苗期遮光及光照转换对不同玉米杂交种光合效率的影响

Effects of Seedling Shading and Light Intensity Transfer on Photosynthetic Efficiency of Different Maize (Zea mays L.) Hybrids

研究了苗期遮光及光照转换对两个玉米杂交种叶片光合速率、荧光特性的影响。结果表明,遮光条件下叶片叶绿素含量,尤其是叶绿素a的含量下降,光合速率(Pn)降低,但遮光后叶绿素含量和叶绿素a/b值的下降幅度均表现为杂交种掖单2 2小于丹玉13。与此相同,遮光使丹玉13Pn 的下降显著大于掖单2 2。由遮光转入自然光下后Pn 迅速下降,4～5d之后逐渐回升,但仍无法恢复到自然光下的水平。自然光下生长的玉米转至遮光条件下时ΦPSⅡ、Fv/Fm、qp迅速上升,而NPQ呈下降趋势;而遮光的玉米转至自然光下时,各荧光参数变化趋势与之相反。这些效应在2个玉米杂交种之间有显著差异。

The intensity of light can affect morphological and physiological characters of corn leaves. Seedling stage is the key period to the differentiation and development of leaves. The lack of light in this phase will surely influence morphological construction, physiological characters and photosynthetic capability. The two-year pot-culture experiments were conducted during 2001 and 2002 to investigate the effects of seedling shading and light transfer on chlorophyll content and photosynthetic characteristics. Two light intensities were performed: CK, in which the plants were growh under natural light in seedling stage and transferred to shading condition at the sixth leave expanded stage, abbreviated to L→S, and SS, in which on the contrary above, i.e. , seedling shading and to natural light at the sixth leave expanded stage, S→L. The light intensity in the shading was half of that in natural light, and two maize hybrids, Yedan 22 and Danyu 13, were used. The results indicated that the chlorophyll content, especially chlorophyll a, decreased and net photosynthetic rate ( Pn) also declined in shading condition (Fig.1 and Fig.2) . However, the decline of chlorophyll content and chl a/chl b after shading in Yedan 22 was is slighter as compared with Danyu 13. Pn had the same trend of change with chlorophyll content, but the Pn of Danyu 13 was decreased by shading more obviously than that of Yedan 22. When the maize seedlings were in the treatment from S to L, Pn decreased immediately and continued for about 3-4 days, then began to ascend gradually and turned stable after about 6-7 days, but could not restore to the initial value (Fig.3) . From Fig.4 to Fig.7, it was shown thatΦPSⅡ , Fv/Fm and qP increased quickly while NPQ presented declining trend in the treatment from L to S; However, these fluorescence parameters changed oppositely in the treatment from S to L. These effects also varied with the hybrids.