S K Chakrabarty

Gibberellic acid in plant: Still a mystery unresolved

Gibberellic acid (GA), a plant hormone stimulating plant growth and development, is a tetracyclic di-terpenoid compound. GAs stimulate seed germination, trigger transitions from meristem to shoot growth, juvenile to adult leaf stage, vegetative to flowering, determines sex expression and grain development along with an interaction of different environmental factors viz., light, temperature and water. The major site of bioactive GA is stamens that influence male flower production and pedicel growth. However, this opens up the question of how female flowers regulate growth and development, since regulatory mechanisms/organs other than those in male flowers are mandatory. Although GAs are thought to act occasionally like paracrine signals do, it is still a mystery to understand the GA biosynthesis and its movement. It has not yet confirmed the appropriate site of bioactive GA in plants or which tissues targeted by bioactive GAs to initiate their action. Presently, it is a great challenge for scientific community to understand the appropriate mechanism of GA movement in plant’s growth, floral development, sex expression, grain development and seed germination. The appropriate elucidation of GA transport mechanism is essential for the survival of plant species and successful crop production.

Stigmatic receptivity determines the seed set in Indian mustard, rice and wheat crops

Stigmatic receptivity restricts the successful pollination in cereal crops. The present study deals with the biochemical test for enzymes producing in stigma of field crops such as Indian mustard, rice and wheat. The alcohol dehydrogenase and hydrogen peroxide assays revealed stigmatic receptivity as a violet color and oxygen bubbles released by the chemical reaction. Therefore, the 2 quick tests are in conformity to each other and supported the seed set data, which was utmost at blooming stage of flower ranged between 2–4 d All the 3 crops showed variation in stigmatic receptivity with respect to different time periods of blooming stages and hence, it may affects simultaneous pollen germination and tube growth, fertilization and seed set. The present finding suggests that the growth of pollen tube and stigma receptivity could be influenced by specific enzymes on stigma surface after 2–4 d of blooming stage, which contributes to proper seed set.

Pollen–pistil interaction in protogyny and self-incompatibility system of Indian mustard (Brassica juncea (L.) Coss.)

Abstract Fluorescence microscopic investigation was made to understand the interaction between developing pistils and pollen of protogynous (Pg) plants and between protogynous and non-protogynous, and cytoplasmic male sterile (CMS) plants following pollination in Brassica juncea. The pollen viability of protogynous plants was confirmed by staining with carmine acetic acid (CAA) and fluorescein diacetate (FDA). The entire process of intra-specific Pg × non-Pg post pollination events, starting from pollen deposition on the surface of the stigma and culminating with the entry of the pollen tube into the embryo sac, was rapid and completed within two days of pollination. Intra-specific crosses of Pg × Pg did not show a single pollen germination on the stigmatic surface and, consequently, no pollen tube growth was observed up to six days after pollination. The pattern of pollen tube growth in crosses between CMS × Pg was essentially similar to that for Pg × non-Pg pollination.