof Pennsylvania, Philadelphia, Pa. (Received January 16, 1963; )     

THE ROLE OF THE SEED-COATS IN GERMINATION OF PHOTOSENSITIVE LETTUCE SEEDS

1. In order to analyze the role of both the fruit-coat and theendosperm in the germination of Grand Rapids lettuce seed andin the elongation of the embryo, the seeds were subjected toa number of operations. The fruit-coat was found to make onlya minor con tribution to the photosensitivity of the seed. Thefact that 100% germination of these seeds can occur in completedarkness, when the restraining influence of the endosperm isremoved by appropriate cuts, makes clear that it is the integrityof the endosperm layer that lecides the photosensitivity ofthe seed to red and far-red light. Thus it is deduced that theeffect of light is exerted primarily on the mechanical propertiesof the endosperm layer.
2. Neither red nor far-red light wasfound to affect the elongationof the radicle of de-coated seeds,whereas both powerfully affectthe germination of intact seeds.It follows that radicle elongationis not itself the limitingfactor in germination, although ofcourse it follows immediatelyupon the germination process proper.
3. In order to account forthe ability of red light to initiategermination, it is proposedthat the final step in the germinationcontrol process is theproduction of an enzyme whose actionenables the tip of theradicle to penetrate through the coat.This makes it possiblefor the radicle to begin elongating.Although the detectionof such an enzyme in the radicle wasnot successful, the cotyledonsdo produce both a pectinase andan enzyme hydrolyzing carboxymethylcellulose.Furthermore, seedsinjected with a cellulolytic, hemicellulolyticor pectolyticenzyme germinated to nearly the maximum extentin the dark.This gives considerable support to the hypothesis.

¹ Present address: Johnson Foundation for Medical Physics, Universityof Pennsylvania, Philadelphia, Pa., U. S. A. (Received December 5, 1962; )     

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.     

NaCl胁迫对豫棉112种子萌发,幼苗生长及愈伤组织产生的影响

系统研究了ＮａＣｌ胁迫对豫棉１１２种子萌发,幼苗生长和不同外植体愈伤组织形成的影响。结果表明：ＮａＣｌ对种子萌发,幼苗生长有抑制作用,浓度愈高,抑制作用愈显著;低浓度ＮａＣｌ对子叶,胚轴愈伤组织诱导率没有影响,浓度升高,诱导率明显下降。     

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。     

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.     

TEMPERATURE EFFECTS ON SEED GERMINATION OF EAST ASIAN AND TERTIARY RELICT SPECIES OF DIOSCOREA (DIOSCOREACEAE)

To obtain information relevant to the evolution of dormancy, germination responses to temperature of intact seeds and naked zygotic embryos were compared among taxonomically closely related species of Dioscorea in the section Stenophora. We examined five species from the northern half of the East Asian distribution area and four species considered to be Tertiary relict species from the Appalachians, the Caucasus, and the Balkans. Although features of germination of the intact seeds differed from species to species, the naked embryos of all species germinated over a similar wide range of temperatures without any marked differences among species. This unitary physiological feature of the embryos suggests the possibility that the temperature responses of the embryos have not changed since the Tertiary period. In the East Asian species, as the distribution area shifts to the north the seeds gradually lose their dormant features, and consequently the germination behavior of the seeds gradually changes to resemble that of their embryos. The seed of the northernmost species has no dormant features at all, and temperature responses of the seed are the same as those of the embryo. Full germination of the intact seeds of East Asian and Tertiary relict species required prior chilling treatment. Unlike the East Asian species, however, the relict species germinated to some extent at higher temperatures over a narrow range without prior chilling. However, the resultant germlings died or elongated poorly. Thus, the germination process of relict species may have become less sensitive to high-temperature inhibition after their isolation from Asian species.     

多胺和赤霉素在莴苣种子萌发中的作用及其相互关系

非感光性莴苣（挂丝红品种）种子于２２℃下萌发率在８０％左右,而２８℃下不萌发。２２℃下外源亚精胺显著促进种子萌发,多胺生物合成抑制剂ＤＦＭＡ和ＤＣＨＡ明显抑制种子萌发,而ＤＦＭＯ无效。２２℃诱导种子萌发过程中内源腐胺和亚精含量显著高于２８℃下它们的含量。ＧＡ３处理能诱导２８℃下种子的萌发,单独外源亚精胺处理效果不大,而外源亚精胺对ＧＡ３诱导效应有促进作用。ＤＦ－ＭＡ和ＤＣＨＡ能抑制ＧＡ３诱导２８℃     

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。     

温度对喜马拉雅低额溞生长与生殖的影响

对采自中国云南省高海拔地区-稀有低额溞-喜马拉雅低额溞(Simocephalus himalayensis)在低海拔地区实验室内不同温度梯度下的生长及生殖能力进行了研究.结果表明:高海拔地区生活的低额溞在低海拔地区的相应环境中同样生长繁殖良好,其繁殖率、最大生殖量及种群的增长能力不受海拔高度及不同环境条件的影响.在一定温度条件下(15-31℃,误差为±1℃),喜马拉雅低额溞的发育速率随温度的升高而加快,但在32℃时减慢.在通常培养条件下,喜马拉雅低额溞一般有4个幼龄期(15℃时部分溞体有5个幼龄),16-19个成龄,平均寿命通常为74d(15℃)、54d(20℃)、39d(25℃)和24d(30℃).平均总产仔量在15-25℃最高,分别为449个(15℃)、482个(20℃)和447个(25℃).各温度梯度下的体长增长模型都表明,其体长与龄期之间存在显著的对数关系.每溞平均生殖量以20℃时最高,种群的内禀增长率(rm)和一生的生殖次数都以25℃时最高,净增殖率(R0)以20℃最高.喜马拉雅低额溞最适合的繁殖温度范围在15-25℃.研究还对该种与相应种类在不同温度条件下的生殖量和生物学特性进行了比较.     

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．     

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.     

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.     

THE EFFECT OF SALINITY AND TEMPERATURE ON THE GERMINATION OF POLYMORPHIC SEEDS AND GROWTH OF ATRIPLEX TRIANGULARIS WILLD.

Polymorphic seeds of Atriplex triangularis were germinated at various temperatures (5–15 C, 5–25 C, 10–20 C, 20–30 C) and salinity regimes (0 to 1.5% NaCl) in order to determine their germinability and early seedling growth under these conditions. Larger seeds generally had a higher germination percentage in saline medium. The rate and percentage of germination decreased with increased salinity stress. A thermoperiod of 25 C day and 5 C night, 12 hr/12 hr, temperature enhanced germination of seeds. Early seedling growth is promoted in larger seeds at lower salinity, and at high-day and low-night temperatures. Polymorphic seeds have different physiological requirements which provide alternative situations for seed germination in natural habitats.