Brown R H, Bouton J H, Evans P T, Malter H E, Rigsby L L
Department of Agronomy, University of Georgia, Athens, Georgia 30602.
Plant Physiol. 1985 Mar;77(3):653-8. doi: 10.1104/pp.77.3.653.
The Laxa group of the Panicum genus contains species which have CO(2) exchange and anatomical characteristics intermediate to C(3) and C(4) photosynthetic types (C(3)/C(4)), and also species characterized as C(3). Hybrids were made between two of the C(3)/C(4) species and two C(3) species. Carbon dioxide exchange and morphological, leaf anatomical, and cytogenetic characteristics of F(1) hybrids between Panicum milioides Nees. ex Trin (C(3)/C(4)) and P. laxum Mez. (C(3)), P. spathellosum Doell (C(3)/C(4)) and P. boliviense Hack. (C(3)), and P. spathellosum and P. laxum were studied. There were no consistent differences in apparent photosynthesis, although two of the three hybrids had higher net CO(2) uptake than the C(3) parent. Values of inhibition of apparent photosynthesis by 21% O(2), CO(2) loss in the light, and CO(2) compensation concentration for the hybrids were between those of the parents. All three hybrids showed leaf anatomical traits, especially organelle quantities in the bundle sheath cells, between those of their respective parents. Linear regression of CO(2) compensation concentration on the percentage of mitochondria and chloroplasts in vascular bundle sheaths of the parents and hybrids gave correlation coefficients of -0.94. This suggests that the reduction in CO(2) loss in the C(3)/C(4) species, and to a lesser degree in the F(1) hybrids, was due to development of organelles and perhaps a higher proportion of leaf photorespiration in bundle sheaths. The overall morphology of the hybrids was so different from the parents that they could be described as new taxonomic forms. The chromosomes in the hybrids were mainly unpaired or paired as bivalents indicating possible homology between some parental genomes.
黍属的拉克斯组包含具有二氧化碳交换和解剖特征介于C₃和C₄光合类型之间（C₃/C₄）的物种，以及被归类为C₃的物种。在两个C₃/C₄物种和两个C₃物种之间进行了杂交。对黍属的小米状黍（Nees. ex Trin，C₃/C₄）和拉克斯黍（Mez，C₃）、匙形黍（Doell，C₃/C₄）和玻利维亚黍（Hack.，C₃）以及匙形黍和拉克斯黍之间的F₁杂种的二氧化碳交换以及形态、叶片解剖和细胞遗传学特征进行了研究。表观光合作用没有一致的差异，尽管三个杂种中有两个的净二氧化碳吸收量高于C₃亲本。杂种的表观光合作用受21%氧气抑制的值、光照下的二氧化碳损失以及二氧化碳补偿浓度介于亲本之间。所有三个杂种的叶片解剖特征，尤其是维管束鞘细胞中的细胞器数量，都介于各自亲本之间。亲本和杂种维管束鞘中线粒体和叶绿体百分比与二氧化碳补偿浓度的线性回归给出的相关系数为-0.94。这表明C₃/C₄物种中二氧化碳损失的减少，以及在较小程度上F₁杂种中二氧化碳损失的减少，是由于细胞器的发育以及可能维管束鞘中叶片光呼吸比例较高。杂种的整体形态与亲本差异很大，以至于可以将它们描述为新的分类形式。杂种中的染色体主要未配对或配对为二价体，表明一些亲本基因组之间可能存在同源性。
