Effects of Cultivation on the Germination Character of the Corn Cockle (Agrostemma githago L.)

Germination tests were done on 19 populations of Agrostemmagithago to examine their responses in relation to the culturalhistory of the plant and to try to determine what changes mayhave accompanied cultivation and the part these may have playedin the establishment and subsequent decline of the species asa weed. Differences found from one population to another were foundto be relatively minor, and the responses of all the collectionsresembled those of other species of Silenoideae distributednaturally around the Mediterranean basin. Differences were establishedbetween adventive populations of A. githago and species naturallydistributed in deciduous woodland and steppeland zones of Europe,even when growth patterns and habitat preferences were relativelysimilar. It was concluded that A. githago had originated in an area witha Mediterranean climate and that there had been few changesin the germination responses of the species during its periodof association with man as a weed of cultivation. The significanceof this result is discussed in relation to the decline of thespecies in Europe during the last hundred years, and with respectto the effects of cultivation on the germination of species,including crop plants, of Mediterranean origin which possessgermination responses similar to those of Agrostemma.     

The Effect of Low Temperature Pre-Sowing Treatment on the Germination Performance and Membrane Integrity of Artificially Aged Tomato Seeds

Loss of seed viability and decrease in germination rate appearto be due to two independent sets of events occurring duringartificial ageing in tomato (Lycopersicon esculentum Mill) seeds.Only the second category of physiological damage is reversible:a low temperature pre-sowing treatment being capable of greatlyreducing the time to fifty percent germination of both unagedand aged seeds, but having no effect on germination capacity.Leakage of ionic solutes from the seeds did not increase followingageing, but there were considerable increases in losses of smallorganic molecules. Low temperature pretreatments did not reducethe rate of loss of either amino acids or reducing sugars fromaged seeds. The implications of the use of artificial ageingin combination with low temperature pre-sowing treatments inthe study of small seed physiology is discussed, as is the valueof solute leakage studies in this kind of seed. Key words: Tomato seeds, Accelerated ageing, Seed treatment, Membranes     

Biosynthesis of Storage Proteins in Ripening Agrostemma githago L. Seeds

The synthesis of storage proteins in ripening Agrostemma githago seeds was studied by in vivo pulse and pulse-chase experiments with labeled amino acids and labeled glucosamine. It was found that storage proteins were not synthesized directly, but via cleavage of several large precursor proteins. Two disulfide-linked proteins of 38 and 25 kilodaltons were synthesized via a single large precursor protein. This precursor protein contained internal disulfide bridges, at least one of which is involved in holding the subunit structure together following cleavage of the precursor. A similar mode of biosynthesis was noted for two other disulfide-linked proteins of 36 and 22 kilodaltons. The half-life of the precursors was about 2 hours. This mode of processing is analogous to the synthesis of legumin in legumes and globulin in oats. A third pair of disulfide-bonded proteins (41 and 23 kilodaltons) was synthesized from a precursor protein in several steps. These included a legumin-like cleavage, whereafter the subunits remained disulfide-bonded. Then, from the largest subunit, a part was cleaved off, probably a storage protein of 17 kilodaltons. This 17-kilodalton protein was not disulfide-bonded to the 41 and 23-kilodalton complex. The first processing step was fast, the second slow: The half-lives of the precursors were about 3 and 10 hours, respectively. Finally, a group of 16- and 17-kilodalton proteins was synthesized by cleavage of large precursor proteins, likely in two steps. After cleavage, the proteins were not disulfide-bonded. The half-life of the precursors was short, less than 1 hour. In addition, for the 38-, 23-, and one of the 17-kilodalton proteins, a small decrease of relative molecular weight was observed as a last processing step. This was likely due to deglycosylation.     

