Gibberellin Structure-Dependent Interaction between Gibberellins and Deoxygibberellin C in the Growth of Dwarf Maize Seedlings

The effects of 3-deoxygibberellin C (DGC) on the growth-promoting actions of gibberellins A₁, A₂, A₃, A₄, A₅, A₇, A₈, A₉, A₁₃, A₁₈, A₁₉, A₂₀, and A₂₃ (GAn) as well as 13-deoxygibberellin A₅ (deoxy-GA₅) were tested with seedlings of gibberellin-deficient dwarf mutants (d₂ and d₅) of maize (Zea mays L.). It was found that DGC promoted the actions of gibberellins having both C-1 double bond and C-3 axial hydroxyl group, and it inhibited the action of gibberellins having the saturated ring A and lacking the C-3 axial hydroxyl group, whereas it did not affect that of the ones having the hydroxyl group. The presence of C-2 double bond, as in GA₅ and deoxy-GA₅, diminished the inhibitory action of DGC. The DGC inhibition was alleviated by raising the doses of the relevant GAs, suggesting that it is a competitive inhibition. These results and the finding that the growth of normal maize and rice seedlings are inhibited by DGC indicate that GA₉, GA₁₉, GA₂₀ or other gibberellins having ring A of the same structure are involved in the growth of these plants as active form(s) or as intermediate(s) leading to the active form(s).     

Gibberellins and Heterosis in Maize : II. Response to Gibberellic Acid and Metabolism of [H]Gibberellin A(20)

Two maize inbreds, CM7 and CM49, and CM7 × CM49, their F₁ hybrid (which displayed significant heterosis), were examined with regard to response to exogenous gibberellin A₃ (GA₃), and in their ability to metabolize GA₂₀, a native GA of maize. The leaf sheath elongation response to GA₃ was far greater for the imbreds than for their hybrid. The inbreds also displayed significant elongation of the leaf blades in response to GA₃, whereas the hybrid was unaffected. Promotion of cell division in the leaf sheath of CM7 and the hybrid was effected by GA₃, but no promotion of cell elongation was observed in CM49, even though significant leaf sheath elongation occurred. Shoot dry weight of both inbreds was significantly increased by GA₃, but response by the hybrid in this parameter was slight and variable. Root dry weight of CM7 was significantly increased by GA₃, but was unchanged in CM49 and the hybrid. Thus, inbred shoot dry weight increases effected by GA₃ were not at the expense of the root system. Rapid metabolism of [2,3-³H]GA₂₀ occurred in all genotypes, although genotypic differences were observed. The hybrid had the highest rates of metabolism to GA glucosyl conjugate-like substances. Oxidative metabolism was also fastest in the hybrid, followed by CM7, and slowest in CM49, the slowest-growing inbred. Thus, rate of GA₂₀ metabolism is under genetic control in normal (i.e. not dwarfed) maize genotypes. These results, taken together with previous reports that the hybrid has significantly enhanced levels of endogenous GA-like substances, suggest that GA play a role in the expression of heterosis in maize.     

Extractable and Diffusible Gibberellins From Light- and Dark-grown Pea Seedlings

Gibberellins were obtained from light- and dark-grown peas by solvent extraction and agar diffusion. Both A₅- and A₁-like gibberellins were obtained by extraction; however, by diffusion only the A₁-like gibberellin was found. There was no significant quantitative difference in the levels of diffusible or extractable gibberellin obtained from light- and dark-grown tall and dwarf peas. Several possible explanations for the discrepancy between diffusible and extractable gibberellin were investigated. Of these, only I was supported by experimental evidence, namely, that GA₅ can be converted to GA₁.     

The Occurrence and Development of Amylase Enzymes in Incubated, De-embryonated Maize Kernels

The development of amylase activity in extracts from de-embryonated and GA₃-treated de-embryonated maize kernels (Zea mays L.) was determined during a 10-day incubation period. The increase in activity was compared with activity extracted from endosperms dissected from germinating whole kernels. Chromatographic analysis of reaction products as well as physicochemical characterization demonstrated that the activities from GA₃-treated and nontreated tissue were comparable and that part of the activity was attributable to α-amylase.     

