ULTRASTRUCTURE OF THE SUBGLANDULAR CELLS FROM THE FOLIAR NECTARIES OF COTTON IN RELATION TO THE DISTRIBUTION OF PLASMODESMATA AND THE SYMPLASTIC TRANSPORT OF NECTAR

Foliar nectaries on the midveins of 7-cm leaves from cotton (Gossypium hirsutum L., cv. Stoneville 213) were examined by light and electron microscopy. The nectaries consist of external multicellular papillae and internal subglandular tissue that extends from the bases of the papillae to the vascular tissue of the midveins. The subglandular tissue is composed of small parenchyma cells; it does not contain sieve elements or xylem vessels. The parenchyma cells are rich in mitochondria, and their walls contain numerous pit fields having a high concentration of plasmodesmata. The absence of vascular tissue and the significance of the pit fields in the subglandular tissue are discussed in relation to symplastic transport of nectar secretions.     

STRUCTURE OF FLORAL NECTARIES OF ALFALFA (MEDICAGO SATIVA L.) IN RELATION TO NECTAR PRODUCTION

Alfalfa (Medicago sativa L.) plants differ in nectar volume production per floret. These differences are heritable, but no information is available on what type of structural variation may be responsible for these differences. One high, one intermediate, and one low nectar-volume-producing clone was selected from each of two alfalfa cultivars. Results from light and scanning electron microscopy indicated that alfalfa has an annular nectary located on the staminal column and primarily on the receptacle. It is composed of several cell layers subtended by vascular bundles containing both xylem and phloem. Vascular tissue does not extend into nectariferous tissue. Permanently open stomata are present in the epidermal layer and are thought to function in nectar secretion. These stomata did not respond to stimuli known to affect leaf stomata. Number of stomata per nectary among the six clones ranged from 24.7 ± 1.9 to 6.8 ± 0.5. Nectar-reservoir diameters among clones ranged from 1.07 ± 0.09 mm to 0.70 ± 0.01 mm. Clones producing the most nectar were characterized by a large nectar reservoir and moderate to high numbers of stomata.     

油菜花蜜腺发育过程的超微结构变化与泌蜜机理的研究

油菜花蜜腺由２枚侧蜜腺和２枝中蜜腺组成,其基本结构类似。在蜜腺发育过程中,产蜜组织细胞内的内质网、高尔基体、质体和线粒体以及液泡都发生有规律变化。泌蜜前,细胞器的数量增加。其中,质体内积累淀粉,此过程与蜜腺内初皮部的分化并和线粒体的增加相关。泌蜜时,内质网数量增多,并产生小泡．小泡向质膜移动。泌蜜后,细胞液泡化,细胞器数量减少,细胞萎缩。根据观察结果分析,其原蜜汁来源于韧皮部,转运至产蜜组织细胞的质体、内质网和高尔基体内加工成蜜汁,最后通过胞吐和渗透相结合的方式泌出。     

UDDER SIZE IN RELATION TO MILK SECRETION

The results herein presented furnish exact critical evidence for the conclusion that the most of the milk is present as such in the udder of dairy cattle at the time of milking. The amount of milk which may be secreted during milking cannot, on the basis of these results, be over 20 per cent of the milk yield of the cow. The results show clearly that the size of the udder measures closely the amount of milk which the cow is able to secrete. The results indicate that about 1/5 of a pound of secreting tissue is necessary for the secretion of a pound of milk during a period of 15 hours. The weight of the udder during the period that the cow is dry appears to be between 6 and 8 pounds.     

FLORAL NECTARIES AND TRICHOMES IN RELATION TO POLLINATION IN SOME SPECIES OF THEOBROMA AND HERRANIA (STERCULIACEAE)

Floral surfaces of two Theobroma spp. and one species of the allied genus Herrania (Sterculiaceae) were examined using scanning electron microscopy for reward system information of the pollinator-adaptation syndrome. These flowers are structurally complex and have sheltered reproductive parts indicating an elaborate insect-mediated pollination mechanism. Analysis of anther dehiscence, anthesis and pollen tube growth suggests a crepuscular pollination strategy. Suspected pollinators have been observed on floral parts of theobromas possessing stomate type nectaries and various shaped trichomes (blade of petal ligule and adaxial surface of petal hood). H. purpurea has elongate ligules devoid of stomates. Glandular clublike structures are found on the ovaries of all three spp. In numerous spp. of theobromas, except T. cacao, and two species of Herrania, a conspicuous ring of multicellular trichomes occurs at the adaxial base of the sepals. A possible function for the ring may be fragrance production because of its greatly reduced condition in the faintly scented T. cacao and the prevalence of pronounced fragrances in these other species.     

THE ULTRASTRUCTURE OF ADULT VERTEBRATE PERIPHERAL MYELINATED NERVE FIBERS IN RELATION TO MYELINOGENESIS

Adult chameleon myelinated peripheral nerve fibers have been studied with the electron microscope in thin sections. The outer lamella of the myelin sheath has been found to be connected as a double membrane to the surface of the Schwann cell. The inner lamella is connected as a similar double membrane with the double axon-Schwann membrane. The relations of these double connecting membranes suggest that the layered myelin structure is composed of a double membrane which is closely wound about the axon as a helix. These findings support the new theory of myelinogenesis proposed recently by Geren. The possible significance of these results with respect to cell surface membranes and cytoplasmic double membranes is discussed.     