Changes in protein synthesis during the development of Agrostemma githago seeds

The transition from the growth to the maturation phase in developing seeds of Agrostemma githago L. was found to coincide with major changes in the rate of protein synthesis, the kinds of proteins synthesized, and the composition of the non-proteinbound amino acid pool. Coincident changes were observed in viability and the ability to withstand desiccation. Desiccated mature Agrostemma seeds are dormant and need at least three months of after-ripening. In imbibed dormant and after-ripened seeds no synthesis of storage proteins was observed with the exception of one particular set of storage proteins. Dormant and after-ripened seeds synthesized the same kinds of proteins during early imbibition, indicating an almost identical metabolic state which differs considerably from that of developing seeds.     

Comparative Studies on Nitrate Reductase in Agrostemma githago Induced by Nitrate and Benzyladenine

NADH-nitrate reductase activity in excised embryos of Agrostemma githago develops in response to nitrate as well as benzyladenine. Induction of nitrate reductase by benzyladenine was much more susceptible to inhibition by a mixture of amino acid analogues and by cordycepin than induction by nitrate. In contrast, only induction of nitrate-nitrate reductase was decreased by chloramphenicol.     

温度和渗透胁迫对细叶鸦葱种子萌发的影响

多年生早春短命植物细叶鸦葱(Scorzonera pusilla)种子小而轻,吸水性强,非休眠。对其进行变温和渗透胁迫实验,结果为:细叶鸦葱种子的适宜萌发温度介于0~15℃,以4℃为最佳;变温对种子萌发无明显的促进作用。种子萌发率随PEG和NaCl溶液水势的降低而降低,与渗透胁迫程度呈负相关。而且,在渗透胁迫下,幼苗脯氨酸含量随胁迫程度的增强而增加。尽管温度不同,但是等渗的NaCl溶液对细叶鸦葱种子及其幼苗的胁迫程度大于PEG溶液,且表现出明显的离子毒害效应。结果对阐明荒漠区早春短命植物的生态地理格局及其干旱适应机制有着重要的理论意义。     

The Effects of Temperature and Osmotic Stress on the Germination of Scorzonera pusilla (Compositae) Seeds

Scorzonera pusilla is one of the early-spring short- lived perennial desert plants. Non-dormant seeds of S. pusilla are very small and light , and able to absorb water very quickly . Suitable temperature for germination was between 0℃ and 15℃, and the optimum temperature was 4℃ . With the increasing temperature, the germination percentage decreased evidently. Especially , temperature fluctuations had not significant effect on seed germination. Final germination percentages decreased distinctly with decreasing water potential of PEG and NaCl solution. The relationship between water potential of different solutions and germination was negative. The stronger the osmotic stress was, the more the proline content of seedlings was. The effects of NaCl on germination and seedlings were much stronger than that of iso-osmotic PEG in spite of two different temperatures, and the proline content of seedlings confronting increasing water stress was increased sharply .When the concentration of NaCl increased to some extent , the salt toxicity occurred besides water stress . The results are valuableto elucidate the ecogeographical patterns and mechanisms for adaptation of such early-spring ephemeral plants in the desert environments     

Inhibition of pregerminative processes in dormant and thermodormant Agrostemma githago seeds

Imbibed non-dormant seeds do not germinate immediately after completion of water uptake and reactivation of their metabolism. During the lag-period the seeds apparently undergo processes which are essential for germination. The extent to which these pregerminative processes occur in dormant seeds (freshly harvested seeds) and thermodormant seeds (afterripened seeds imbibed at a supra-optimal temperature) of Agrostemma githago was determined. The pregerminative processes were inhibited almost completely in dormant seeds, but only to 50% or less in thermodormant seeds. When seeds were progressing through the pregerminative processes, the axes showed a higher rate of protein synthesis than axes of blocked seeds. However, this increased rate of protein synthesis was a late event and neither necessary nor sufficient for germination.     

