干旱胁迫对鹿角杜鹃种子萌发和幼苗生理特性的影响

为探明鹿角杜鹃种子萌发和幼苗生长期的耐旱性,以鹿角杜鹃干种子和90d苗龄幼苗为材料,采用聚乙二醇(PEG-6000)模拟不同程度的干旱胁迫,研究干旱胁迫对其种子萌发、早期幼苗生长及幼苗的细胞膜透性、MDA含量、有机渗透调节物质和抗氧化酶活性的影响,并对种子萌发率、早期幼苗生长量与PEG胁迫浓度间进行了回归分析。结果表明:(1)5%~25%PEG胁迫范围内,随着干旱胁迫程度的增加,鹿角杜鹃种子的发芽启动时间推迟,发芽持续时间延长,发芽率、发芽势、发芽指数、活力指数和幼苗生长量显著降低;重度干旱胁迫(25%PEG)下,鹿角杜鹃种子完全未萌发。(2)发芽率、发芽势、发芽指数、活力指数以及幼苗生长量的变化均与干旱胁迫程度呈极显著负相关关系,回归分析求得鹿角杜鹃种子萌发的半致死PEG干旱胁迫浓度为15.68%、半致矮PEG干旱胁迫浓度为15.37%。(3)随着PEG胁迫浓度的增加,鹿角杜鹃幼苗叶片SOD活性呈先升后降的趋势,但各胁迫处理仍显著高于CK(0%PEG);细胞膜透性、MDA、脯氨酸、可溶性糖含量、POD和CAT活性则在中度(15%~20%PEG)和重度胁迫下显著升高,与干旱胁迫程度呈极显著正相关关系。研究表明,干旱胁迫显著抑制了鹿角杜鹃种子萌发和早期幼苗生长,使其细胞膜受到损伤,同时鹿角杜鹃可通过体内渗透调节物质和抗氧化酶活性的增加来适应干旱环境,使得自身受抑制、损伤程度降到最低。     

入侵植物牛膝菊种子萌发对PEG模拟干旱胁迫的响应

采用浓度分别为5%、10%、15%、20%和25%的PEG-6000溶液模拟干旱条件,测定不同干旱胁迫条件下牛膝菊的种子萌发时间、萌发率、日相对萌发率、发芽势、发芽指数、活力指数及幼苗的初生根与胚芽的长度等指标,研究了干旱胁迫对牛膝菊种子萌发及幼苗生长的影响,探讨了经PEG浸种预处理后种子的萌发恢复能力。结果表明:随着水分胁迫的加重,牛膝菊种子萌发和幼苗生长受到抑制程度增加,牛膝菊种子的日相对萌发率、发芽率、发芽势和发芽指数、活力指数及幼苗的初生根长和胚芽长均呈下降趋势;与对照组相比,牛膝菊种子首次萌发时间延迟越长,当PEG浓度为20%、25%时牛膝菊种子未见萌发;本研究建立了水分胁迫PEG浓度与种子萌发率的线性回归方程,得出牛膝菊种子萌发的PEG浓度临界值为12.9%;经PEG浓度为20%、25%处理的种子在适宜条件下可以恢复萌发,浸种时间相同条件下,20%PEG浓度对牛膝菊种子伤害较小,其恢复性较强,25%PEG浓度对牛膝菊种子伤害较大,其恢复性较弱。     

