两种土壤含水率下匙羹藤的光合及水分利用率的初步研究

采用便携式LI-6400光合测定系统,对生长于两种土壤含水率下的当年生匙羹藤光合特性及其水分利用率进行研究。结果表明:(1)匙羹藤叶片的光饱和点(LSP)200～400μmol.m-2.s-1,光补偿点(LCP)12.1880～12.5593μmol.m-2.s-1,表观量子利用效率(α)0.0472～0.0508mol.mol-1,为阳生植物,但具有较强的弱光利用能力。(2)叶片CO2补偿点为70.97～73.75μmol.mol-1,CO2饱和点在1115.51～1687.99μmol.mol-1,羧化效率7.35×10-3～8.64×10-3μmol.m-2.s-1,表明匙羹藤为C3型植物。(3)上午10:00左右和下午4:00左右是匙羹藤水分利用率的最高时段。(4)含水率高时饱和净光合速率(Pm)、表观光合量子利用效率(α)、光饱和点都比含水率低时高,但光补偿点却比含水率低时低,说明匙羹藤利用弱光的能力较强,能有效地利用全日照的强光,光合潜力较大,生长较好;含水率低时匙羹藤的CO2补偿点较低,说明匙羹藤能利用较低的外界CO2浓度;最大水分利用效率较高,表明含水率低时匙羹藤的节水潜力较大。

Primary study on the photosynthesis and the water use efficiency of Gymnema sylvestre under two soil water contents

The research of photosynthesis physiological characteristic and the water use efficiency of one-year-old Gymnema sylvestre growing in the soil under two water contents was conducted by using the portable LI-6400 photosynthesis determining system.The results were showed:(1)The light saturation point,the compensation point,and the apparent quantum use efficiency for the leaf of G.sylvestre were 200～400 μmol·m-2·s-1,12.188 0～12.559 3 μmol·m-2·s-1,0.047 2～0.050 8 mol·mol-1 respectively,indicating G.sylvestre to be heliophyte,but with strong ability to use weak light.(2)The CO2 compensation point is 70.97～73.75 μmol·mol-1,the CO2 saturation point is 1 115.51～1 687.99 μmol·mol-1,the carboxyl efficiency is 7.35×10-3～8.64×10-3 μmol·m-2·s-1,indicating G.sylvestre to be C3 plant.(3)The most effective time to use water is 10:00 am and 4:00 pm.(4)G.sylvestre had higher Pm,α and LSP but a lower LCP in high water content soil than in low water content soil indicated the fact that,when the water content was higher,G.sylvestre had stronger ability to use weak light and could effectively use the entire sunshine,well grown and with a strong photosynthesis power;when the water content was lower,with a small CO2 compensation point,it could use the low CO2 concentration and had a high efficiency to absorb water.