GIBBERELLIN RELATIONSHIPS IN THE ‘ALASKA’ PEA (PISUM SATIVUM)

'Alaska’ peas (Pisum sativum L.) grown under a 16-hr photoperiod at 20 ± 1 C and an 8-hr dark period at 16 ± 1 C in their ontogeny exhibit two periods of sensitivity to applied gibberellin (GA), namely, prior to and subsequent to but not during the linear phase of stem elongation. This paper describes experiments conducted primarily with seedlings. Growth-saturating doses of GA, applied to dry seeds before planting (10⁻³ m) and to the shoot tips of 3-day-old seedlings (10 μg), evoked growth rates equal to the growth rate of etiolated seedlings. Sensitivity of seedlings to applied GA decreased with age through the first 2 to 3 weeks of development; by the time seedlings were about 14 days of age and had four elongating internodes they no longer responded to applied GA. As endogenous growth rate diminished late in ontogeny, the plants again became sensitive to applied GA. Growth response was used as a criterion for determining apparent translocation of applied GA. ‘Alaska’ pea seedlings appeared to transport GA, both acropetally from the cotyledons and basipetally from the shoot tip, to all internodes with remaining extension potential. Excision of both cotyledons at any time during the first 9 days of development caused a significant reduction of growth rate, and applied GA did not restore normal growth rate. No evidence was found that the cotyledons supply endogenous GA to the shoot axis in normal seedling development. It is suggested that the normal growth rate of light-grown ‘Alaska’ peas is correlated with the rate of synthesis of GA and that GA is rate-limiting for stem elongation during early seedling development and during the period of decreasing growth rate and onset of apex senescence.     

豌豆球蛋白及其亚基的分离提纯

本文详细地叙述了提取、分离、提纯豌豆球蛋白及其亚基的方法:用硼酸钠缓冲液提取豌豆球蛋白,用85%饱和度硫酸铵沉淀除去其它蛋白质杂质,再用凝胶柱进一步提纯;提纯的豌豆球蛋白通过DE_(52)-纤维素阴离子树脂柱(8M尿素作为变性分离试剂)和S_(200)凝胶柱(70%甲酸作为变性分离试剂)则可分离出豌豆球蛋白的各个亚基;试验结果还表明:在pH8.5时,33,000的亚基携带少量负电荷;而12,000的亚基携带大量负电荷。     

豌豆根瘤侵染细胞衰老过程的电镜观察

用透射电镜观察了豌豆根瘤侵染细胞在衰老过程中的超微结构变化,结果表明,侵染细胞和拟菌体的衰老有一定的规律和特征,首先是一些包裹拟菌体的包囊变得疏松,包囊和拟菌体之间出现较大间隙,间隙中常有一些纤维状和泡状物质。然后,细胞质失去正常结构,逐渐凝聚为染色很深的团块,进而完全泡状化,伴随着拟菌体的衰老,寄主细胞质染色由深变浅,细胞器逐渐减少,最后,液泡和质膜相继破裂,细胞完全瓦解,有时在衰老细胞的胞间隙,或在衰老的细胞质中有一定年轻的细菌,甚至在一片崩溃的拟菌体中还有侵染丝,有的还正在向寄主细胞质释放细菌。     

ANATOMY OF THE PRIMARY PHLOEM FIBER SYSTEM IN PISUM SATIVUM

Unusual structure of the primary phloem fiber system in the stem of Pisum sativum is described. The five lowest internodes contain large fiber strands that split radially and may also split tangentially. In both the stem and the root the number of fibers along a strand decreases with the distance below the leaf; in contrast, fiber length increases. Fiber dimensions are also increased in the centripetal direction.     

豌豆钙调蛋白基因的克隆及七种来源钙调蛋白基因的分析

从豌豆（Ｐｉｓｕｍ ｓａｔｉｖｕｍ Ｌ．）中提取总ＲＮＡ, 逆转录出ｃＤＮＡ 第一条链后, 以大麦钙调蛋白结构基因两端的寡聚核苷酸为引物, 用ＰＣＲ方法合成豌豆钙调蛋白基因, 克隆到Ｂｌｕｅ－ｓｃｒｉｐｔ 载体上并测定其全序列。结果与已知的苜蓿（Ｍｅｄｉｃａｇｏ ｓａｔｉｖａ Ｌ．）、水稻（Ｏｒｙｚａ ｓａｔｉｖａＬ．）、大麦（Ｈｏｒｄｅｕｍ ｖｕｌｇａｒｅ Ｌ．）、电鳗（Ｅｌｅｃｔｒｏｐｈｏｒｉｄａｅ）、根瘤（Ａｓｐｅｒｇｉｌｌｕｓ ｎｉｄｕｌａｎｓ）、酵母（Ｓａｃｃｈａｒｏｍｙｃｅｓｃｅｒｅｖｉｓｉａｅ） 钙调蛋白基因相比,同源性较高（９１．３％ —６０．８％ ）,其不同部分则常常是Ｃ和Ｔ相替换。进一步分析发现,上述七种来源的钙调蛋白基因之间,常有某些核苷酸替换方式占优势,它们对于氨基酸密码子的使用也各有偏爱     

豌豆细胞核仁中rDNA的超微定位和排布构型

利用细胞化学DNA特异染色法——NAMA-Ur特异染色法对豌豆细胞核仁中rDNA的位置及其排布构型进行了原位观察。结果表明,核仁中的rDNA位于纤维中心(FC)以及FC与致密纤维组分的交界处,以环绕FC的形式排布。不同位置的rDNA成分都具有集缩和解集缩两种形态结构,核仁外的核仁伴随染色质经过核仁通道进入核仁,沿FC周边排列,与其中的DNA相连。