干旱胁迫对远志种子萌发及幼苗生长和生理特性的影响

以远志(Polygala tenuifolia Willd.)为研究对象,采用不同浓度(2.5%~25%)聚乙二醇(PEG-6000)模拟不同程度的干旱胁迫,探讨干旱胁迫对远志种子萌发及幼苗生理生化特性的影响。结果表明:(1)随着干旱胁迫强度的增加,远志种子的发芽启动时间推迟,发芽率、发芽势、发芽指数和活力指数降低,但种子发芽率在2.5%~15%PEG胁迫下与对照无显著性差异,而在20%PEG胁迫下均显著低于对照,在25%PEG胁迫下种子不能萌发;在干旱胁迫条件下,远志幼苗生物量降低,胚芽生长受到显著抑制,胚根长度则先伸长后缩短。(2)远志幼苗叶绿素含量在2.5%~10%PEG范围内随胁迫强度的增加和时间的延长而持续上升,在15%和20%PEG胁迫下则表现为先上升后下降,在10%PEG胁迫处理第15天时含量最高,为对照的1.34倍。(3)幼苗叶片的游离脯氨酸、可溶性糖和可溶性蛋白含量随PEG胁迫强度的增加和时间的延长而增加,各指标均在20%PEG胁迫处理第15天时含量最高,分别为对照的1.99倍、1.53倍和1.50倍。(4)随着PEG胁迫时间的延长,远志幼苗叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性先上升后下降,并在10%PEG胁迫处理第10天时活性最强;过氧化物酶(POD)活性随着胁迫时间的延长表现出先上升后下降又上升的特性,并在20%PEG胁迫处理第5天时活性最强;叶片丙二醛(MDA)含量在15%和20%PEG胁迫处理下持续上升,在2.5%~10%PEG胁迫范围内先上升后又有所下降。研究发现,远志种子在轻、中度干旱胁迫下仍可正常萌发,而且幼苗能通过调节自身生长、渗透调节物质含量和抗氧化酶活性主动适应干旱环境,对干旱环境表现出较好的适应能力。     

盐胁迫下黄芩种子萌发及幼苗对外源抗坏血酸的生理响应

以黄芩(Scutellaria baicalensis)种子为材料,用氯化钠(Na Cl)模拟盐胁迫条件,采用纸上发芽,研究外源抗坏血酸(As A)对盐胁迫下黄芩种子萌发及幼苗的影响。结果表明,在80 mmol·L-1 Na Cl胁迫下,黄芩种子萌发及幼苗生理指标受到显著抑制;0.50 mmol·L-1 As A处理可显著提高盐胁迫下黄芩种子的发芽势(GE)、发芽率(GR)、发芽指数(GI)、简化活力指数(SVI)以及根系总黄酮、可溶性糖和脯氨酸(Pro)含量,同时也可显著提高幼苗根系活力和超氧化物歧化酶(SOD)活性,显著降低丙二醛(MDA)含量。这说明适宜浓度的抗坏血酸能提高黄芩种子的萌发能力和幼苗对盐胁迫的适应能力,从而起到缓解盐胁迫对种子萌发及幼苗生长的抑制作用。     

模拟水分胁迫对不同种源麻楝种子萌发能力的影响

以麻楝6个种源种子为试验材料,用不同浓度的聚乙二醇(PEG)溶液模拟干旱胁迫,探讨干旱胁迫对种子发芽率、发芽势、发芽指数、活力指数以及幼苗苗高和胚根长及根苗比的影响,为麻楝的引种和推广种植提供依据。结果显示:(1)不同水势胁迫处理均降低了麻楝种子的发芽率和发芽势,当水势为-0.40MPa时延缓了种子萌发进程;种子的发芽率、发芽势、发芽指数和活力指数均随干旱胁迫强度的增加呈明显下降的趋势;当胁迫水势为-0.86MPa时,干旱胁迫处理的种子在试验结束时仍未能萌发,即-0.86MPa是麻楝种子萌发的临界水势。(2)当胁迫水势高于-0.40MPa时,麻楝幼苗的胚根长度与对照组差异不显著且长于对照组,说明高于-0.40MPa的水势有利于麻楝种子胚根的生长;麻楝幼苗苗高生长则是随着PEG浓度的升高而逐渐减缓。(3)适当的干旱胁迫可以增大各种源麻楝幼苗根苗比,且在胁迫水势高于-0.20MPa时都达到最大值。研究表明,麻楝种子具有一定的抗干旱胁迫的萌发能力,并以来自缅甸的Khin Aye Pale和泰国的Phu Wiang材料较强,来源于中国三亚和马来西亚Ulu Tranan的较弱。     

