Changes in ascorbic acid content during growth and development of Panicum miliaceum

Abstract

The present paper deals with changes in the ascorbic acid content of the shoot apex during its transformation from the vegetative to the reproductive state and its further development in Panicum miliaceum var. Samai Co. 1. Seedlings were exposed to 24-hour illumination, natural day, and 8 hours of illumination per day. Ascorbic acid was determined for the growing apex, stem, and leaf of the main shoot and for the individual branches produced on it at successive developmental stages. A several-fold increase in ascorbic acid content of the growing apex of the main shoot of plants grown under 8-hour illumination synchronizes with its transformation from the vegetative to the reproductive state. In plants grown under natural day and continuous illumination, which continue to grow vegetatively, the ascorbic acid content remains at a low level. Moving these plants to 8-hour illumination results in floral initiation and an increase in the ascorbic acid content. The high level of ascorbic acid is maintained through the gametogenic and embryogenic phases, but decreases during seed formation. A rise in ascorbic acid content of branch apices always occurs later than that in the main shoot but the increase again coincides with floral initiation in the branch apex. The ascorbic acid contents of stem and leaf are not significantly affected by the photoperiod. Hence, a massive upsurge in ascorbic acid content synchronizes with the transformation of the vegetative branch and shoot apices to the reproductive state.