Development and yield of spring wheat triticum aestivum cultivar solo in water culture as influenced nutrient concentration
Zeitschrift fuer Pflanzenernaehrung und Bodenkunde 142(6): 769-777
The development of spring wheat cv. Solo grown until maturity in nutrient solutions of normal concentration changed weekly, differs from similar plants growing in soil. In experiments in which nutrient supply was reduced at different growth stages, an attempt was made to minimize the differences. These consist mainly of permanent tillering, retarded senescing of leaves and in dry matter accumulation in the grain. Reducing the total nutrient supply during the grain filling period decreases the chlorophyll-content of the flag-leaf at an earlier stage and hence also its ability to assimilate CO2. This reduction in nutrient supply has a beneficial effect on the development of the grain by allowing a better coordination with leaf senescence and an increase in nitrogen and dry matter transfer from the flag leaf to the grain. The retarded response to a reduction of the nutrient concentration points to a luxury consumption in the vegetative phase. This might have prevented achievement of optimal timing of vegetative and generative development. After examination of the effect of lowering the nutrient supply in the vegetative phase, a nutritional design for growing spring wheat in water culture was proposed. This consists of lowering the concentration to meet the needs of plants and comprises a rise and fall of the concentration (0.25, 0.5, 0.75, 0.5 and 0.25 of the normal concentration). Comparing 0.4 and 0 mmol/l N during the grain filling (other nutrients supplied according to the concept outlined above), the relevance of N for the CO2-assimilation capacity and more obviously for the senescence of the flag leaf was shown. N deficiency decreases the assimilation ability within a short time and depresses grain development. These findings confirm the validity of the nutritional concept proposed.