小麦穗的光合特性

THE PHOTOSYNTHETIC CHARACTERISTICS OF WHEAT EAR

用电镜观察气孔器和绿色细胞的结构,用红外线气体分析仪和氧电极测定穗的光合活性,结果如下:(1)麦穗上的光合器官有芒、颖片、内外稃和穗轴。在这些器官上,仅在绿色的部位才有气孔。通常芒长和叶绿素含量高的麦穗,光合强度较高。(2)麦芒中的叶绿体具有与叶片中的叶绿体同样的结构和光化学活性。(3)提高光强和CO_2浓度,可促进穗的光合强度、穗的CO_2补偿点(110ppm)和光补偿点(200μE·m^(-2)·s^(-1))比叶片高。(4)麦穗具有光呼吸。高氧促进穗的光下CO_2释放量。麦芒上能测定出CO_2猝发和被无CO_2诱导的光合波动。这些现象表明麦穗的光合途径为C_3途径。(5)小麦穗的光合强度在开花期最高,以后随着籽粒充实,叶绿素含量下降,穗的光合强度降低。

The stomata and green cells in wheat ears were observed by electron microscopy, and the photosynthetic activity of the ears was measured with an infra-red gas analyser. 1. The awn, glume, palea, lemma, and axis were photosynthetic organs on the wheat ears. Stomata, however, only existed at the green parts in these organs. The ears which had longer awns and higher content of chlorophyll usually showed relatively high photosynthetic rates. 2. The structure and photochemical activity of the chloroplasts in the awns were similar to thore in the leaves. 3. The photosynthetic rate of ears could be promoted by increasing light intensity and CO_2 concentration. The CO_2 compensation point (110 ppm) and the light compensation point (200μE·m^(-2)·s(-1))of ears were higher than those of leaves. 4. The wheat ears had photorespiration. The CO_2-releasing rate of the ears under light could be promoted by high O_2 concentration. The CO_2 outburst and the oscillation in photosynthesis in the awns could be measured. These results suggested that the photosynthetic pathway in the wheat ears was C_8- pathway. 5. The highest photosynthetic rate of ears emerged at flowering stage. Thereafter, the photosynthetic activity of the ears fell down as the chlorophyll content declined and the grains were filled up.