锌对番茄叶绿体亚显微结构的影响与光强度的关系(简报)

番茄植物缺锌时,茎尖停止生长,叶部和茎上出现褐色斑点,有明显的小叶病症状。此外,叶绿素含量减少,光合强度降低,叶绿体结构遭到破坏。陈保生和崔澂发现叶绿体含锌量显著降低,并提出缺锌阻碍了叶绿体的发育。Hoagland发现锌在植物中的生理作用与光有关,此后,不少人对植物需锌与光的关系进行了研究,证明植物在光下较暗中需锌较多。通过进一步研究,李佳格和崔澂证明锌对自养生长的绿色植物的作用与光有关,而对异养的非绿色植物的作用与光无关。Spencer还报道锌和光影响叶绿体希尔反应活性。由此看来,锌与叶绿体的结构和功能是密切相关的。但锌在     

漆树乳汁道分泌细胞的超微结构及其与生漆产生和分泌关系的研究

漆树(Rhus verniciflua)乳汁道分泌细胞含有丰富的质体、内质网和嗜锇物质。电子显微镜的现察结果表明,嗜锇的生漆成分合成的可能场所是质体和内质网,并且通过内质网分子和小泡群与质膜相互接触并融合以及质膜内褶包被等三种形式释放到质膜和细胞壁之间的间隙中;再经过细胞壁中乳汁道腔形成时断裂了的胞间连丝通道和扩散渗透两条途径,越过细胞壁分泌到乳汁道腔中。细胞核、线粒体、高尔基体以及细胞质基质或多或少也参与了上述过程。     

白花罗勒(Ocimum basilium L.)盾状腺毛分泌过程的超微结构研究

白花罗勒成熟的盾状腺毛头部细胞中 ,质体含量丰富 ,体积较大 ,其中有大量的嗜锇物质积累 ;在分泌过程中 ,分泌细胞出现质壁分离现象 ;嗜锇物质向外分泌的途径有两条 :一条是以胞吐的方式 ,另一条是以渗透的方式     

北柴胡分泌道的超微结构及其挥发油分泌的研究

利用透射电子显微镜技术研究了北柴胡营养器官中分泌道的发育以及挥发油的积累.并重点探讨了挥发油的分泌机制.结果显示.分泌道细胞的质体、细胞基质以及线粒体参与挥发油或其前体物质的合成,而内质网参与挥发油向分泌道腔隙的转运.在分泌道发育的后期,大量小泡与分泌细胞相邻壁的质膜融合,并将其内的物质释放入此部分细胞壁中,与此同时,此部分壁在靠近腔隙的位置结构变得松散.然后围绕腔隙的壁在相邻两分泌细胞相接的位置面向腔隙外突形成许多小泡,并将小泡释放入腔隙中.由此可见.北柴胡分泌道中挥发油主要以胞吐方式被排入分泌道的腔隙中.     

旱生植物沙冬青和油蒿光合膜结构的超微分析

对比分析了沙冬青、油蒿的光合膜系统在人工补水条件与自然水分条件下的结构特点。结果表明,自然生长状态下的沙冬育与油蒿的光合膜系统均比人工补水条件下植株的简单,表现在基粒片层的叠垛程度降低,基粒片层与基质片层比率下降,其中自然水分条件下的沙冬育最明显。同时沙冬青叶绿体中能量型贮藏物质多于的油蒿。分析认为自然水分条件下植株光合膜的简单化可能是光系统Ⅰ、Ⅱ适应环境的表现;充足的水分保障了人工养护株发育出更为完善的光合膜系统。而沙冬育中多量的能量型贮藏物质与植株保持四季常绿有关。     

麝泌香盛期麝香腺超微结构和麝香分泌研究

雄麝特有的麝香腺,由于分泌行使化学通讯机能的信息素(Pheromone)麝香,结构特异。长期以来,国内外对麝香腺的结构和麝香分泌研究甚少,只有解剖学方面的简单描述,故对麝香分泌机理和泌香规律众说纷纭。我国最早(1958)进行过人工养麝和活体取香。随着养麝业的发展,近年对麝香腺进行了解剖、组织学(毕书增等,1980;冯文和等,1981;郑生武等,1984)和泌香机理研究(毕书增等,1980;李复东,1980;颜于宏等,1981),对麝香的分泌、形成与泌香规律有了进一步的认识,但缺乏全面系统的研究,特别在超微结构的研究方面尚属空白。     

STUDIES ON THE DEPLETION AND ACCUMULATION OF MICROVILLI AND CHANGES IN THE TUBULOVESICULAR COMPARTMENT OF MOUSE PARIETAL CELLS IN RELATION TO GASTRIC ACID SECRETION

Gastric parietal cells in mice present a spectrum of microscopic appearances due mainly to variations in the abundance of the tubular and vesicular component of the cytoplasm and in the size and number of microvilli lining the intracellular canaliculi. Differences in the range of forms among parietal cells of fasting versus fed mice were not especially striking, but cells with very numerous tubules and vesicles were more common after fasting. However, in mice treated with drugs or hormones that induce acid secretion, parietal cells were more uniform in appearance. There was a marked reduction of these cytoplasmic membranes and a concomitant increase in both the number and size of microvilli. Measurements of acid secretion in control animals and in animals treated with acid secretagogues indicated hydrogen ion secretion contemporaneous with depletion of the cytoplasmic tubulovesicular membranes and with increase of the microvilli. In mice with inhibited acid secretion, parietal cells showed an accumulation of cytoplasmic tubules and vesicles and reduction in the numbers of microvilli. Stereological methods were used to quantitate 10 different parietal cell compartments. Tracer studies with lanthanum did not reveal continuity between the tubules and the plasma membrane. However, there were regions of close apposition between the tubulovesicular membranes and the cell membrane of the canaliculus, and instances where cytoplasmic tubules extended from the cell into the core of enlarged microvilli.