[Effect of hyacinth mulching on rice (Oryza sativa L.) uptake and utilization of nitrogen].

Nitrogen is the most important element for rice growth, and hyacinth can absorb large quantities of nitrogen and accumulate in their tissues. The field experiment was conducted to investigate the effects of hyacinth mulching on rice nitrogen (N) concentration, uptake, efficiency and allocation at different growth stages. Taked Yun 2645 as a material, the nitrogen uptake and utilization of rice were evaluated under two different levels of N input: low (LN, 120 kg x hm(-2)) and normal N (NN, 240 kg x hm(-2)) in 2009. Main results showed that: (1) Compared with AMB, hyacinth mulching significantly increased N concentration in rice plant over the season, hyacinth mulching significantly increased nitrogen accumulation in rice plant, and the increasing rate was gradual addition from mid-tillering to heading, but from heading to maturity the increasing rate was gradual decline. (2) Hyacinth mulching had no obvious effect on nitrogen allocation pattern in leaves and stems of rice over the season, significantly decreased nitrogen allocation pattern in spikes. (3) Except mid-tillering, hyacinth mulching resulted in the significant decrease in N use efficiency for biomass (NUEp) over the season and in N use efficiency for grain yield (NUEg) at grain maturity, but no effect was observed on nitrogen harvest index (NHI). (4) Nitrogen concentration and accumulation at most growth stages of rice increased with increasing N supply (p < 0.05 or 0.01), but NUEp and NUEg showed the opposite trends. 1(5) nteractions between hyacinth mulching x N were not observed for N uptake and utilization. Hyacinth mulching increased N concentration and N uptake, decreased NUEp and NUEg at most growth stages of rice.

[Effects of high temperature on grain filling and some physiological characteristic in flag leaves of hybrid rice].

The effects of high temperature on grain filling rate and some physiological indexes in flag leaves in hybrid rice Teyou 559 were studied. The results showed that chlorophyll content and superoxide dismutase (SOD) activity in flag leaves were lower significantly by high temperature stress (Figs.2A and 3A). The electrolyte leakage and malondialdehyde (MDA) content were higher significantly under high temperature stress (Figs.2B and 3B). The proline (Pro), ascorbic acid (AsA), glutathione (GSH), soluble protein and soluble sugar contents were lower significantly by high temperature stress than those of the control (Figs.4,5 and 6). Both the rate of grain filling and grain dry matter accumulation become lower significantly under high temperature stress (Figs.7 and 8). Therefore, it was suggested that high temperature accelerated the senescence of rice leaf and decreased the photosynthesis rate during grain filling period, and then which was the main reason in physiology which resulted the decrease of grain filling rate, seed setting rate, grain weight and yield.