RECENT DATA ON THE EFFECT OF SOWING TIME ON THE DEVELOPMENT OF LEAF-AREA AND YIELD IN WHEAT

Trends in the leaf area of three wheat varieties were studied as a function of sowing time in 1993 at Keszthely on Ramann's brown forest soil. The study was sponsored by OTKA fund 773102-134. The examinations were carried out on the following sowing dates: September 30, October 16, November 4 (factor A) and on wheat varieties GK Othalom, Mv 15, Yubileinaya 50 (factor B). The leaf area of samples taken every 10 days during the intensive leaf development period was measured by LI 3000 leaf area meter. Based on the results of the examination, the sowing time had a significant influence on the individual leaf area (LA), the size of flag leaf, the average value of leaf area index (LAI) and the integrated leaf area (LAD) of all three varieties. On the effect of later sowing date, the intensive development of assimilation area started later compared to that of plants with early sowing date, and the lagging was not balance even up to the end of the vegetation period. The foliage of plant stands sown at three different times finished its function at the same time. In all three varieties the same positive correlation was found between LAI, LAD, flag leaf area and the yield. By the first sampling (April 24), the differentiation of shott apex was slower in the third sowing time compared to the first and second sowing times. As the vegetation period progressed, the difference between the development of the generative organs disappeared.