预浸和发芽过程中番茄种子细胞核的倍性变化

用细胞流检仪（ｆｌｏｗｃｙｔｏｍｅｔｅｒ）检测番茄种子细胞核倍性水平时发现：当年成熟的番茄种子胚细胞核ＤＮＡ绝大多数为２Ｃ水平,胚乳细胞核则为３Ｃ水平,说明成熟番茄种子细胞一般休止停留在Ｇ１期。同时我们也发现极少量的胚和胚乳细胞核分别为４Ｃ和６Ｃ水平,说明这些细胞已经进行了ＤＮＡ内复制。供试番茄种子浸种后１２ｈ左右完成吸水过程,２ｄ后胚根可突破种皮发芽。随着种子吸水过程的完成,胚根尖部分细胞开始进入ＤＮＡ复制期（Ｓ期）,而且此类细胞的数量增加迅速,一直到种子发芽。番茄胚根尖细胞进入４Ｃ的数量的多少与种子萌发时期有明显相关,４Ｃ／２Ｃ比率越大说明越接近发芽。渗控处理可以增加番茄种子胚根细胞４Ｃ／２Ｃ比率,因而明显提高种子的发芽速率。结果还表明;渗控处理的番茄种子再度干燥后４Ｃ／２Ｃ比率不变,这说明干燥可以固定细胞周期。     

一氧化氮对渗透胁迫下小麦种子萌发及其活性氧代谢的影响

一氧化氮供体硝普钠(Sodium nitroprusside,SNP)能明显地促进渗透胁迫下小麦(Triticum aestivum L.)种子萌发、胚根和胚芽伸长,提高萌发过程中淀粉酶和内肽酶的活力,加速贮藏物质的降解;胁迫解除后,仍能使种子维持较高的活力.此外,SNP还能显著诱导渗透胁迫下CAT、APX活力的上升和脯氨酸含量积累,抑制LOX活力,从而提高渗透胁迫下小麦种子萌发过程中抗氧化能力.进一步研究还发现,SNP诱导切胚半粒小麦种子萌发早期(6h)的淀粉酶活力上升可能与GA3无直接关系.     

一氧化氮对渗透胁迫下小麦种子萌发及其活性氧代谢的影响

一氧化氮供体硝普钠(Sodium nitroprusside,SNP)能明显地促进渗透胁迫下小麦(Triticum aestivum L.)种子萌发、胚根和胚芽伸长,提高萌发过程中淀粉酶和内肽酶的活力,加速贮藏物质的降解：胁迫解除后,仍能使种子维持较高的活力。此外,SNP还能显著诱导渗透胁迫下CAT、APX活力的上升和脯氨酸含量积累,抑制LOX活力,从而提高渗透胁迫下小麦种子萌发过程中抗氧化能力。进一步研究还发现,SNP诱导切胚半粒小麦种子萌发早期(6h)的淀粉酶活力上升可能与GA3无直接关系。     

Gibberellins and the photoperiodic control of stem elongation in the long-day plant Agrostemma githago L.

Agrostemma githago is a long-day rosette plant in which transfer from short days (SD) to long days (LD) results in rapid stem elongation, following a lag phase of 7–8 d. Application of gibberellin A₂₀ (GA₂₀) stimulated stem elongation in plants under SD, while 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride (AMO-1618, an inhibitor of GA biosynthesis) inhibited stem elongation in plants exposed to LD. This inhibition of stem elongation by AMO-1618 was overcome by simultaneous application of GA₂₀, indicating that GAs play a role in the photoperiodic control of stem elongation in this species. Endogenous GA-like substances were analyzed using reverse-phase high-performance liquid chromatography and the d-5 corn (Zea mays L.) assay. Three zones with GA-like activity were detected and designated, in order of decreasing polarity, as A, B, and C. A transient, 10-fold increase in the activity of zone B occurred after 8–10 LD, coincident with the transition from lag phase to the phase of rapid stem elongation. After 16 LD the activity in this zone had returned to a level similar to that under SD, even though the plants were elongating rapidly by this time. However, when AMO-1618 was applied to plants after 11 LD, there was a rapid reduction in the rate of stem elongation, indicating that continued GA biosynthesis was necessary following the transient increase in activity of zone B, if stem elongation was to continue under LD. It was concluded that control of stem elongation in A. githago involves more than a simple qualitative or quantitative change in the levels of endogenous GAs, and that photoperiodic induction alters both the sensitivity to GAs and the rate of turnover of endogenous GAs.Abbreviations AMO-1618 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride - GA(s) gibberellin(s) - LD long day(s) - LDP long-day plant(s) - SD short day(s)     

