Characteristics of rooting and early growth of transplanted rice nursling seedlings of different ages with different leaf numbers

摘要

The rooting and development of transplanted rice seedlings (Oryza sativa) are affected by seedling characteristics and the amount of damage to roots incurred by transplanting. Experiments were conducted to examine the influence of these factors on the rooting and early growth of transplanted rice nursling seedlings. To obtain seedlings with different plant ages in leaf number and seedling characteristics, seedlings were placed in a dark nursery chamber (32deg C) for 2 days, then raised for 3-7 days ina temperature-controlled greenhouse set at a dayight cycle of 24/19deg C under different seedling densities (200 g and 300 g per nursery box). The seedlings were continuously grown under the same temperature conditions after transplanting. The number ofroots at 8 days after transplanting was higher in seedlings with older plant ages compared with younger plants. However, transplanting injury, indicated by the rate of leaf emergence at 0-4 days after transplanting, was observed when the plant age of a transplanted seedling exceeded 2.6 in leaf number. This was primarily due to an imbalance between the total length of the leaf blade and that of the roots. This transplanting injury was aggravated at high plant density. It is suggested that seedling characteristics deteriorate when a plant exceeds an age of 2.6 in leaf number.