Department of Botany, Washington State University, Pullman, Washington 99164-4230.
Plant Physiol. 1987 Jun;84(2):461-6. doi: 10.1104/pp.84.2.461.
Photosynthetic gas exchange, activities of six key C(4) cycle enzymes, amounts of soluble protein, chlorophyll, and DNA, and various leaf anatomical and structural features were measured in naturally occurring tetraploid and octaploid plants of the NAD-malic enzyme type C(4) grass Panicum virgatum L. On a leaf area basis, the photosynthetic rate and concentrations of DNA, soluble protein, and chlorophyll were 40 to 50% higher, and enzyme activities 20 to 70% higher in the octaploid than in the tetraploid. Photosynthetic cells in the octaploid were only 17 to 19% larger in volume, yet contained 33 to 38% more chloroplasts than cells in the tetraploid. On a per cell basis the contents of DNA, soluble protein, and chlorophyll, activities of carboxylating photosynthetic enzymes, and carbon assimilation rate were all doubled in octaploid compared with tetraploid cells. Since cellular volume did not double with genome doubling, cellular constituents were more concentrated in the cells of the octaploid. The influences of polyploidy were balanced between mesophyll and bundle sheath cells since the changes in physical and biochemical parameters with ploidy level were similar in both cell types. We conclude that photosynthetic activity in these two polyploid genotypes of P. virgatum is determined by enzyme activities and concentrations of biochemical constituents, and that selection for smaller cell volume has led to higher photosynthetic rates per unit leaf area in the octaploid. The ratio of DNA content to cellular volume is a major factor determining the concentrations of gene products in cells. The number of chloroplasts, however, is controlled more by cellular volume than by the number of nuclear chromosomes.
对自然发生的 NAD-苹果酸酶型 C4 草潘那米草属四倍体和八倍体植物进行了光合气体交换、六种关键 C4 循环酶的活性、可溶性蛋白、叶绿素和 DNA 的含量以及各种叶片解剖和结构特征的测量。以叶面积为基础，八倍体的光合速率以及 DNA、可溶性蛋白和叶绿素的浓度比四倍体高 40%至 50%，酶活性高 20%至 70%。八倍体的光合细胞体积仅增大 17%至 19%，但比四倍体细胞多含有 33%至 38%的叶绿体。以单细胞为基础，八倍体细胞的 DNA、可溶性蛋白和叶绿素含量、羧化光合酶的活性以及碳同化速率均为四倍体细胞的两倍。由于细胞体积没有随基因组加倍而加倍，因此细胞内的成分在八倍体细胞中更加浓缩。多倍体的影响在叶肉细胞和维管束鞘细胞之间达到平衡，因为两种细胞类型的物理和生化参数随倍性水平的变化相似。我们得出结论，这些潘那米草属的两种多倍体基因型的光合作用活性取决于酶活性和生化成分的浓度，并且选择较小的细胞体积导致八倍体的单位叶面积光合速率更高。DNA 含量与细胞体积的比值是决定细胞内基因产物浓度的主要因素。然而，叶绿体的数量更多地受到细胞体积的控制，而不是受核染色体数量的控制。