Protein Synthesis in Embryos of Dormant and Germinating Agrostemma githago L. seeds

The time course of protein synthesis in embryos of dormant and afterripened Agrostemma githago seeds was studied. In embryos of afterripened geminating seeds, protein synthesis increased in three successive stages: (a) concurrent with swelling; (b) during the lag phase between the completion of water uptake and the onset of growth; and (c) immediately after protrusion through the seed coat. Embryos of dormant seeds showed the first increase but not the second unless dormancy was broken by imbibition at 4°C. This indicates that dormancy affects processes prior to the onset of growth. The third increase was largely due to higher oxygen availability after the rupture of the seed coat and not to actual growth. It could also be elicited in dormant embryos by isolating them from the seeds.

Electrophoretic analysis of the newly synthesized proteins demonstrated that the patterns of dormant and afterripened embryos became significantly different in both axes and cotyledons only just prior to the onset of axis elongation. Thereafter, the differences became larger.

When afterripened or dormant seeds were transferred from a low, germination-permitting to a high, germination-inhibiting temperature, the seeds germinated at the high temperature if they had completed the lag phase to a sufficient extent at the low temperature. This shows that the processes during the lag phase were inhibited by the high temperature while the onset of growth was not affected.

     

光照对绒毛番龙眼种子萌发的影响

在实验室和自然条件下,研究了光照强度和光照时间对西双版纳季节雨林冠层树种绒毛番龙眼(Pometia tomentosa)种子萌发的影响.结果表明:不论是在持续光照还是在周期性光照条件下,3种不同强度光照处理的绒毛番龙眼种子萌发率都很高,均与对照(全黑暗)无显著差异;光照可加快种子萌发速度(降低萌发速率系数),提高萌发指数和幼苗活力指数.人工遮荫有利于绒毛番龙眼种子萌发率的提高,在100%自然全光照(natural sunlight, NS)下萌发率最低(27.8%),而在0.6% NS处理萌发率最高(78.9%);萌发速率系数在全光照下最大,随遮荫程度的增加而降低,萌发指数和幼苗活力指数则随遮荫程度的增加而增大.在遮荫萌发实验中,绒毛番龙眼种子的萌发可能主要受种子脱水敏感性的影响,即强光下剧烈的水分蒸发引起的暂时水分亏缺导致种子脱水死亡或萌发延迟;已经"萌发"的种子也可能因短期水分胁迫而不能生长到"第一对真叶出现"这一萌发标准就死亡,从而降低种子萌发率.在绒毛番龙眼种质资源保护工作中,既要注意避免强光下温度升高引起的种子过度脱水死亡,又要保证提供适宜光照条件以提高萌发质量和幼苗成活率.     

He-Ne激光和KT对小麦种子萌发与幼苗生长的影响

以冬小麦为实验材料,研究了单纯He-Ne激光处理、单纯激动素处理和He-Ne激光与激动素复合处理对小麦种子发芽率、生长势及叶绿素、可溶性蛋品质和可溶性糖合成的影响。结果表明：（1）三种处理均能提高种子的活力,促进种子萌发,相比之下He-Ne激光处理效果最好。（2）三种处理对幼苗生长、可溶性蛋白质、可溶性糖以及叶绿素的合成具有显著的促进作用,从而加快了光合作用的进程。提高了幼苗干物质的含量,其中He-Ne激光与激动素复合处理效果最好,单纯He-Ne激光处理效果次之。     

