PHOSPHORUS-NUTRITION AND WATER-STRESS TOLERANCE IN WHEAT PLANTS

The effect of phosphorus (P) nutrition and soil water availability (W) on the growth of wheat (Triticum aestivum L.) plants was studied in t wo pot experiments. Several levels of P supply were applied once befor e sowing. Before seedling establishment, the pots were kept near 100% of field capacity (FC). Afterwards, half of the pots were maintained b etween 60-70% FC. Control pots were kept at 85-95% FC by weighing and watering every two to three days. Several harvest of shoots were done before anthesis. At each harvest, dry matter and total P accumulation were measured in shoots. The main differences between both experiments were the way the drought stress was imposed, the levels of P supply, and the developmental stage of the plants at each harvest. In Experime nt 1, no additional P resulted in a reduction of the shoot dry matter of 24 and 48% for well watered and drought-stressed plants, respective ly. In Experiment 2, these reductions were of 33 and 65% for well-wate red and drought-stressed plants, respectively. In both experiments, th e effect of the drought-stress treatment was different at different le vels of P supply. Interactions between P and W treatments were attribu ted to both, a less intense drought stress in PO plants, and to the en hancement of drought-stress tolerance in P100 plants (Experiment 1), a nd P60 plants (Experiment 2).