外源5-氨基乙酰丙酸对干旱胁迫下甘草种子萌发及幼苗生理特性的影响

以药用植物甘草种子和幼苗为材料,在20%PEG-6000模拟干旱胁迫条件下,测定了不同浓度外源5-氨基乙酰丙酸(ALA)处理甘草种子的发芽势(Gv)、发芽率(Gr)、发芽指数(Gi)和活力指数(Vi)的变化,以及ALA处理幼苗叶片的质膜透性、丙二醛(MDA)含量、可溶性糖含量、游离脯氨酸含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性。结果显示:(1)在20%PEG-6000胁迫下,甘草种子萌发受到显著抑制,而各项萌发指标经过不同浓度的ALA进行恢复处理后均有明显提高,且均以10 mg.L-1ALA处理的各项指标值最大,其种子发芽势(75%)、发芽率(91%)比干旱胁迫对照显著提高了35%和30%,发芽指数(36.2)和活力指数(709.7)分别提高至干旱胁迫的2.6和3.5倍。(2)各ALA处理较对照均显著提高了干旱胁迫下甘草幼苗总生物量、可溶性糖的含量及脯氨酸含量,却显著降低了甘草叶片的MDA含量和质膜透性,同时显著提高了干旱胁迫下甘草叶片中的SOD、POD和CAT的活性,且以10 mg.L-1ALA处理后的酶活性最强。研究表明,适宜浓度(10 mg.L-1)的ALA能显著提高干旱胁迫下甘草种子的萌发能力,通过调节渗透调节物质含量和保护酶活性来有效减缓干旱胁迫对甘草幼苗的伤害,提高甘草种子及幼苗的抗旱能力。     

PEG-6000模拟干旱胁迫对黄秋葵种子萌发和幼苗生理特性的影响

为了解黄秋葵(Abelmoschusesculentus)对干旱胁迫的应答机制,采用PEG-6000溶液模拟干旱胁迫,对‘纤指’和‘红秋葵’品种的种子萌发和幼苗的生理特性进行研究。结果表明,两品种的种子吸水率、发芽势、发芽率、发芽指数、活力指数、简易活力指数,幼苗下胚轴长、根长、苗鲜重和苗干重均随PEG-6000浓度的增加呈下降的趋势,旱害率则不断增加。PEG-6000浓度为20%时,两品种的种子均未能发芽。幼苗的SOD、POD和CAT活性和可溶性蛋白、可溶性糖、游离脯氨酸、丙二醛含量随PEG-6000浓度的增加而增加,且均PEG-6000浓度为15%时最高。因此,干旱胁迫会抑制黄秋葵种子的萌发,提高细胞内含物的含量,同时引发其抗氧化系统的响应。     

PEG胁迫对紫茎泽兰种子萌发和幼苗生长的影响

目的：开展干旱胁迫对紫茎泽兰种子萌发的影响研究，为其入侵机制的揭示和田间防治提供借鉴。方法：采用聚乙二醇（PEG-6000）梯度溶液模拟干旱胁迫环境，研究紫茎泽兰（Ageratina adenophora）种子萌发和幼苗生长对干旱胁迫的响应。结果：随着PEG-6000浓度的增加，紫茎泽兰种子的发芽率、发芽势、发芽指数和幼苗根长、根冠比均呈先升后降的趋势，而种子活力指数、幼苗胚根长度、胚轴长度、株高相对增长速率和叶片光合色素含量均呈持续下降趋势。结论：轻度干旱胁迫有利于紫茎泽兰种子萌发，而中度和重度干旱胁迫均不利于紫茎泽兰幼苗生长。紫茎泽兰在种子萌发阶段对干旱具有一定的抗逆性。     

Cd胁迫对紫花苜蓿种子发芽及幼苗生理生化特性的影响

以‘甘农3号’紫花苜蓿(Medicago sativa L.cv.‘Gannong 3’)品种为试验材料,研究不同浓度Cd胁迫对紫花苜蓿种子萌发及幼苗生理生化特性的影响。结果显示:(1)Cd胁迫显著抑制紫花苜蓿种子萌发及幼苗生长,种子发芽势、发芽率及幼苗的胚芽长、胚根长和干重均随着Cd处理浓度提高显著降低,且对发芽势的抑制作用大于发芽率,对胚根生长的抑制作用大于胚芽。(2)Cd胁迫第4d时,萌发种子中蛋白水解酶的活性受到显著抑制,可溶性蛋白和可溶性糖含量显著降低。(3)Cd胁迫第10d时,随着Cd胁迫浓度的增加,苜蓿幼苗的超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、愈创木酚过氧化物酶(GPX)活性均先升高后降低,过氧化氢酶(CAT)活性持续下降,超氧阴离子自由基产生速率、H2O2含量和丙二醛(MDA)含量均显著增加。研究表明,低浓度Cd胁迫下,苜蓿幼苗抗氧化系统清除活性氧的能力上升,高浓度Cd胁迫下,苜蓿幼苗抗氧化系统活性下降,膜脂过氧化程度加剧,活性氧的过量积累是Cd伤害苜蓿幼苗和其生物量下降的主要原因。     