玉米杂种优势分子基础研究进展

当今作物改良中杂种优势的广泛应用得益于杂交玉米的首先培育成功,对其分子基础的探讨已历经近一个世纪却尚未达成共识。关于杂种优势的经典解释曾聚焦于显性和超显性假说,现在看来似乎是借喻遗传学分子概念而无实际分子基础的实用性概念,籍此导致了一些研究结果的不一致是可以理解的。随着基因组时代的到来和相关分子技术的出现,文章回顾了过去的研究结果,分析了杂种优势分子机制研究的现状和问题,针对两亲本及其后代杂交后基因组构架和基因表达变化的研究趋势及方向进行了评价,并提出了由此资讯引发的SNPs单倍型用于玉米杂种优势分子基础研究的新策略。     

蛋白质组学技术在玉米杂种优势研究上的应用进展

杂种优势是生物界普遍存在的一种现象,在玉米中已经广泛应用,但其形成的分子机理仍不清楚。蛋白质组学技术是一种高通量筛选重要功能蛋白的研究手段,在玉米杂种优势的形成上进行蛋白质组学研究有利于深入解析杂种优势形成的分子机制。简单介绍了玉米杂种优势的表现,并对玉米种子胚、苗期根系、叶片和雌穗等性状上有关杂种优势形成的分子机理的蛋白质组学研究进行了综述。     

Metabolism and Translocation of Gibberellins in the Seedlings of Pharbitis nil (II). Photoperiodic Effects on Metabolism and Translocation of Gibberellins Applied to Cotyledons

We investigated the metabolism and translocation of two gibberellins(GAs), [³H]GA₂₀ and [³H]GA₁, which were applied at low concentrationto the cotyledons of Pharbitis nil (cv. Violet). Seedlings weregrown under three different photoperiodic conditions: continuouslight (CL-CL), continous light followed by short day conditions(CL-DT) and long day conditions followed by short day conditions(DT-DT). Translocation of the applied [³H]GAs from cotyledonsto hypocotyls was promoted by DT for all GAs examined. Whilethe conversion of the translocated [³H]GA₁ to [³H]GA₈ and itsconjugates was rapid in hypocotyl, the conversion of translocated[³H]GA₂₀ to [³H]GA₂₉ was slow. Radioactivity in epicotyls wasdetected much more rapidly on application of [³H]GA₂₀ than of[³H]GA₁, [³H]GA₈ and [³H]GA₂₉ and their conjugates. The conversionof [³H]GA₂₀ to [³H]GA₁ in the epicotyl was more rapid underCL-CL conditions. This result in consistent with the higherlevel of endogenous GA₁ existing in epicotyls under CL-DT thanDT-DT conditions. However, when [³H]GA₁ was applied to the cotyledon,only small amounts of [³H]GA₈ and its conjugates were detectedin the epicotyl regardless of the photoperiodic conditions.This result may suggest that the translocation and metabolismof [³H]GA₂₀ from cotyledons to epicotyl was faster under CL-CLthan DT-DT conditions and may correlate with the increased epicotylelongation of GA₂₀ treated plants under CL-DT than DT-DT conditions. (Received June 28, 1995; Accepted November 2, 1995)     

Isozyme Studies in Predicting the Potential Yield of Heterosis in Maize

Electrophoretic isozyme zymogram patterns of peroxidase (POD), cytochrome oxidase (COD), esterase (Est), α-amylase (α-Amy), catalase (Cat), Glutamate dehydrogenase (GDH), Malate dehydrogenase (MDH), superoxide dismutase (SOD), acid phosphatase (Acp), etc. obtained from 108 maize inbred lines and their 199 hybrids were analyzed. The soluble protein patterns from these materials were tested as well. The authors had probed into the relationship between the index of zymogram difference and potential yield of heterosis in maize. The results indicated that hybrids from parents which showed high zymogram difference index could produce high heterosis and those from parents which had low zymogram difference index could also produce high heterosis as well. But hybrids from the sister lines which had lower zymogram difference index could only produce lower heterosis. There was no significant statistical difference between isozyme zymogram difference index and potential yield of heteroSis on a genetic background with complex combinaton.     

Phenotypic Plasticity Contributes to Maize Adaptation and Heterosis

Plant phenotypic plasticity describes altered phenotypic performance of an individual when grown in different environments. Exploring genetic architecture underlying plant plasticity variation may help mitigate the detrimental effects of a rapidly changing climate on agriculture, but little research has been done in this area to date. In the present study, we established a population of 976 maize F₁ hybrids by crossing 488 diverse inbred lines with two elite testers. Genome-wide association study identified hundreds of quantitative trait loci associated with phenotypic plasticity variation across diverse F₁ hybrids, the majority of which contributed very little variance, in accordance with the polygenic nature of these traits. We identified several quantitative trait locus regions that may have been selected during the tropical-temperate adaptation process. We also observed heterosis in terms of phenotypic plasticity, in addition to the traditional genetic value differences measured between hybrid and inbred lines, and the pattern of which was affected by genetic background. Our results demonstrate a landscape of phenotypic plasticity in maize, which will aid in the understanding of its genetic architecture, its contribution to adaptation and heterosis, and how it may be exploited for future maize breeding in a rapidly changing environment.     

