THE ULTRASTRUCTURAL CYTOLOGY OF THE DIFFERENTIATING GUARD CELLS OF VIGNA SINENSIS

Structural differentiation of the guard cells of Vigna sinensis results from the integration of the following interrelated processes: a) intense activity of ribosomes, dictyosomes, endoplasmic reticulum (ER) membranes and mitochondria and patterned organization of microtubules; b) unequal thickening and ordered micellation of their walls and opening of the stomatal pore; and c) the divergent differentiation of the plastids. In differentiating guard cells, microtubules appear anticlinally oriented and more or less evenly distributed along the unthickened part of the dorsal wall and in the middle part of the ventral wall where thickening of the future pore occurs. In periclinal walls, microtubules fan away from the margins of the increasing thickening of the ventral wall and, later, from the rims of the stomatal pore towards the dorsal walls, parallel to the depositing radial microfibrils. Microtubules may be the cytoplasmic elements underlying guard-cell morphogenesis. Although cell-plate organization in guard-cell mother cells does not seem to differ from that of other protodermal cells, the middle lamella of the ventral wall becomes electron-translucent. The stomatal pore develops schizogenously from the internal and/or external ends of the ventral wall and proceeds inwards, remaining incomplete in most of the stomata of plants grown for 30 days in darkness and in some malformed ones which were developed after a prolonged action of colchicine. The guard cell, when approaching maturity, loses its organelle complexity and plasmodesmata, but it keeps a significant portion of its cytoplasm and organelles. Perigenous stomata generally exceed the size of mesoperigenous and mesogenous ones, develop large vacuoles and appear able to induce oriented divisions in their vicinity.     

CYTOLOGY OF BLUE-GREEN ALGAE. I. THE CELLS OF SYMPLOCA MUSCORUM

Pankratz , H. S., and C. C. Bowen . (Iowa State U., Ames.) Cytology of blue-green algae. I. The cells of Symploca muscorum . Amer. Jour. Bot. 50(4): 387–399. Illus. 1963.—The cellular morphology of Symploca muscorum is described, based upon electron micrographs utilizing improved techniques of specimen preparation. Except for a limiting plasma membrane, ribosomes, and Feulgen-positive chromatin, the cells have little resemblance to those of higher organisms. The longitudinal components of the cellular envelope consist of a 200–300 mμ fibrous sheath and a complex inner investment about 35 mμ thick which includes at least 3 distinctly layered wall elements in addition to the typical 7-mμ unit membrane forming the plasma membrane. A row of very small elongate “pores” pierce the inner investment on each side of, and immediately adjacent to, the junction of the longitudinal walls and the crosswalls. Crosswalls vary in thickness from 3 to 20 mμ, depending upon their age, and arise as elaborations of the inner layers of the longitudinal inner investment. The photosynthetic lamellar component of the cytoplasm consists of flattened sacs formed from unit membranes. The lamellae are concentrated in the peripheral region of the cell and usually are parallel to the longitudinal wall. These often extend from one crosswall to the next but, except for a few cases, are not continuous with the plasma membrane at either end. The Feulgen-positive nucleoplasm appears as an anastomosing system of lightstaining regions containing fibrils 2–5 mμ in diameter. The morphology and interrelationship of a number of other cellular elements are described: (1) structured granules range up to 0.5μ in diameter and occur near crosswalls; (2) polyhedral bodies, 0.2–0.5μ in diameter, are closely associated with the nucleoplasm; (3) “cylindrical bodies” characteristically consist of 2 concentric cylinders, are about 13 mμ in diameter and up to lμ in length; (4) “α granules” are spherical or somewhat elongate elements about 30 mμ in diameter and characteristically associated with the photosynthetic lamellae and structured granules; (5) “β granules” are spherical, highly osmiophilic granules which range from 30 to 90 mμ in diameter; (6) ribosomes, 10–15 mμ, in diameter, are most numerous near the nucleoplasm; (7) plasmodesms penetrate the crosswalls between adjacent cells. The cells of this organism can best be described as being in a “steady state” of division, and there is no evidence of any kind of organized distribution of the nucleoplasm to daughter cells during the constant progress of cytokinesis.     

眼结膜印迹细胞法及其影响因素

本文摸索眼结膜印迹细胞法及其影响因素,证明该方法是一项简便,快速,有效地评价机体维生素Ａ营养状况的方法;取样材料,染色时间,温度,透明方法均可影响制片结果。该方法适合基层推广应用。     

CYTOLOGY AND REPRODUCTIVE CHARACTERISTICS IN PENNISETUM SETACEUM

A green ecotype of fountaingrass, Pennisetum setaceum (Forsk.) Chiov., was found to be triploid (3x = 27) with 9 II + 9 I at metaphase I. Meiotic behavior of the bivalents was normal, but the univalents lagged and divided precociously at anaphase I. The univalent halves lagged at anaphase II and were distributed at random. Micronuclei were common, and stainable pollen was approximately 40%. The green type produced four progeny with 54 chromosomes. A purple strain of P. setaceum was found to be hexaploid (6x = 54) with varying chromosomal associations. Meiotic behavior was highly irregular and stainable pollen was almost zero. Megasporogenesis was initiated in both types, but the megaspores degenerated and nucellar and integument cells developed into four-nucleate, aposporous embryo sacs. Following self-pollination, the green type set approximately 10% seed and the purple type set 0.05% seed. Purple fountaingrass set as high as 18% seed following the application of pollen from Pennisetum ciliare (L.) Link (4x = 36), exemplifying a rare form of pseudogamy between two species. Improvement of P. setaceum through a standard breeding program appears unlikely.     

