EFFECTS OF TEMPORARY WATER-STRESS AFTER ANTHESIS ON GRAIN-YIELD AND YIELD COMPONENTS IN DIFFERENT TILLER CATEGORIES OF 2 SPRING WHEAT-VARIETIES

Water stress might limit grain yields of cereals under humid condition s. The objective of this study was to investigate the effect of a temp orary water shortage at three different stages after anthesis on the g rain yield and yield components of different tiller categories in two spring wheat varieties. A pot experiment with controlled water supply and rain shelters was conducted in 1984 and 1985 in Kiel, N.W. Germany . The water stress (pF 2.9 to 3.4) was imposed either between anthesis to early milk development of the caryopsis (WS1) (EC 65 to EC 72 acco rding to ZADOKS scale), early milk development to late milk developmen t of the caryopsis (WS2) (EC 72 to EC 77) and late milk development to maturity (WS3) (EC 77 to EC 92). The control had a constant water sup ply throughout the growing season of between pF 2.2 to 2.5. The water stress treatment WS1 significantly reduced the single plant yield by 1 0% (1984) and 15% (1985) in one variety (Selpek), whereas the other va riety was unaffected. The response of both varieties to the two later treatments was smaller and insignificant. In the first year the yield decrease in the variety Selpek after the WS1 treatment was mainly caus ed by a lower number of ears per plant compared with the untreated con trol (WS0). In the second year (1985) additionally a lower grain weigh t of the second category shoots caused by a reduction of the number of kernels per ear contributed to the decrease of the single plant yield . The yield component thousand grain weight could not compensate for t he reduction in the number of kernels per ear.