三个玉米合成群体选系的配合力及杂种优势分析

采用NCⅡ遗传交配设计,通过在黑龙江省哈尔滨和泰来的两点试验,以玉米自交系Mo17、B73、444和丹340为测验种,对从群体品综1号、中综3号和陕综5号选育的18份自交系进行配合力及杂种优势分析,以探讨群体选系在我国东北早熟玉米区的利用途径。结果表明,供试自交系间一般配合力存在较大差异;陕综5号群体选系HR14、HR17和HR15、中综3号选系HR9和HR8、品综1号选系HR4的一般配合力较高。在供试的72个组合中HR15×丹340、HR17×丹340、HR9×Mo17、HR14×丹340、HR7×B73、HR8×B73、HR6×444、HR5×丹340产量的特殊配合力及对照优势较高,表现出较高的利用潜力。依据特殊配合力及对照优势分析,中综3号选系与旅大红骨群、陕综5号选系与兰卡斯特群、品综1号选系与瑞德群遗传关系较近。结合育种实践,在我国北方早熟春玉米区陕综5号×旅大红骨、中综3号×瑞德或兰卡斯特、品综1号×旅大红骨或唐四平头可能组成较大利用潜力的杂种优势模式。     

水稻和玉米幼苗的超弱生物光子发射比较研究

利用自制的超高灵敏度超弱生物光子发射（ultraweak biphoton emissions,UBE)二维图象系统观测比较了水稻（Orza sativaL.)和玉米（Zea maysL.)不同品种种子萌发过程中超弱生物光子发射的变化。发现普通饲料玉米（阳单82）和高杆水稻品种（金科占）的种苗及＋1叶的UBE分别比超甜玉米品种（穗甜1号、3号）和矮杆水稻品种（矮珍占）低,而前者的UBE衰减比后者要快,进一步证实超弱生物光子发射是十分灵敏的,且其差别的出现远远早于其它生物学指标,这种特性可能具有普遍性。     

赤霉素对水平放置水曲柳幼苗的负向重性和木材形成的影响

对水平放置2年生水曲柳(Franxinus mandshurica)幼苗应用赤霉素(GAs)及其合成抑制剂烯効唑(Uni．-P)对幼苗的负向重性及木材形成中的生理作用进行了探讨。每种生长调节物质100μg溶于50％的丙酮中，每周1次处理于幼苗顶端，连续处理5周，并在第1次处理后24h，将幼苗水平放置。在实验期间，对照及GAs处理幼苗茎负向重性受到了促进，而Uni．-P处理则受到了抑制。GAs增加了茎上侧具有增厚细胞壁的胶质纤维细胞的数量。Uni．-P抑制了茎上侧的木材形成，但没有影响胶质纤维的分化。对照区木质部中纤维素与木质素的比值上侧大于下侧。该比值在上侧GA4处理区大于GA3处理区及对照区。该结果说明，胶质纤维的分化和木质部的增加对负向重性都是重要的；在该种中，赤霉素对于木质部细胞形成可能比对胶质纤维分化的影响更大。     

玉米黄化幼苗生理生化特性的研究

以玉米品种'户单26'为材料,研究了黑暗条件下生长的玉米黄化幼苗内光合色素、可溶性蛋白含量和抗氧化酶活性的动态变化.结果表明,与正常条件下生长的对照组相比,黄化幼苗的叶绿素a、叶绿素b和类胡萝卜素含量均明显降低,特别是叶绿素a含量大幅度降低;黄化幼苗的抗氧化酶SOD、POD和CAT活性显著提高,可溶性蛋白含量也显著增加.研究发现,黑暗条件下的玉米幼苗叶绿素a的合成受到了显著影响而表现出黄化现象,黄化幼苗能主动提高其自身抗氧化酶活性和可溶性蛋白含量,减轻黑暗逆境对植物细胞的伤害.     

AFLP标记与玉米杂种产量,产量杂种优势的预测

以１７个玉米（Ｚｅａ ｍａｙｓ Ｌ．）自交系及其按双列杂效配制的１３６个单交种为材料,研究ＡＦＬＰ分子标记与玉米杂效种产量、产量杂种优势的关系。结果表明,基于ＡＦＬＰ数据计算的遗传距离与１９９７年杂种产量、产量中优势的相关系数（ｒ）分别为０．４５０３、０．３７１４,与１９９８年杂种产量、产量杂种优势的相关系数分别为０．４３５２、０．３２５３,均达到显水平,但决定系数（ｒ＾２）都很小。当亲本材料改