低温条件下黄瓜嫁接株与自根株光合特性的比较

研究了长期低温条件下,设施黄瓜嫁接苗和自根苗(播种后35 d)的净光合速率(P n)、表观量子效率(AQY)、气孔导度(G s)、蒸腾速率(T r)和胞间CO2浓度(C i)与光通量密度(PFD)的关系.结果表明:不同PFD条件下,经过长期低温后黄瓜嫁接苗和自根苗叶片的光饱和点、AQY、P n、G s和T r均较适温条件下显著下降,但嫁接黄瓜下降速度及程度显著低于自根黄瓜.适温条件下,黄瓜C i随PFD增加而降低;低温条件下,嫁接黄瓜C i也随PFD增强而降低,自根黄瓜则始终保持较高水平.以上结果表明,长期低温条件下,黄瓜嫁接苗与黄瓜自根苗均发生气孔抑制现象,但嫁接苗较自根苗保持相对较高的气孔导度,维持较高的光合同化效率,产生较少的过剩激发能,光合器官的伤害程度降低,因而有较强适应低温的能力.

Comparison of Photosynthetic Characteristics of Grafted and Own-root Seedlings of Cucumber under Low Temperature Circumstances

The study probed the relations of the net photosynthetic rates(Pn),apparent quantum yields(AQY),stomatal conductance(Gs),transpiration rates(Tr) and intercellular CO_2 concentrations(Ci) with the photosynthetic flux densities(PFD) of grafted and own-root seedlings(35 days after sowing) of greenhouse-planted cucumber under long-time low-temperature circumstances.The results showed that at different photosynthetic flux densities(PFD),grafted and own-root seedlings suffering long-time low temperature significantly decreased in light compensation point,apparent quantum yield,Pn,Gs and Tr compared with those growing at normal temperature,but grafted seedlings decreased at a low rate and by a smaller range than own-root seedlings.the Ci of both grafted and own-root seedlings declined with increased photosynthetic flux density(PFD) at normal temperature;at low temperature,the Ci of grafted seedlings rose with increased photosynthetic flux densities(PFD) whereas the Ci of own-root seedlings kept at a high level no matter how much the photosynthetic flux density(PFD) increased;those above show that under long-time low temperature circumstances,both grafted and own-root seedlings suffered stamatal limitation but grafted seedlings maintained a higher level in stomatal conductance,photosynthetic and assimilation efficiencies,produced a smaller amount of surplus excitation energy,suffered lighter damage to their photosynthetic organs thereby having stronger adaptability to low temperature,compared with own-root seedlings.