Studies on Transplanting Injury in Rice Plant

Abstract

Dried materials obtained in the experiment reported previously were used for analysis of nitrogen and total carbohydrate to see the effects of root cutting treatments on the contents of organic constituents of the rice seedlings after transplanting. And discussed the relationships between the organic constituents changes and the growth rate in the seedlings. The results obtained were summarizedas follows:1) In the 1 cm- and 0 cm-plot, leaves wilted immediately after transplanting, but their water contents recovered to near the same content as in C-plot at the 1st week after transplanting (Table 1).2) At the 1st week after transplanting, nitrogen concentrations of the top organs decreased in all plots. However, total carbohydrate concentrations of each organ, particularly in leaf sheath and stem increased, except 0 cm-plot (Fig.1). But, in general, there was no definite tendency in the effects caused by treatments during 2 weeks after transplanting. And, the concentrations of both constituents of each organ in 5 cm-and 3 cm-plot changed to near the same values as in C-plot, thereafter. On the other hand, in 1 cm- and especially in 0 cm-plot, nitrogen concentration, in particularly protein-N, was higher and total carbohydrate was lower than those in C-plot, because of nitrogen absorption rate increased linearly in these plots (Fig.3).3) Total nitrogen and carbohydrate accumulation of each organ changed in parallel with dry matter production in all plots (Fig.2). But, nitrogen accumulation rates in 1 cm- and 0 cm-plot were higher than dry matter production rate since the 2nd week after transplanting, compared with C-plot. Therefore, C/N ratio of whole plant became in order of C≅5 cm≅3 cm > 1 cm >0 cm-plot (Fig.4). These results indicate that the plants in 0 cm- and 1 cm-plot are physiologically more active than the ones in other plots after taking roots.4) RGR during the 1st week after transplanting was lower in order of the strength of root cutting treatments, mainly due to the difference of NAR by the degree of leaf wilting (Fig.5). However, it was noteworthy that RGRs in 5 cm- and 3 cm-plot changed near the same values as C-plot, on the other hand, RGRs in 1 cm- and 0 cm-plot were higher than those in other plots since the 3rd week after transplanting. It was suggested that these results were brought by the differences in NAR and RLGR but not in LAR, due to the difference of nitrogen concentration in the whole plant. And RGR showed close correlations with NAR and RLGR (Fig.6).5) From the above- mentioned results, it was concluded that there was no dif ference between the normal seedlings and the ones having 3 cm or more roots in length, because both were almost the same in contents of organic constituents and RGR during 4 weeks after transplanting.