Studies on Transplanting Injury in Rice Plant

I. The effects of root cutting treatments on the early growth of rice seedlings after transplanting

Abstract

This study was undertaken to clarify the effects of root cutting. Plots and experi mental procedures were shown in Table 1. Top and root growth observed during 4 weeks after treatments were summarized as follows:
1) Immediately after transplanting, leaf wilting was not observed in C-, 5 cm-and 3 cm-plot, but leaves were wilted in 1 cmplot and especially wilted in 0 cm-plot. And in these plots, leaf wilting recovered following the appearance of new roots about 3 days after transplanting, with slight death of the leaves (Fig.1). However, develop ment of tillers during the 1st week was very suppressed in all plots, whether the leaves were wilted or not (Fig.3B).
2) There were no significant differences in topand root growth between C-plot and 5 cm-plot or between C-plot and 3 cm-plot, except total leaf area and dry weight during the 1st to 2nd week after transplanting (Figs. 3 and 5). Moreover, it was note-worthy that 5 cm- and 3 cm-plot were superior compared with C-plot in plant height, root number and dry weight of top and root at the 4th week after transplanting (Table 2).
3) In 1 cm- and 0 cm-plot, the increase of tillers during the 2nd week after trans planting was fewer than C-plot. And so, top androot growth of these plots were signi ficantly inferior to C-plot over 4 weeks after transplanting (Figs. 3 and 5). Further, in comparison with the 1 cm-plot and 0 cm-plot, the plants in 1 cm-plot showed signi ficantly greater growth than the plants in 0 cm-plot. This indicates that the short remainnings of roots on the seedling at transplanting-time are very effective for the recovery from the transplanting injury.
4) During the 1st week after transplanting, dry matter distribution ratio to root was higher than any other time in all plots, and besides, higher in order of the strength of root cutting treatments (Fig.6). But, following the development of tillers, the ratios to leaf blade and/or leaf sheath and to stem increased. And so, the distribution ratio of dry matter to root decreased and the difference between treatments became little. As such a pattern of the distributions, percentages of each organ to whole plant and top/root ratio in dry weight was nearly equal in all plots at the 4th week after transplanting (Figs. 7 and 8).
5) From the above-mentioned results, it may be suggested that transplanting injury, mainly due to root cutting, will not occur if the seedlings have 3 cm or more roots in length.