ON THE DEVELOPMENT OF MACROSCLEREIDS IN SEED COATS OF PISUM SATIVUM L.

Macrosclereid differentiation was investigated by light and electron microscopy in pea testae during the transformation of protodermal precursors to the mature sclereids. The protodermal cells divide anticlinally and elongate into the macrosclereid layer during seed coat development. Young sclereids have elongate nuclei, plastids become somewhat granal during cellular maturation, vacuolation appears to be an autolytic process, and the cells have dense arrays of endoplasmic reticulum and ribosomes. Considerable dictyosome activity and microtubule development is observed as the secondary wall is produced. Many coated vesicles are associated with and fuse with the plasmalemma. During development, the outer tangential wall area of the macrosclereids acquires a definite cuticle and subcuticular layer. Also, at this time the sclereid walls under the subcuticular layer display semicircular microfibril orientation. The sclereid walls adjacent to the hypodermis become multilayered. As the macrosclereids near maturity, the “light line” becomes discernable in the light microscope at the junction of the cellulosic tips of the macrosclereids and the subcuticular layer. This “light line” is prominent using interference optics and is an osmiophilic layer in the electron microscope. This layer may represent the suberin “caps” reported by earlier workers.     

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。     

THE EFFECT OF CO2 ENRICHMENT ON ROOT NODULE DEVELOPMENT AND SYMBIOTIC N2 REDUCTION IN PISUM SATIVUM L.

A very significant increase in N₂(C₂H₂) reduction by Visum sativum L. infected with Rhizobium leguminosarum occurred when plants were grown in the light with 6 hr of CO₂ enrichment (0.00120 atm). Plants grown for 4 wk under 0.00120 atm CO₂ showed significant increases over control plants at 0.00032 atm CO₂ in plant dry weight, N content, root nodule mass, number of nodules, and mean nodule dry weight. Acetylene-reduction assays, however, revealed no reproducible increase in nitrogenase activity/mg nodule in plants subjected to long-term CO₂ enrichment. Both control and CO₂-enriched plants optimized the sink/source ratio between the mass of nodules and the extranodular plant mass. The optimum ratio for N₂ reduction by 4-week-old peas was 0.05. Long-term CO₂ enrichment did not promote root nodule formation to a greater degree than total plant development, and increases in N content were directly proportional to increases in nodule mass. Morphological data revealed significantly greater deposits of starch in root nodules of plants grown under CO₂-enriched conditions. The results are interpreted as showing that short-term increases in CO₂ levels promote N₂ reduction by affecting root nodule functioning, whereas long-term CO₂ enrichment promotes N₂ reduction by increasing total plant and root nodule development.     

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.