COMPARATIVE CYTOLOGY OF ULOTHRIX AND STIGEOCLONIUM1

This investigation describes the cytology of the ulotrichalean genera Ulothrix and Stigeoclonium. Cellular organization is similar to the degree that interphase cells of the 2 genera cannot be distinguished with certainly. In Stigeoclonium, the nuclear envelope becomes disrupted at the end of prophase, and centrioles enter the nucleoplasm. At metaphase the nuclear envelope is again intact, and some of the spindle tubules appear to be contiguous with the nuclear envelope. The spindle in Ulothrix is essentially open with, no attachment of spindle tubules to the nuclear envelope and with, centrioles on the spindle-cytoplasm interface at the spindle poles. Spindle poles are blunt in Stigeoclonium and pointed in Ulothrix. Cytokinesis is by cell plate formation in both genera, but there is no phragmoplast.     

THE DEVELOPMENT AND CYTOLOGY OF PYCNIDIOPHORA DISPERSA

Ascocarp development in Pycnidiophora dispersa is similar to that in Phaeotrichum. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layer differentiates to form the wall. The ascogenous system forms from a mass of fertile cells in the center of the centrum. These become enlarged and multinucleate and give rise to ascogenous hyphae which form asci at their tips by means of croziers. In time, most of the cells of the centrum become fertile and give rise to ascogenous hyphae. There are no sterile threads in the centrum and no hymenium is present, the asci being scattered throughout the locule. The haploid chromosome number is n = 6.     

THE MORPHOLOGY AND CYTOLOGY OF PREUSSIA FUNICULATA

The vegetative nuclei of Preussia funiculata (Preuss) Fuckel appear to divide in two ways. One is very similar to mitosis in higher plants except that no typical metaphase is present. The other consists of elongated nuclei splitting longitudinally into two halves. Ascocarp development is similar to that found in the Pleosporales. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layers differentiate to form the wall. The ascogenous system arises from multinucleate ascogonial cells scattered throughout the centrum. These give rise to large, lobate, multinucleate cells which in time form asci by means of croziers. The mature centrum contains a distinct hymenium and paraphysoids. The haploid chromosome number appears to be 12.     

TRISOMICS IN SOLANUM CHACOENSE: FERTILITY AND CYTOLOGY

Twenty trisomic plants found in the progeny 3x x 2x crosses in Solatium chacoense and their F₁ trisomies obtained by 2x + 1 X 2x crosses were studied with respect to their fertility and cytology. The female transmission of the extra chromosome in the trisomics varied from 2 to 60 %. The transmission frequencies of F₁ trisomies were similar to their parent trisomies in most of the lines. The transmission through the pollen ranged from 0 to 20 %. Female and male fertility of the parent trisomies was high. They produced an average of 37 seeds per pollination as the female or as the male parent. The F₁ trisomies produced about half the seed set of their parent trisomies. The extra chromosomes of six trisomies were identified by pachytene analysis. They were isochromosomes for the long arms of chromosomes I, IV and IX and the short arms of IV, IX and XII. Chromosome morphology of the extra chromosomes in pachytene stage was described. A chromosome association of 12 II + 1 I was found in 66 % of the cells at MI. About 29 % of the cells had one trivalent and 5 % had three or five univalents. The frequency of trivalent formation was not affected by the length of the extra chromosome. The possibility of univalent shift in secondary trisomies was discussed.     

处理方式不同的颗粒细胞和卵泡液对牛卵母细胞体外受精后卵裂率和囊胚率的影响

将牛的卵母细胞置于添加有不同预处理颗粒细胞及含有卵泡液的培养液或不舍有卵泡液的培养液中进行体外成熟、受精及胚胎发育培养,研究了颗粒细胞、卵泡液及颗粒细胞与卵泡液交互作用对牛卵母细胞成熟、受精后卵裂率、囊胚率的影响。2178枚卵母细胞体外成熟受精后胚胎发育的对比观察结果表明：颗粒细胞、卵泡液及颗粒细胞与卵泡液交互作用对卵母细胞成熟受精后胚胎的卵裂具有显著影响（P〈0．05）;颗粒细胞对囊胚的发育有显著影响（P〈0．05）;卵泡液及颗粒细胞与卵泡液交互作用对囊胚的发育无显著影响（P〉0．05）。不同因素对卵裂率、囊胚率的影响表现为：颗粒细胞因素〉培养液因素〉培养液×颗粒细胞交互作用。结论：TCM199培养液中添加卵泡液和单层颗粒细胞组成的培养系统用于牛卵母细胞体外成熟及胚胎发育的效果较好。共培养体系中的单层颗粒细胞用经酶消化分散处理后在培养箱中孵育10min的颗粒细胞替代时,胚胎的发育效果并不受影响。