STUDIES ON TRANSPLANTING INJURY IN RICE PLANT .6. EFFECTS OF EARLINESS OF SEEDLING ESTABLISHMENT ON THE SUBSEQUENT GROWTH AND THE CHARACTERS RELATED TO YIELD

The leaf blades, top (leaf blade + leaf sheath), or roots of six-leaf-aged seedlings of medium maturing rice variety were pruned to various extent and transplanted in normal season to investigate the effects of earliness of seedling establishment due to the damaged part or extent of seedlings at transplanting on the subsequent growth and the characters related to yield. 1) The number of days required to first tiller appearance (DRFTA) might be used as an indicator of the length of establishment period of seedlings with varying damaged part of extent, since DRFTA was significantly and negatively correlated with the volume and activity of new roots at 7-8 days and with tiller number at 19 days after transplanting. 2) Seedlings with longer DRFTA had more main culm leaves and delayed flag leaf expansion or heading date. However, the extent of delay in growth stages was little as compared with that of difference in DRFTA since final leaf number and leaf emergence rate were significantly and positively correlated. Growth rate of seedlings with longer DRFTA was slow after transplanting, but quickly recovered after seedling establishment. And at the heading stage, the total dry weight and the leaf area of seedlings with all leaf blades or roots pruned were about 90% of control seedling. 3) DRFTA was negatively correlated with the maximum tiller number and the panicle number, but was positively correlated with the mean panicle weight. The relationship between DRFTA and panicle/straw weight ratio fluctuated among years because a climate considerably influenced DRFTA effects on straw weight. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.