初生休眠解除状态和干燥处理对水曲柳种子萌发的影响

为探究初生休眠解除状态和干燥处理对水曲柳种子萌发的影响，本文以初生休眠的成熟水曲柳种子为材料，研究经不同裸层积（暖温10周+低温8周、暖温12周+低温8周、暖温10周+低温10周、暖温12周+低温10周）和干燥处理（干燥、不干燥）的水曲柳种子在适宜温度和较高温条件下的萌发表现。结果表明，初生休眠解除状态不同的水曲柳种子在不同温度下的萌发表现具有相似的规律，种子的萌发会受到干燥处理的影响。不经干燥处理的种子解除休眠越充分，其萌发能力就越强，但层积处理后的种子若经过干燥处理，则解除休眠越充分（尤其是低温时间越长），种子萌发能力下降越多。水曲柳种子次生休眠（热休眠）的诱导受种子初生休眠解除状态的影响较小，但受干燥处理影响较大。干燥处理会降低水曲柳种子的萌发能力，尤其是较高温条件下的萌发能力，初生休眠解除越充分的种子萌发受干燥处理影响越大。生产中如需对解除休眠的种子干燥处理，选择暖温10周+低温8周的层积方法处理种子效果最好。     

Induction of nitrate reductase by cytokinin and ethylene in Agrostemma githago L. embryos

In dark-grown, isolated embryos of Agrostemma githago, a transient period of nitrate-reductase (NR) (NADH: nitrate oxidoreductase, EC 1.6.6.1) activity occurred from 6 to 36 h after the start of imbibition. During this period, NR activity was enhanced by nitrate, 6-benzylamino-purine and ethylene. Ethylene and 6-benzylamino-purine acted synergistically, whereas ethylene had no effect on nitrate induction. Aminoethoxyvinyl-glycine, an inhibitor of ethylene biosynthesis, inhibited the cytokinin-induced increase of NR activity, but had no effect on the nitrate-induced increase. The inhibition by aminoethoxyvinylglycine was overcome completely by ethylene. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid had the same effect on NR activity as ethylene. Our data indicate that NR induction by cytokinins only occurs in the presence of ethylene, and that nitrate enhances NR activity through a mechanism which is distinct from the induction by hormones.Abbreviations ACC 1-aminocycloproparte-1-carboxylic acid - AVG aminoethoxyvinylglycine - BAP 6-benzylaminopurine - c.p. cotyledonary pair - NR nitrate reductase This article was finalized by the second author two weeks before his death. It was translated and adapted by Dr. G.J. de Klerk, Research School of Biological Sciences, Australian National University, Canberra. Reprint requests should be sent to Dr. de Klerk at his present address: Bulb Research Centre, Vennestraat 22, 2160 AB Lisse, The NetherlandsDeceased 4 September 1985     

Increase of protein synthesis after isolation in dormant and afterripened Agrostemma githago L. embryos

Isolated embryos are more suitable for in vivo study of protein synthesis than non-isolated embryos because, after isolation, the uptake of labeled amino acids is about 1000 times higher. However, isolation also stimulates protein synthesis: Up to 4 h after isolation, the capacity to incorporate labeled amino acids increased 7 times. Therefore, data on incorporation obtained with isolated embryos cannot be extended to non-isolated embryos. The increase of protein synthesis was not due to synthesis of specific proteins, but was a general increase. Furthermore, ripening, dormant, and afterripened embryos showed the same degree of increase. Isolation therefore stimulates protein synthesis nonspecifically. When embryos were kept under anaerobic conditions after isolation, protein synthesis did not increase. Therefore, higher oxygen consumption after removal of the seedcoat is probably the cause of the higher incorporation capacity. Furthermore, the activation of protein synthesis lagged several hours behind the increase of oxygen consumption.Abbreviations A afterripened - D dormant - pre-rRNA precursor of ribosomal RNA