Abstract: 【Objective】Soil constitution and water regimes directly affect the availability of soil water, which further influence plant growth and physiological processes. Hot pepper is one of the important economic crops in China. In this paper, the specific leaf area, photosynthesis and total evaporation of hot pepper at various soil constitution patterns and water regimes were measured. The objective of this experiment was to reveal the physiological mechanism and soil physics mechanism of hot pepper in response to soil constitution patterns and water regimes, thus providing a scientific basis for soil improvement in sandy region.【Method】A pot experiment was conducted and the hot pepper (Xiangyan 5) was used in this study. This experiment was composed of 4 soil constitution patterns (lower sand, lower soil, soil sand mixture, soil) and 3 water regimes (well-watered supply: 75%-90% field capacity (FC); moderate water stress: 60%-75% FC; severe water stress: 45%-60% FC). The specific leaf area (SLA), net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and total evaporation were measured at initial stage (Jun 28), mid stage (Jul 10), late stage (Jul 28) and the end stage (Aug 10) of flowering and fruiting stage.【Result】Through the flowering and fruiting stages, SLA was significantly higher in the lower sand treatment compared with other treatments. Net photosynthetic rate was increased by 35% and 27% higher in the soil and soil sand mixture treatments compared to lower soil treatment. Transpiration rates in the soil, sand soil mixture and lower sand treatments were 53%, 34% and 31% higher than that in the lower soil treatment. However there was no significant difference in pepper growth among the three water regime treatments. Stomatal conductance in the soil, mixture and lower sand treatments were 64%, 41% and 40% higher compared with lower soil treatment. Stomatal conductance was 29% and 36% higher in the well-watered supply and moderate water stress treatments than that in the severe water stress treatment, respectively. These results suggested that the effect of soil constitution patterns on net photosynthetic rate and transpiration rate were much greater than water regimes treatments. In addition, the effect of soil constitution on photosynthesis was related to the measuring periods and water regimes. Soil constitution had effects on the photosynthetic rate at the initial, mid and late stages, on the stomatal conductance and transpiration rate only at the initial stage. Under well-watered supply and moderate water stress regimes, the net photosynthetic rate, stomatal conductance and transpiration rate were higher in the soil and mixture treatments than lower soil treatment, but there was no significant difference between soil constitution treatments under severe water stress condition. Meanwhile, the measuring periods obviously affected the growth of hot pepper. At flowering and fruiting stages, the specific leaf area was the highest at the end stage, photosynthetic and transpiration rates were the highest at the late stage; stomatal conductance was higher at initial, mid and late stages than at end stage. The total evaporation during the four stages was affected by soil constitution and water regimes. Total evaporation was the highest in the soil treatment and the lowest in the lower soil treatment.【Conclusion】The results from this study indicated that the effect of soil constitution patterns on hot pepper growth was much greater than water regimes. Additionally, the effect of soil constitution on photosynthesis was relevant to growing stages. Therefore, for the improvement of sandy soils in the semi-arid sand region, the lower sand and soil sand mixture soil constitution patterns and the soil moisture of 60%-75% field capacity were recommended.

Key words: soil constitution , water regimes , growing period , specific leaf area , photosynthesis , total evaporation