外源Ca2+浸种对Cd2+胁迫下红三叶种子萌发和幼苗生长及其生化特性的影响

用不同浓度Ca2 溶液浸种处理红三叶种子后、用0.1 mmol·L-1Cd2 溶液培养,探讨外源Ca2 对Cd2 胁迫下红三叶种子萌发、幼苗生长及其保护酶活性和子叶叶绿素含量的影响.结果显示:(1)0.1 mmol·L-1Ca2 浸种处理能显著缓解Cd2 胁迫的影响,可使红三叶种子发芽势、发芽指数及活力指数显著升高,全苗长、胚根长和胚根/胚芽显著增加(分别增加21.38%、44.06%和38.63%),并显著提高叶绿素含量(14.59%);(2)0.11、.0 mmol·L-1Ca2 浸种预处理均能显著提高Cd2 胁迫下红三叶幼苗子叶SOD活性(43.17%、218.95%)和POD活性(34.00%、14.28%),并显著降低其CAT活性(17.43%、29.19%)和MDA含量(21.92%、24.51%).结果表明,0.1mmol·L-1外源Ca2 浸种处理能显著缓解Cd2 (0.1 mmol·L-1)胁迫对红三叶种子萌发及幼苗生长及其保护酶活性的抑制作用,可明显提高红三叶幼苗对Cd2 胁迫的抵抗能力,缓解效果最优.     

Seed morphology and anatomy in someAnnonaceae

Twelve species ofAnnonaceae, namelyAncana sp.,A. stenopetala, Annona cherimola, A. montana, A. muricata, A. squamosa, Bocagea sp.,Bocageopsis canescens, two species ofUnonopsis, Xylopia aromatica, andX. emarginata, were investigated with respect to the morphology and anatomy of the seed. They show the basic structural pattern characteristic of annonaceous seeds: perichalaza, fibrous mesotesta, and rumination developed by both integuments. However, several differential characters, some of them never previously described, were found: All taxa exhibit an additional endotestal mechanical layer which forms the micropylar plug except inAncana. InAncana the plug is built by the inner integument. Aril, sarcotesta and pits on the seed surface are present in some taxa and show different origin and structure. Special anatomical adaptations possibly functioning during germination are described. The results obtained from the investigated taxa are discussed and compared with published data on seed structure inAnnonaceae.     

Implications of Seed Proteins in Brassicaceae Systematics

Seed proteins of eleven species of Brassicaceae were investigated by polyacrylamide gel electrophoresis. In total 50 different bands were identified. Some of the bands are characteristic and represent constant markers of each species, which allow the unequivocal identification of their electrophoregram. The obtained data have been treated numerically using the cluster analysis method of unweighed pair group (UPGMA). The electrophoregram gives support to the idea that the tribe Sisymbrieae is an unnatural group and suggests its merge with the tribe Brassiceae. On the other hand the distinct position of Zilla spinosa in the dendrograms supports the traditional treatment of this taxon as a monotypic subtribe Zillinae.     

