| In order to provide irrigation references for rice growth, taking rice variety Yinjing 2 as test material, the
effects of different irrigation threshold treatments (20%, 40%, 60%, 40%) on growth characteristics and yield of rice were
studied. The results as following: the trend of growth, physiological characteristics, photosynthesis and yield of rice was
basically consistent under different irrigation threshold, growth indicators (taproot length, height, stem diameter, leaf area index, specific leaf weight, aboveground and underground biomass), physiological indicators (protective enzymes like SOD,POD, CAT and protective enzymes like PPO, PAL and photosynthetic characteristics [photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (Gs), intercellular CO2 concentration (Ci), light compensation point(LCP), light saturation point of (LSP), apparent assets (AQY), carboxylation efficiency (CE), limiting value of stomata (Ls), water use efficiency (WUE)] first increased and then decreased with the increase of irrigation threshold, while the free proline and malondialdehyde (MDA) decreased. When the irrigation threshold was 60% of the relative water content of medium, each index of seedling growth was greater than that of seedlings under other irrigation thresholds, followed by the 80% treatment and the lowest was the 20% treatment, so it was suggested that 60%-80% of the relative water content of medium could be the optimum irrigation threshold in rice raising. We also concluded that irrigation threshold did not change the daily variation of photosynthetic characteristics of rice. The daily variation of Pn was in bimodal curve, and stomatal limitation resulted in different levels of photosynthetic “lunch break” phenomenon, while the daily variation of Ci, Gs and EVAP was in “W”word which were opposite to Pn. |
