Brown R H, Bassett C L, Cameron R G, Evans P T, Bouton J H, Black C C, Sternberg L O, Deniro M J
Department of Agronomy, University of Georgia, Athens, Georgia 30602.
Plant Physiol. 1986 Sep;82(1):211-7. doi: 10.1104/pp.82.1.211.
Photosynthetic characteristics were studied in several F(1) hybrids between C(4) and C(3)-C(4) species of Flaveria. Stable carbon isotope ratios, O(2) inhibition of apparent photosynthesis, and phosphoenolpyruvate carboxylase activities in the hybrids were similar to the means for the parents. Values of CO(2) compensation concentrations were nearer to those of the C(4) parent and apparent photosynthesis was below that of both parents, being only 60 and 74% of that of the lowest (C(3)-C(4)) parent in two experiments. Reductions of CO(2) compensation concentration and O(2) inhibition of apparent photosynthesis as well as increases in carbon isotope ratios and phosphoenolpyruvate carboxylase activities compared to values in C(3)-C(4) species suggest transfer of a limited degree of C(4) photosynthesis to the F(1) hybrids. However, the lower apparent photosynthesis of the hybrids suggests that transfer of C(4) characteristics to non-C(4) species is detrimental unless characteristics associated with C(4) photosynthesis are fully developed. There was a highly significant negative correlation (r = -0.90) between CO(2) compensation concentration and the logarithm of phosphoenolpyruvate carboxylase activity in the parents and hybrids, suggesting involvement of this enzyme in controlling the CO(2) compensation concentration. Although bundle-sheath cells were more developed in leaves of hybrids than in C(3)-C(4) parents, they appeared to contain lower quantities of organelles than those of the C(4) parent. Reduced quantities of organelles in bundle-sheath cells could indicate incomplete compartmentation of partial pathways of the C(4) cycle in the hybrids. This may mean that the reduction of CO(2) compensation and O(2) inhibition of apparent photosynthesis relative to the C(3)-C(4) parents is less dependent on fully developed Kranz anatomy than is increased apparent photosynthesis.
对黄顶菊属中几种C4与C3 - C4物种之间的F1杂种的光合特性进行了研究。杂种中的稳定碳同位素比率、表观光合作用的O2抑制以及磷酸烯醇式丙酮酸羧化酶活性与亲本的均值相似。CO2补偿浓度值更接近C4亲本的值，且表观光合作用低于双亲，在两个实验中仅为最低（C3 - C4）亲本的60%和74%。与C3 - C4物种相比，CO2补偿浓度的降低、表观光合作用的O2抑制以及碳同位素比率和磷酸烯醇式丙酮酸羧化酶活性的增加表明有限程度的C4光合作用已转移至F1杂种。然而，杂种较低的表观光合作用表明，除非与C4光合作用相关的特性得到充分发展，否则将C4特性转移至非C4物种是有害的。亲本和杂种中CO2补偿浓度与磷酸烯醇式丙酮酸羧化酶活性的对数之间存在极显著的负相关（r = -0.90），表明该酶参与控制CO2补偿浓度。尽管杂种叶片中的维管束鞘细胞比C3 - C4亲本中的更发达，但它们所含的细胞器数量似乎比C4亲本中的少。维管束鞘细胞中细胞器数量的减少可能表明杂种中C4循环部分途径的区室化不完全。这可能意味着，相对于C3 - C4亲本，CO2补偿的降低和表观光合作用的O2抑制对完全发育的花环结构的依赖性小于表观光合作用的增加。