Seed development in Pisum

The Ih and lh _i alleles have been shown previously to reduce the level of endogenous gibberellin A₁ (GA₁) in shoots of pea (Pisum sativum L.), resulting in a dwarf phenotype compared with the wild type, cv. Torsdag (Lh). In addition, plants homozygous for the lh ⁱ allele have reduced seed yield compared with Lh (tall, wild type) and lh (dwarf) plants. In this paper we show that the lh ⁱ mutation is expressed in developing seeds and pods. Comparison of GA levels in young shoots and developing seeds of genotypes lh and lh ⁱ demonstrates that the relative severity of the two mutations varies in different tissues. Homozygous h ⁱ seeds have reduced GA levels, weigh less, and are less likely to develop to maturity when compared with Lh seeds. However, fertilization of lh ⁱ plants with Lh pollen increases seed GA levels, seed weight and seed survival, indicating that an increase in seed GA levels due to the presence of the Lh allele can restore normal seed growth. Pods developing on self-pollinated lh ⁱ plants are shorter than pods on Lh (wild type) plants, although this may be an indirect effect of the increased seed abortion of lh _i plants. Based on these results we suggest that endogenous GAs play an important role in the development of seeds of P. sativum L.Abbreviations GA_(n) gibberellin A_n We wish to thank Katherine McPherson, Peter Newman, Leigh Johnson and Peter Bobbi for technical assistance, Professor L. Mander (ANU, Canberra) and Professor B.O. Phinney (UCLA, USA) for labelled GA standards, and the Australian Research Council for financial support.     

Seed morphology in Southern AfricanOrchidoideae (Orchidaceae)

The seed morphology of 151 species of Southern AfricanOrchidoideae (Orchideae andDiseae; sensuDressler 1981) was studied by means of scanning electron microscopy. Two different seed types were found. (1) In the majority of species the seeds are minute and fusiform. The seed coat is made up of comparatively few concave and elongate testa cells with straight or slightly undulate and generally unthickened anticlinal cell walls. The seed type was here termed Satyrium-type. While most species are very similar in the ornamentation of the periclinal walls of their seed coat, considerable variation was found inHolothrix where two distinct groups can be recognized in this respect. (2) A remarkably different seed type was observed inDisa uniflora and three apparently closely related species (Disa uniflora-type), where large balloon-like seeds occur. Their seed coat consists of convex cells with undulate anticlinal walls. It is suggested that this seed type is a derived condition and has evolved in adaptation to the specialized habitat alongside streams. The possibility of hydrochory in these four species is briefly discussed.     

Seed protein electrophoresis in sectionFoenum-graecum ofTrigonella (Fabaceae)

The seed proteins ofTrigonella foenum-graecum, T. berythaea, T. macrorrhyncha andT. gladiata were fractionated on polyacrylamide gels in anodic and cathodic systems. Similarity indices between the profiles of any two species indicated close affinity betweenT. gladiata andT. macrorrhyncha and betweenT. foenum-graecum andT. berythaea. It has been pointed out that according to morphological resemblance and similarity index of the seed protein profileT. berythaea is closer to the cultigen than any other species of sectionFoenum-graecum, but these two species are strongly isolated from one another by the albino seedlings of their F₁ hybrids.     

Seed Storage Proteins in Solanaceae and Cucurbitaceae Species

Electrophoretic analyses of non-reduced and reduced seed storage proteins from Solanaceae and Cucurbitaceae species and cultivars were performed. High molecular disulfide bonded complexes between intermediary subunits of 11S globulins previously detected in Capsicum annuum cultivars, were found in Solanum melongena cultivars as well. The data obtained might be used for further elucidation of peculiarities of the 11S globulins in dicotyledonous plants.     

Effects of Seed Dispersal by Three Ateline Monkey Species on Seed Germination at Tinigua National Park, Colombia

We examined the effect of seed ingestion by three ateline primates: woolly monkeys, Lagothrix lagothricha; spider monkeys, Ateles belzebuth; and, red howler, Alouatta seniculus on germination rates and latency periods of seeds of several plant species in Tinigua National Park, Colombia. We collected dispersed seeds from feces and control seeds from the parental trees and washed them for germination trials. For the majority of plants, dispersed seeds germinated as well or better than control seeds did. Although spider monkeys depend more heavily on fruits than the other monkey species do, they were not more efficient than howlers or woolly monkeys at improving germination rates. A considerable proportion of the seeds dispersed by howlers and woolly monkeys showed reduced latency periods to germination, but spider monkeys showed less effect on reducing germination time. This result may be related to longer gut retention times, but such a trend has not been observed in other primate species. We conclude that, like many other primates, ateline monkeys are effective seed dispersers in terms of their effects on the seeds they swallow because they rarely decrease their germination rates. We discuss problems that make interspecific comparisons difficult, such as inappropriate control seeds and differences associated with germination substrates, and we stress the importance of studying other components of seed dispersal effectiveness.     

