缺磷对不同磷效率基因型大豆光合日变化的影响

用1/2 Hoagland营养液培养磷高效大豆基因型BX10和磷低效基因型BD2，缺磷胁迫15d后测定其光合、光呼吸、暗呼吸的日变化。并进一步探讨了影响上述过程的原因。结果表明：缺磷使两基因型光合速率（Pn）显著下降，但BX10仍高于BD2（尤其在上午）；缺磷对PSⅡ光化学效率（Fv／Fm）和胞间CO2浓度（Ci）的影响无规律可循，与Pn的相关性也不显著；缺磷显著降低大豆气孔导度（Gs）．并与Pn呈极显著正相关（r=0．753。P〈0．001）。暗呼吸（Rd）与Pn日变化趋势相近（r=0．706，P〈0．01），但缺磷对其影响不大；缺磷下光呼吸（Pr）显著下降，而Pr／（Pn＋Pr）在BX10中却相对提高。光呼吸相对加强可能有助于磷高效基因型同补叶绿体光合作用所需的无机磷（Pi）。

Effect of P Deficiency on Diurnal Variation of Photosynthesis in Contrasting Soybean Genotypes

Two contrasting soybean genotypes(P-efficient BX10 vs.P-inefficient BD2) were hydroponically grown in 1/2 Hoagland solution and subjected to phosphorus(P) deficiency for 15d.Physiological responses to P deficiency were determined in terms of photosynthetic rate(Pn),photorespiration and dark respiration as well as possible factors governing these processes.The results indicated that Pn was markedly reduced in both genotypes by P deficiency.No clear pattern was observed on the response of photochemical efficiency(Fv/Fm) and intercellular CO2 concentration(Ci) to P deficiency and both did not correlated with Pn.Phosphorus deficiency markedly decreased the stomotal conductance(Gs) and it was positively correlated with Pn(r=0.753,P<0.001).The diurnal variation pattern of dark respiration(Rd) was similar to Pn(r=0.706,p<0.01) but it was little affected by P deficiency.Photorespiration rate(Pr) was reduced whereas the Pr/(Pn+Pr)in BX10 was enhanced in response to P deficiency.Such relative increase in photorespiration may play a role in replenishing Pi into photosynthetic process.