Pollen Mother Cell Stage Research Articles

Relationship between pollen degeneration and amino acids, especially proline, in male-sterile Japanese radish ( Raphanus sativus L. var. longipinnatus Bailey)

Proline has been found to occur in only small quantities in sterile anthers, whereas it is abundant in fertile ones. However, the cause-and-effect relationship between proline and pollen degeneration was not clear. The present study was undertaken to solve this problem, using male-sterile and male-fertile plants of Japanese radish. The content of free amino acids in anthers of both plants was analyzed at the pollen mother cell (PMC) stage and at the mature (or degenerated) pollen stage. At the PMC stage there was little difference in proline content between sterile and fertile anthers, suggesting that proline is not involved in the condition of the anthers which leads to either sterility or fertility. At the mature (or degenerated) pollen stage, every amino acid occurred more abundantly in fertile anthers than in sterile ones. Fertile anthers at this stage contained much more proline than at the PMC stage. On the other hand, the quantities of amino acids in sterile anthers were small, and the decrease of proline was dramatic. These small amounts of amino acids, including proline, may be a result of pollen degeneration, because at this stage the collapse of pollen is so complete that only dried anther walls are anatomically observed. Filaments of sterile stamens contained much proline, suggesting its accumulation in situ due to the prevention of transfer to the destroyed anther.

MORPHOLOGICAL AND QUANTITATIVE CHANGES IN THE POPULATION OF CELL ORGANELLES DURING MICROSPOROGENESIS OF GASTERIA VERRUCOSA

The morphological changes in the nucleus and cell organelles of Gasteria during the development of the pollen mother cell into the ripe pollen are described and discussed. From the tetrad stage till after the first mitotic division the plastids contain electron transparent granules. The number of cristae in the mitochondria increases after the first mitotic division. When the pollen wall is formed the excretion of the Golgi vesicles' content and the contact of the plasma membrane with the callose wall determine the template of the pollen wall pattern. The formation of the material for the bacula, followed by that of the tectum, and finally by that for the footlayer, takes place on the plasma membrane. The excretion of the fine fibrillar content of the Golgi vesicles proceeds till after the formation of the footlayer. The excreted material remains between the bacula. The quantitative approach revealed that during meiosis the number of cell organelles remains constant. However, an increase in number takes place first after the pollen mother cell stage and before leptotene, secondly after the first mitotic division. The data are compared with the previous results obtained with Pinus sylvestris Willemse 1971a, b, c).

MORPHOGENESIS OF ISOLATED FLORAL BUDS OFRANUNCULUS SCELERATUSL. IN VITRO

SUMMARY Morphogenesis of floral buds excised at various stages of development was followed in vitro. The buds comprising the primordia of sepals and stamens (Stage I) failed to complete normal development on any of the nutrient media tried. However, the initiation and further development of carpels occurred even on a medium containing mineral elements, glycine, vitamins and sucrose. On the other hand, the buds having the anthers at the pollen mother cell stage (Stage II) completed microsporogenesis and 2-celled pollen grains were formed in the anthers. The torus i.e. the central dome bearing the carpels, of Stage II, and III (buds having anthers at pollen grain stage) elongated enormously and emerged through the folded sepals. Regeneration of roots and shoot buds (especially in Stage II & III buds) was common. In addition, the floral buds of all stages formed callus which subsequently differentiated roots, shoot buds and embryoids leading to the formation of plantlets. The latter, in turn, developed embryoids from the epidermal and pith cells of the stem. On subculturing, the hypocotyl portion of the in vitro plantlet was capable of developing embryoids directly from the epidermal cells, whereas the radicular and plumular portions of the same plantlet first formed callus and subsequently embryoids. The growth of callus and the differentiation of embryoids could be maintained through repeated subculturing. Embryoids could be induced even on a simple medium having only mineral elements and sucrose. Among the several growth adjuvants used, a combination of coconut milk and IAA supported best callus growth and normal embryoid differentiation.