栽培型木薯Ku50的高光效生理特性分析

Physiological Mechanism Analysis of High Light Efficiency in Cassava Cultivar Ku 50

为探究栽培型木薯Ku50的高光效生理特性,选用野生型木薯W14,近缘野生型A4047以及栽培型木薯Ku50为材料,通过对其功能叶片光合色素含量,净光合速率(包括光合日变化及光强-光响应曲线)及不同光强条件下的叶绿素荧光参数[包括光系统Ⅱ的实际光能转换效率Y(Ⅱ)及非光化学淬灭系数NPQ]进行测定分析,研究不同品种木薯的光合生理特性。结果表明:栽培型木薯Ku50各项光合色素含量显著高于野生型木薯W14,与近缘野生型A4047无明显差异,推测Ku50及A4047具备更高的光合碳固定能力;光合日变化测定结果显示,净光合速率Ku50略大于A4047,均远大于W14,且Ku50及A4047不存在午间光抑制现象,而W14存在较明显午间光抑制现象,推测Ku50及A4047对强光的光能转化效率较高,耐强光性更强。进一步测定光强-光响应曲线结果显示,截至最大光强2500μmol/(m^(2)·s),3种木薯品种均未达到光饱和点,且随着诱导光强的升高,其净光合速率同样呈现Ku50>A4047>W14的趋势,其中Ku50可达到约40μmol/(m^(2)·s),A4047可达到约34μmol/(m^(2)·s),而W14仅可达到约15μmol/(m^(2)·s),表明Ku50的耐强光性更强,光能转化效率更高。此外,通过测定叶绿素荧光参数深入分析不同品种木薯对光能的吸收及分配利用,结果表明,在强光作用条件下,Ku50光系统Ⅱ的实际光能转化效率[-Y(Ⅱ)]显著高于W14,略高于A4047,但无明显差异(P>0.05);而Ku50的非光化学淬灭系数(-NPQ)则显著低于W14及A4047,表明Ku50耗散为热量的光能较低,反向证明Ku50其光能转化效率较高,与光合色素含量及净光合速率测定结果相统一。因此,研究结果表明,栽培型木薯Ku50高光效特性由强光诱导产生,且对强光的耐受性更强,利用率更高。

To study the physiological characteristics of high light efficiency in cassava cultivar Ku50,W14,a wild type,wild relatives of A4047 and cultivated species of Ku50 were used as the materials to investigate the character of photo-synthetic physiology during different varieties of cassava by measuring the photosynthetic pigment content on function-al leaves,net photosynthetic rate(including the photosynthetic rate curve under different light intensity and photosyn-thetic daily variation)and chlorophyll fluorescence parameters(including mainly the actual photosynthetic efficiency of PSⅡ-Y()Ⅱ,and non-photochemical quenching-NPQ).The result showed that the content of various photosynthetic pigments in Ku50 was significantly higher than that in W14,but no significant difference with that in A4047,suggesting that Ku50 and A4047 may have higher photosynthetic carbon fixation capacity.The net photosynthetic rate of Ku50 was slightly higher than that of A4047 and much higher than that of W14 on the photosynthetic daily variation and Ku50 and A4047 had no obvious midday photoinhibition phenomenon while W14 had,suggesting that Ku50 and A4047 may have higher light conversion efficiency and stronger resistance to high light.The photosynthetic rate curve under different light intensity showed that three varieties of cassava all did not arrive the light saturation point up to the maximum light intensity of 2500μmol/(m^(2)·s),and the net photosynthetic rate also showed Ku50>A4047>W14.Among them,Ku50 was about 40μmol/(m^(2)·s),A4047 was about 34μmol/(m^(2)·s),but W14 was only about 15μmol/(m^(2)·s).This result was con-sistent with photosynthetic daily variation and also suggested that Ku50 had stronger resistance to high light and higher light energy conversion efficiency.In addition,the chlorophyll fluorescence parameters were measured to analyze the absorption,distribution and utilization of light energy in different varieties cassava.The result showed that under high light the Y(II)of Ku50 was significantly higher than that of W14,but slightly higher than that of A4047 which had no significant difference(P>0.05).And the NPQ of Ku50 was significantly lower than those of W14 and A4047,indicating that the light energy dissipated into heat on Ku50 was lower than those of W14 and A4047,which in turn proved that the light energy conversion efficiency of Ku50 was higher than those of W14 and A4047,and which was consistent with the results of photosynthetic pigments content and net photosynthetic rate.In conclusion,this research proved that high light efficiency in cassava cultivar Ku50 was induced by high light,and had higher tolerance and utilization rate to high light than wild type of W14 and wild relatives of A4047.