Seed flavonoids of thePodalyrieae andLiparieae (Fabaceae)

A study of the phenolic compounds of the closely related papilionoid tribes,Podalyrieae andLiparieae, proved that the flavonoid patterns of hydrolysed seed extracts are remarkably conservative. Butin (7, 3, 4-trihydroxyflavanone), 3-hydroxydaidzein (7, 3, 4-trihydroxyisoflavone), vicenin-2 (6, 8-di--D-glucopyranosyl-5, 7, 4-trihydroxyflavone) and orobol (5, 7, 3, 4-tetrahydroxyisoflavone) were isolated and identified as the major flavonoids. The seeds ofAmphithalea, Coelidium, Liparia, Xiphotheca, Calpurnia, Stirtonanthus andPodalyria accumulated three isoflavone O-glycosides that yielded 3-hydroxydaidzein on hydrolysis. In contrast,Virgilia contained a unique combination of vicenin-2 and orobol. Vicenin-2 was also present inCalpurnia as a major compound, butStirtonanthus insignis was the only other species studied that contained orobol (in trace amounts only). Butein, a chalcone, was reported byHarborne from the seed ofCyclopia subternata. This compound's flavanone analog, butin, was the principal component inCyclopia. A cladistic analysis, using flavonoid, alkaloid and morphological data, showed that the seed flavonoids of thePodalyrieae andLiparieae behave rather poorly as cladistic characters. They are, however, of considerable taxonomic value at the tribal level favouring the opinion that the two tribes should be combined. The apparent absence of flavonoids in the seed ofHypocalyptus supports the suggestion that it should be excluded from theLiparieae. Flavonoids also show that theArgyrolobium-group is very different from the tribeCrotalarieae and support the recent transfer of this group to the tribeGenisteae.     

1.5代杉木种子园不同无性系生长和结实性状的评价

为进一步优化1.5代杉木种子园的质量,通过对福建漳平杉木种子园内21个杉木无性系生长和球果特征的调查,分析不同无性系生长和结实性状的差异及其相互关系,采用层次分析法对不同无性系的生长性状和结实性状进行综合评价。结果表明:1.5代杉木种子园不同无性系之间的生长和结实性状存在明显差异;不同无性系的结实量、球果体积、球果鲜重与其种子产量显著相关,生长性状与结实量、结实量与种子发芽率的相关性不显著。根据不同无性系生长性状和结实性状的综合评价结果,有6个无性系具有生长快且结实量高的特性,可作为重建1.5代杉木种子园的材料。     

金沙江干热河谷滇榄仁种子扩散与种子库特征研究

采用随机取样和跟踪调查的方法对滇榄仁(Terminalia franchetii)种子扩散规律、空间分布特征以及种子库动态进行了系统研究。结果表明,滇榄仁种子扩散受到较强的风力作用影响,具有明显的方向性,扩散距离是其树高的1.6倍以上。不同群落类型中,滇榄仁的土壤种子库存在较大差异,但不同时间段的变化趋势基本一致,即在雨季(6月、8月和10月)数量相对较少,12月到翌年4月,数量逐渐增加。滇榄仁植冠种子库从当年10月开始缓慢脱落,到翌年3月达到脱落高峰(15%以上种子此时脱落),然后再次进入缓慢脱落期,翌年6、7月的种子脱落速率最低,但直到翌年10月仍有部分种子(约15%左右)存在于植株冠层。总体来说,不同类型群落中,滇榄仁幼苗更新不良的原因不应是缺乏种源,可能与种子质量以及群落环境等影响群落天然更新的其它因子存在较大关联。同时,滇榄仁土壤种子库数量与植冠种子库的脱落过程存在紧密联系,而植冠种子脱落可能与该区域气候因子存在着较大依存关系,其中,与风力可能存在着正相关,与降雨量和空气相对湿度存在着负相关,这可能是滇榄仁长期以来对干热河谷环境的一种适应特征。