DIFFERENTIAL EFFECT OF GA_3 AND ETHREL TREATMENT ON GROWTH AND SUCROSE CONTENT IN VARIETY CoSe92423

摘要

Sugarcane varieties (Saccharum spp. hybrids) that accumulate high levels of sucrose at the start of the harvest season are of considerable commercial interest. The sugarcane variety CoSe 92423 was exposed to a low concentration of the ethrel (50 ppm) and gibberellic acid (35 ppm) commencing from shoot emergence to increase plant extension rate. The changes in total carbohydrate % and plant growth were investigated. Results from experiments revealed a significantly higher amount sugar in their mother shoot and primary tiller after 6 months of growth in ethrel treated plants than GA. The treated plants had taller primary tillers with larger internodes, longer leaf lamina, and a low photosynthetic rate in GA treated plants but in Ethrel treated plants taller primary tillers with many smaller internodes, smaller leaves, and a higher (39%) photosynthetic rate was recorded. The three factors that may have contributed to the early accumulation of more sugar in the ethrel treated plants was: the specific leaf area of young leaves was greater (36%) than GA treated plants indicating efficient diversion of photo-assimilate to sink tissue, internode formation was initiated earlier, and internodes continued to form at a faster rate. Consequently, a greater proportion of the internodes in the ethrel treated sugarcane began filling with sucrose sooner than GA treatment. The higher reducing sugar level in the apical region of the plants probably contributed to faster internode development in both cases. This coincided with elevated acid invertase enzymes (27%) and sucrose synthetase activity (68%) in ethrel treatment which increased sucrose turnover in the parenchyma cells but in GA treated plants AI activity was high (57%) but sucrose synthetase activity (63%) was low. These findings extend our understanding of sugarcane variety which is able to accumulate a high level of sucrose early in the season through ethrel treatment.