The Ultracytochemical Localization of ATPase Activity in the Ovules of Antirrhinum majus L.

The ultracytochemical localization of ATPase activity was carried out by the method of lead precipitation in the ovules of Antirrhinum majus L. No ATPase activity is observed in the egg apparatus, but some in the polar nuclei, cytoplasm and plasma membrane of the central cell. Between the embryo sac wall and the cuticle surrounding it, there is a gap where some filamentand vesicle-like structures were demonstrated by conventional staining method, and much of ATPase activity is found there. At the chalaza of the ovule, a lot of ATPase particles are found irt the nuclei, plasma membranes and the thick and loose wall of the hypostase cells. The particles of ATPase in the hypostase and those in the gap surrounding embryo sac are continuously distributed through the intervals of the cuticle at the chalazal end of the embryo sac. Some of ATPase particles are found on the plasma membranes and plasmadesmata of integument ceils, noticeably much more in the nucleoplasm of the integumentary tapetum. According to the ATPase distribution pattern in the ovules, we suggest that the function of the integumentary tapetum and hypostase is secretion, and that the gap surrounding the embryo sac may be an apoplastic ehannal for nutrient flow into the embryo sac.     

芒苞草形态学和胚胎学研究：Ⅱ.花药和胚珠发育的研究

芒苞草成熟胚珠为倒生型,薄珠心,双珠被。胎座为侧膜胎座向中轴胎座的过渡类型。胚囊发育为单孢蓼型。 成熟胚囊由印器,具二极核的中央细胞及三个反足细胞组成。助细胞呈倒梨形,极性不明显,珠孔端壁有角状的丝状器。中央细胞的二极核在受精前融合为次生核。 花药具二个小孢子囊,花药壁层为单子叶型,具分泌型绒毡层,小孢子母细胞减数分裂时,胞质分裂为连续型,四分体是左右对称式排列,成熟花粉粒为二细胞的。 在花药与胚珠发育过程中,多糖物质的消长是有规律的变化。     

Competition both drives and impedes diversification in a model adaptive radiation

Competitors are known to be important in governing the outcome of evolutionary diversification during an adaptive radiation, but the precise mechanisms by which they exert their effects remain elusive. Using the model adaptive radiation of Pseudomonas fluorescens, we show experimentally that the effect of competition on diversification of a focal lineage depends on both the strength of competition and the ability of the competitors to diversify. We provide evidence that the extent of diversification in the absence of interspecific competitors depends on the strength of resource competition. We also show that the presence of competitors can actually increase diversity by increasing interspecific resource competition. Competitors that themselves are able to diversify prevent diversification of the focal lineage by removing otherwise available ecological opportunities. These results suggest that the progress of an adaptive radiation depends ultimately on the strength of resource competition, an effect that can be exaggerated or impeded by the presence of competitors.     

In vitro development of wheat (Triticum aestivum L.) from zygote to plant via ovule culture

Ovules of the wheat breeding line Veery #5 were excised and transferred to culture within 24 h after pollination. When ovules were cultured on Phytagel-solidified medium, and the pericarp removed exclusively at the micropylar tip and the abaxial side, zygotes from up to 79.2% of the ovules underwent embryogenesis with the same developmental pattern as found in planta. Embryos from more than 50% of the cultured ovules germinated when transferred to regeneration medium. More than 100 plantlets were randomly chosen for transfer to soil, all of which developed to phenotypically normal and fertile plants. With this system, the entire process of zygotic embryogenesis can be studied using living material. Furthermore, the method could be used as an embryo rescue technique for plant breeding purposes. Received: 17 June 1996 / Revision received: 22 October 1996 / Accepted: 15 December 1996     

云南鸡脚连(小檗科)的变异式样

小檗属鸡脚连(Berberis paraspecta Ahrendt)自1961 年发表以来,已有分类学文献对该种的描述一直模糊不清。通过在云南省玉龙县玉龙雪山野外调查与居群取样,结合模式标本核查,对鸡脚连重要分类学性状特征进行了补充和订正。鸡脚连果实1~5 个簇生,平均为(2.23±1.18)个;幼果或子房内胚珠1~3 个,平均为(2.07±0.29)个;成熟果实紫黑色,无粉霜,种子1~3 个,平均为(1.77±0.44)个。研究结果表明,有关文献关于鸡脚连果实单生,且仅含1 粒种子等关键的特征描述,在鸡脚连野生居群及模式标本上都不存在, 同时分析了鸡脚连果实、种子及胚珠数目、叶片及叶刺等分类学性状特征的变异系数,并补充了活植物及模式标本的图片资料。     

Diversification of seed arrangement induced by ovule rotation and septum formation in Leguminosae

The plants of Leguminosae, which comprises 731 genera, bear monocarpellary flowers. The fruit, known as a pod, generally contains a row of seeds, and the internal structure appears to be simple. In Leguminosae, the seeds are generally arranged longitudinally along the suture of the pod but, in a few genera, namely, Cassia, Indigofera, and Senna, they are arranged transversely. Transverse seed arrangement facilitates the accommodation of a considerable number of seeds and has been considered to be established by rotation of seeds during development. We studied the development both these patterns of seed arrangement, i.e., longitudinal and transverse, in Senna and Indigofera in order to elucidate the structural changes occurring in ovaries (or pods) and determine the forces responsible for rotation of ovules (or seeds) by dissecting ovaries and pods at different developmental stages. Our results showed that at an early developmental stage the ovules were obliquely oriented or transversely arranged; later, the direction of their growth was restricted by the ovary walls or neighboring ovules, and therefore the obliquely oriented ovules rotated inward or outward. Thus, it was clarified that the processes involved in the formation of the internal structure of pods are regulated in a complex manner. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Establishment of a simple and efficient system for somatic embryo induction via ovule culture in Arabidopsis thaliana

We established a simple and effective system to induce somatic embryos in Arabidopsis via ovule culture. Agar-solidified B5 basic medium supplemented with 10 μ M 2,4-dichlorophenoxyacetic acid was used for callus induction. Ovules at all developmental stages were tested, and among these, ovules older than 48 h after anthesis could be successfully induced to form embryogenic calli at high frequencies (42–82%). Structural and molecular probe analyses confirmed that the embryogenic calli were derived from embryos in the ovules. These calli were then easily induced to generate somatic embryos at frequencies of 63–95%. Subculture of the somatic embryos onto 1/2 strength MS medium resulted in their direct conversion into plants. The regenerants appeared morphologically normal and were fertile. This method provides a useful alternative tool to create sufficient numbers of somatic embryos for the study of biochemical and molecular mechanisms of embryogenesis, especially to recover early defective embryos in some mutations for cell-biological analyses.