Abstract: Low temperature during vegetative stage would inhibit rice growth. It is still not clear whether such an inhibition is caused by direct action of low temperature or the result of prolonging growth period. Therefore, it is of great significance to answer this question for taking targeted measures to reduce damage induced by low temperature. Here, a water culture experiment was conducted with different low temperature durations (5, 10, 15 d at 15 ℃ and nitrogen application levels (40 and 80 mg·L^-1), to examine the changes of rice dry weight, nitrogen accumulation and growth period length. Results showed that low temperature inhibited the accumulation of dry weight and nitrogen. The longer low temperature lasted, the stronger impact it would have. When the temperature was recovered to normal level at the 10.5leaf age, the duration less than 5 d did not affect the growth period of rice, but theduration longer than 10 d delayed the growth period for 3-6 d. The dry matter weight could recover to normal level. Nitrogen application did not have significant effect on dry matter accumulation. When the duration was less than 5 d, nitrogen accumulation of the temperaturesensitive variety was 12.25% lower than that at the normal temperature, and nitrogen application could promote nitrogen uptake. However, the low temperature had limited effect on temperatureinsensitive varieties. Both the temperaturesensitive varieties and the insensitive ones could recover the nitrogen accumulation to normal level when the duration was longer than 10 d, and increased nitrogen application promoted nitrogen uptake significantly. Therefore, the effect of low temperature at vegetative stage on rice growth is mainly due to the delay of growth period. Resistant varieties with shorter growth period should be selected in practice, which has important significance in enhancing low temperature resistance of rice.

Key words: biodiversity, nodule, herbicide-resistant transgenic soybean, disease, weed, arthropod