797. BULBOPHYLLUM AMBROSIA

The epiphytic orchid Bulbophyllum ambrosia bears solitary, sweet‐smelling, nectariferous flowers that attract honeybees in considerable numbers, but it is self‐incompatible, making fruit‐set in the wild infrequent. Even so, the species is relatively abundant throughout its range in Asia. The species is described and illustrated and its taxonomic history, ecology and cultivation are discussed.     

940. BULBOPHYLLUM ANKYLOCHELE

Bulbophyllum ankylochele, a native of New Guinea, is illustrated. Its ecology and pollination are explained, and it is compared with the superficially similar Masdevallia from South America. Suggestions for its successful cultivation are given.     

中国石豆兰属新植物

植株很小,匍匐状。假鳞茎近圆形,粗约3-4毫米,彼此紧靠而生于匍匐的根状茎上,呈念珠状,顶生1叶。叶革质,卵状披针形或矩圆状舌形,长4-10毫米,宽2-3毫米,先端锐尖,基部收窄,无明显的柄。花葶从假鳞茎基部侧旁发出,1-2个,直立,纤细,圆柱形,高7-10毫米,顶生1朵花,基部被长约1毫米的筒状膜质鞘;花梗连同子房长约4毫米,比花苞片长,花苞片杯状,长约1毫米,先端锐尖,花红色,中曹片披针形或矩圆形,直立伸展,长5.5-7毫米,宽约1.8毫米,先端渐尖或锐尖,具3脉,侧萼片披针形,直立伸展,与中萼片近等长,宽约2毫米,先端长渐尖,具4-5脉,花瓣卵状矩圆形,长2.2毫米,宽1毫米,先端钝,具1脉,全缘,唇瓣披针形,长4毫米,中部以上下弯,先端增厚呈球状,且向下歪,基部具凹槽,与蕊柱足末端连合而形成不动的关节,唇盘平滑,蕊柱粗短,长约1毫米,蕊柱齿狭镰刀状,长约1.1毫米,蕊柱足长1.5毫米,向上弯曲,其游离部分长约7毫米;药帽半球形,表面平滑。     

ALLOZYME VARIATION IN OLD WORLD RACES OF SORGHUM BICOLOR (POACEAE)

A survey of allozyme variation in cultivated races of sorghum (Sorghum bicolor) was undertaken. Eight plants each of 83 accessions representing the five primary races and five of the intermediate races of sorghum were analyzed for 15 enzyme systems encoded by 27 loci. Low levels of variation were found within accessions, which is typical of self-pollinating species. Little variation was also found among accessions. Compared with other cereals, S. bicolor is depauperate in allozyme variation. We found an average of 1.81 alleles per locus with a mean expected heterozygosity of 0.008 for the accessions and total panmictic heterozygosity of 0.093. Only 9% of the variation present was found within accessions, while 91% was among accessions. Most of the variation present is attributable to differences in geographic origin of the accessions rather than racial differences. Western and eastern Africa have the highest levels of total heterozygosity (0.108 and 0.088, respectively), while southern Africa has the lowest (0.008). Principal component analysis revealed continuous variation among races and geographic regions with the accessions failing to segregate into discrete racial or geographic clusters.     

四倍体高粱与约翰逊草间的亲缘关系分析

本研究以四倍体高粱与约翰逊草为材料,利用SSR分子标记和细胞遗传学方法分析了高粱与约翰逊草间的亲缘关系,SSR分析结果表明,高粱与约翰逊草的遗传背景差异较大,SSR差异位点和相似位点在连锁群上的分布具不平衡性;按照差异引物出现频率高低,将连锁群分为两类：高度差异区和低度差异区。细胞学分析结果表明：（1）双亲及杂交种都是不规则的四倍体遗传群体。（2）花粉母细胞减数分裂中期I,双亲及杂交种染色体配对以二价体和四价体为主,杂交种平均每个细胞二价体数为17．00,四倍体高粱为15．23、约翰逊草为15．83,四价体数分别为0．95,2．15和1．60个。但杂交种减数分裂过程中也出现一定数量的单价体,减数分裂会形成一定比例的非整倍配子。SSR检测结果与细胞学分析结果具有一致性,约翰逊草与高粱的染色体组间存在一定程度的同源性。二者杂交不能形成稳定遗传的双二倍体。     

POLLEN PORE DEVELOPMENT AND ITS SPATIAL ORIENTATION DURING MICROSPOROGENESIS IN THE GRASS SORGHUM BICOLOR

The spatial relationships observed during microsporogenesis and pollen development in Sorghum bicolor indicate that a strong polarization exists in the anther locule and within individual microspores and pollen grains. During all developmental stages, each sporogenous cell and its derivatives lie continuously adjacent to the tapetum. The microspores and pollen grains form depressions in the tapetal orbicular wall. When the single pore of each microspore is initiated, as a gap in the primexine, it too lies adjacent to the tapetum and remains tightly appressed there until pollen maturity. A sequence of polar phenomena in microspores and pollen grains centers on an axis through the pore and perpendicular to the tapetal surface. These events include migrations of the microspore and vegetative nuclei, initial placement of the generative cell opposite the pore and its later migration, and a polar engorgement process whereby the pore end of the pollen grain (adjacent to the tapetum) fills with starch grains first. The tapetal cytoplasm completely degenerates at precisely the time of pollen engorgement, and its degradation products are believed to be available for pollen uptake at this time. The continuous association of the sporogenous cells or their cellular derivatives and their pores with the tapetum is thought to play an indispensible role in pollen development in sorghum and probably in all other grasses as well. The consistent position of the pore adjacent to the tapetum should be considered another common feature of microsporogenesis in the Gramineae. The characteristic exine pattern forms over the operculum and annulus of the pore, but the lamellae, which underlie the annulus, form a highly modified multilayered nexine. Membrane-like cores are observed in these lamellae and are believed to be involved in the initiation of sporopollenin deposition, but they are obliterated by pollen maturity. Neither the cores nor the lamellae are found in other parts of the pore or in the nonapertured wall.     

POLLEN WALL AND TAPETAL ORBICULAR WALL DEVELOPMENT IN SORGHUM BICOLOR (GRAMINEAE)

Pollen wall development in Sorghum bicolor is morphologically and temporally paralleled by the formation of a prominent orbicular wall on the inner tangential surface of the tapetum. In the late tetrad stage, a thin, nearly uniform primexine forms around each microspore (except at the pore site) beneath the intact callose; concurrently, small spherical bodies (pro-orbicules) appear between the undulate tapetal plasmalemma and the disappearing tapetal primary wall. Within the primexine, differentially staining loci appear, which only develop into young bacula as the callose disappears. Thus, microspore walls are devoid of a visible exine pattern when released from tetrads. Afterwards, sporopollenin accumulates simultaneously on the primexine and bacula, forming the exine, and on the pro-orbicules, forming orbicules. Channels develop in the tectum and nexine, and both layers thicken to complete the microspore exine. Channeled sporopollenin also accumulates on the orbicules. A prominent sporopollenin reticulum interconnects the individual orbicules to produce an orbicular wall; this wall persists even after the tapetal protoplasts degenerate and after anthesis. While the pollen grains become engorged with reserves, a thick intine, containing conspicuous cytoplasmic channels, forms beneath the exine. Fibrous material collects beneath the orbicular wall. The parallel development and morphological similarities between the tapetal and pollen walls are discussed.