Wang Keqin
Southwest Forestry College, Kunming 650224, China.
Ying Yong Sheng Tai Xue Bao. 2003 Sep;14(9):1533-7.
By means of the determination of net photosynthetic rate and transpiration rate of the leaves of seven-year field and two-year spotted Malus pumila (Goldspur) under different soil water contents and illumination and calculation of water use efficiency (WUE), the optimum soil water supply range of Malus pumila was determined. The results showed that because photosynthetic advantageous radiation (PAR) and soil water content (SWC) decided the value of photosynthetic rate and transpiration rate of Goldspur, thus they influenced the value of WUE. The response of WUE to illumination had relations with soil water. When SWC was 10% (50% of field capacity-FC) or so, the maximum of WUE was the highest value among all the soil water treatment and reached about 230 mumolCO2.g-1H2O. When the water supply was adequate (SWC > 15%), the maximum was only 160 mumolCO2.g-1H2O or so, the difference between each SWC level was not obvious and simulated curve fundamentally overlapped, although WUE decreased slowly after reached the maximum. The variation of WUE with SWC had relations with illumination. WUE was the highest while PAR was in the range of 500-1,000 mumol.m-2.s-1). Because the state of soil water decided the values of stomatic resistance (RS) and leaf water potential, RS and psi 1 also had influence on the changes of WUE. When RS and psi 1 were respectively 2.0 s.cm-1 and -3.0 MPa, WUE was the highest, but Pn was relatively low, which was not good to the normal growth and fruitage of trees. From the overall consideration of WUE, Pn and Tr, the scopes of RS and psi 1 were 2-6 s.cm-1 and -2.1 approximately -1.65 MPa, respectively, which not only guaranteed the normal photosynthesis of Goldspur, but also benefited the increase of WUE. The scope of the corresponding SWC was 11%-15%, which was equal to 55%-75% of FC and this scope could be used as theoretical index of field water supply for Goldspur.
通过测定7年生大田和2年生红星苹果在不同土壤水分含量和光照条件下叶片的净光合速率和蒸腾速率，并计算水分利用效率（WUE），确定了苹果的最佳土壤水分供应范围。结果表明，由于光合有效辐射（PAR）和土壤水分含量（SWC）决定了红星苹果的光合速率和蒸腾速率值，进而影响了WUE值。WUE对光照的响应与土壤水分有关。当SWC为10%（田间持水量-FC的50%）左右时，WUE的最大值是所有土壤水分处理中的最高值，达到约230 μmolCO2·g-1H2O。当水分供应充足（SWC>15%）时，最大值仅为160 μmolCO2·g-1H2O左右，各SWC水平之间差异不明显，模拟曲线基本重叠，尽管WUE达到最大值后下降缓慢。WUE随SWC的变化与光照有关。当PAR在500-1000 μmol·m-2·s-1范围内时WUE最高。由于土壤水分状况决定了气孔阻力（RS）和叶水势的值，RS和ψ1也对WUE的变化有影响。当RS和ψ1分别为2.0 s·cm-1和-3.0 MPa时，WUE最高，但净光合速率（Pn）相对较低，不利于树木的正常生长和结果。从WUE、Pn和蒸腾速率（Tr）的综合考虑，RS和ψ1的范围分别为2-6 s·cm-1和-2.1至-1.65 MPa左右，这不仅保证了红星苹果的正常光合作用，也有利于WUE的提高。相应的SWC范围为11%-15%，相当于FC的55%-75%，该范围可作为红星苹果田间水分供应的理论指标。
