Stages Of Microsporogenesis Research Articles

Histochemical studies on the cytoplasmic male-sterility of sugar beets, with special reference to the hydroeenion concentration, carbohydrates and amino acids in anthers.

The present paper is devoted to the observation of histochemical phenomena in anther tissue of cytoplasmic maie-sterile sugar beets contrasted with those in normal strains. I. Hydrogen-ion concentration in anther tissue. Based on several observations using pH indicators (Methyl red or Brom thymol blue), following conclusions could be drawn(Table 1, 2, 3 and Fig. 1, 2, 3). In the early stage of microsporogenesis, the pH values in anther tissue of both rnormal and malesterile types are rather high ranging: from 6.6 to 7.0. As the age of anthers of normal types advances to the microspore stage, the pH values decrease to about 6.2, then they increase agnin to about 6.8 at the D. ollen-grrain stage, and, at the anthesis, the pH values decrease to about 6.2. On the other hand, the pH values observed in anthers of male-sterile types never show such zig-zag curves as those of normal strains during the microsporogenesis, but gradually decrease to about 6.2 at the anthesis.

Developmental changes in the submicroscopic morphology of the cytoplasmic components during microsporogenesis in Tradescantia

The ultrastructure of the cytoplasm has been compared at various stages of microsporogenesis in Tradescantia paludosa in an effort to trace the development of the cytoplasmic organelles during the dividing phases of the pollen mother cells and during the differentiation of the pollen grain. It has been observed that the density of the cytoplasmic organelles reaches a maximum at the binucleate stage of the pollen grain, when mitochondria and Golgi bodies are found in abundance, along with small vesicles, endoplasmic reticulum, and some oblong bodies (possibly remnants of amyloplasts). The development of mitochondria has been traced from “promitochondria” which have poorly defined or no cristae. The “promitochondria” have been found to divide by “budding.” The text also deals with the formation and degeneration of Golgi bodies in the cells at different stages of development. Their formation is visualized as taking place through the coalescence of small vesicles; and degeneration is reflected in the reciprocal process of the breaking up of the organelles into small vesicles. The large plemorphic bodies in the prophase stages accumulate starch within lamellar structures and give rise to amyloplasts.

GROWTH AND PHOSPHORUS ACCUMULATION IN COTTON FLOWERS AS AFFECTED BY MEIOSIS AND FERTILIZATION

GROWTH AND PHOSPHORUS ACCUMULATION IN COTTON FLOWERS AS AFFECTED BY MEIOSIS AND FERTILIZATION

NUCLEAR DIVISIONS IN THE TAPETAL CELLS OF GALTONIA CANDICANS

The increasing number of descriptions of nuclear divisions in tapetal cells has established the fact that these divisions are mitotic rather than amitotic, as was previously considered by many to be the case. Strasburger (I882) described typical mitoses of tapetal nuclei. Duggar (I899) also early described mitoses in the tapetal cells of Bignonia venusta, which are normally binucleate during the stages of microsporogenesis following synizesis. Tischler (I906) described mitotic division of the nuclei in tapetal cells of Ribes. The second nuclear division, however, he found to be amitotic. He also found nuclei with the tetraploid chromosome number and concluded that such nuclei resulted from a fusion of the two diploid nuclei formed after the first division. Winkler (i906) described a fusion of nuclei in the tapetal cells of Wikstroemia indica. Mitotic divisions occur in the tapetal cells, resulting in a 2-6 nucleate condition. These nuclei usually fuse to form giant nuclei, but in some cases they remain separate. Tahara (I9IO) found in Morus indica that during the early stages of the heterotypic division the tapetal cells are binucleate. Their nuclei may fuse to form a single tetraploid nucleus which in turn may divide mitotically, or they may divide separately to form four nuclei. The four nuclei then fuse in pairs, so that each cell contains two tetraploid nuclei which may later divide mitotically. Bonnet (I912) made an extensive study of the tapetal cells in several genera of angiosperms and found mitosis to be the only method of nuclear division in the material examined. In Yu,cca the first tapetal nuclear division occurs before synizesis; in Fuchsia it occurs after synizesis. The second divisions are simultaneous in each cell. In some cases two of the spindle poles converge, so that during the telophases two of the four daughter nuclei fuse to form a single tetraploid nucleus. Thus the cell contains one tetraploid and two diploid nuclei. Bonnet also described a fusion of nuclei in a resting condition which results in the formation of tetraploid and octoploid nuclei. Gates and Rees (192I) found only mitotic nuclear divisions in the tapetal cells of Lactuca. The first division occurs at the start of synizetic contraction, and by the time of maximum synizetic contraction the tapetal cells are all binucleate. Some of them remain binucleate; others undergo a second nuclear division as the pollen mother cells reach the open spireme stage. The

A New and Rapid Method for Making Permanent Aceto-Carmin Smears

Smear the pollen mother cells of a single anther from each flower bud on a clean dry slide, using a small scalpel. Flood the slide with Belling's acetocarmin and heat for a second over an alcohol flame. Examine under the microscope to determine the stage of microsporogenesis. If the stage is satisfactory, smear the remaining anthers in the same manner, but fix and stain them by immediate immersion, face downward, in a petri dish full of hot (steaming) acetocarmin for from 1 to 10 minutes. Then rapidly transfer thru the following mixtures: two parts 99% (glacial) acetic acid plus one part absolute ethyl alcohol; one part acetic acid plus two parts absolute alcohol; and finally one part acetic acid plus nine parts absolute alcohol. The slides are then to be dehydrated completely by 1 to 2 minutes immersion in pure absolute alcohol, and cleared 2 to 3 minutes in a mixture of xylene and absolute alcohol in equal parts. The preparations are then made permanent by mounting each with balsam and a cover glass. Th...