Grain Sorghum Root Responses to Water and Temperature during Reproductive Development
1986
Rice, J. R. | Eastin, J. D.
Yield reductions in grain sorghum [Sorghum bicolor (L.) Moench] are often traceable to suboptimal water or temperature conditions during reproductive development prior to anthesis. Root growth is rapid during this period of panicle development and could represent a competing sink that may influence seed number potential and grain yield. Root respiration in two grain sorghum hybrids (one stresstolerant and one normal) was monitored in hydroponic culture from panicle initiation through the hard-dough stage of grain development. Changes in total root respiration of the hybrids were approximately proportional to the respective changes in daily root dry matter accumulation. Rates of root respiration of both hybrids remained relatively constant from panicle initiation to boot stages, increased an average of 32% at the bloom stage, then declined to a minimum at the soft-dough stage. Root respiration of the normal hybrid was highest at the soft-dough stage and lowest at the hard-dough stage, while respiration in the stress-tolerant hybrid, whichas the greater stalk strength under late-season drought, was highest at the harddough stage. Higher metabolic activity of the stress-tolerant hybrid may be associated with its greater stalk strength under late-season drought. Response to temperature of root respiration for the hybrids was evaluated under control and water stress (-0.5 and -0.75 MPa) conditions during the boot stage. Under control conditions, root respiration of both hybrids increased about 40% with temperature increases from 25 to 30°C, however, no significant increases were detected with further temperature increases to 35 and 40°C.
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