Effect of foliar application of triacontanol on growth and yield of rice plants. II. Effect of the triacontanol concentration.

Abstract

In the previous paper it was reported that the yield of rice was increased by the foliar application of triacontanol (TRIA) at early growth stages. However, as the range of TRIA concentration used was not so wide, the effect of concentration was examined in this report. Main results obtained are as follows: 1. The range of effective concentration was found to be wide, from 0.2 to 10ppb, and the highest yield, 16% over the control, was obtained by 10 ppb sprayed at the early tillering stage. 2. By TRIA-spraying, growth of the top was slightly inhibited, but the root system during the ripening period remained considerably heavier than the non-treated control. 3. In most cases, yield increase was brought about by increases in the percentage of ripened grains and in 1000-grain weight. 4. Both the dry weight increase and NAR during the ripening period were higher in the TRIA-treated plots than in the control plot. A high, positive correlation was found between these two growth parameters. From these results it was inferred that TRIA-application increased the number of panicles and grains and, in addition, helped maintain a large and healthy root system during the grain-filling period, which contributed to promoting ripening by increasing dry matter production after heading.