DO PHYTOHORMONES INFLUENCE THE UPTAKE AND METABOLISM OF SUCROSE IN SPIKELETS OF WHEAT

ASTHIR B., KAUR A. & BASRA A. S. 1998. Do phytohormones influence the uptake and metabolism of sucrose in spikelets of wheat? Phyton (Horn, Austria) 38 (2): 293299. English with German summary. Effects of GA3, ABA and kinetin on C-sucrose uptake and invertase activity were studied in three cultivars of wheat (Triticum aestivum L.), namely HD 2329, PBW 343 and Kalyansona, using detached ears cultured in a liquid medium containing phytohormones for 6 h (short culturing) or 3 days (long-culturing). During long culturing, addition of GA3 and kinetin at 100 \xM increased the accumulation of free sugars in all the cultivars, but C-sucrose uptake and its conversion to starch was enhanced only in Kalyansona, suggesting differential hormonal responsiveness of the cultivars. Similarly, invertase activity especially that of neutral invertase was enhanced by GA3 and kinetin. ABA inhibited both sucrose uptake, starch and invertase activity in all the cultivars. These results suggest that gibberellin and cytokinin are positive modulators of grain sink activity, whereas ABA is a negative modulator. Hormonal stimulation of sink activity was reflected in increased dry matter accumulation and the starch content of grains.