树番茄幼苗叶片性状和生理参数对遮阴的响应及评价

Response and Evaluation of Leaf Traits and Physiological Parameters of Cyphoma betacea Seedlings Under Shading Environment

为探究树番茄幼苗在不同遮阴环境下叶片性状和生理响应机制,明确其幼苗光适应性及其生长的适宜光照环境,以树番茄幼苗为试验材料,研究正常光照(CK)、轻度遮阴(SL)、中度遮阴(SM)和重度遮阴(SH)4个处理对树番茄幼苗叶片性状、光合色素、非结构性碳水化合物(non-structural carbohydrates,NSC)及丙二醛(malonaldehyde,MDA)、脯氨酸(proline,Pro)、抗氧化酶等参数的影响,并通过主成分分析筛选树番茄耐阴指标,采用隶属函数对耐阴能力进行综合评价。结果表明,不同遮阴条件下树番茄幼苗各指标间均存在显著差异(P<0.05)。随着遮阴程度的加重,树番茄幼苗的叶长、叶面积及叶绿素a和类胡萝卜素含量等指标逐渐增大,叶绿素a/b及可溶性糖和淀粉含量、NSC均逐渐降低,而MDA、Pro、可溶性蛋白含量及抗氧化酶等指标呈先降低再升高的趋势,且在SM处理下最低。主成分分析表明,MDA、NSC、叶绿素总量、叶绿素a/b、叶鲜重、比叶面积、游离脯氨酸和SOD共8个指标可作为树番茄幼苗耐阴能力的鉴定指标。不同处理的综合评价排序依次为SM>SH>SL>CK。由此表明,树番茄幼苗期具有阴生特性,自然光照对树番茄幼苗存在强光胁迫;重度遮阴环境下存在明显的弱光胁迫。弱光胁迫下,树番茄幼苗主要通过增加单叶面积、叶绿素和类胡萝卜素含量,减小叶绿素a/b值,吸收更多的蓝紫光,以此来捕获更多的光能以提高光能利用率。此外,通过增加可溶性蛋白和Pro含量、提高抗氧化酶活性来缓解强光或弱光所产生的MDA毒害作用。综上,热区树番茄栽培、林下推广种植以及园林应用中可选择适当的半阴环境,遮阴强度50%左右较为适宜,为树番茄在热区栽培及林下推广种植提供了理论依据。

To explore the leaf characters and physiological response mechanism of Cyphomandra betacea under different shade environments at the seedling stage,and to determine whether the seedling stage is shady or not and the suitable light environment for its growth,the seedlings of Cyphomandra betacea were taking as experimental materials,and the different degree of shade environments were set including normal light(CK),light shading(SL),moderate shading(SM)and heavy shading(SH).The leaf characters,photosynthetic pigment,non-structural carbohydrates(NSC),malonaldehyde(MDA),proline(Pro)and antioxidant enzymes of Cyphomandra betacea seedlings were studied.The shade tolerance index of Cyphomandra betacea was screened by principal component analysis,and the shade tolerance was evaluated comprehensively by a membership function.The results showed that there were significant differences among all indexes of Cyphomandra betacea seedlings under different shading treatments.With the deepening of the shading degree,the parameters such as leaf length,leaf area and the contents of chlorophyll a and carotenoid gradually increased,while chlorophyll a/b,soluble sugar,starch content,and NSC decreased gradually,while the contents of MDA,Pro,soluble protein and the activities of antioxidant enzymes decreased at first and then increased,and the lowest value was found in SM treatment.Eight indexes were screened by principal component analysis including MDA,NSC,chlorophyll a+b,chlorophyll a/b,leaf fresh weight,specific leaf area,Pro content and SOD activity.And the average value of membership function in different treatments was followed as SM>SH>SL>CK.In conclusion,the seedling of Cyphomandra betacea had the characteristic of shade,there was strong light stress under natural light and obvious weak light stress under heavy shade.In a shaded environment,Cyphomandra betacea seedlings could absorb more blue-purple light by increasing single leaf area and contents of chlorophyll and carotenoid,and decreasing chlorophyll a/b to improve light energy utilization efficiency,and the contents of soluble protein and Pro and the activities of antioxidant enzymes increased for alleviating the toxic effect of MDA produced by strong or weak light.To sum up,Cyphomandra betacea seedlings had shady characters,suitable semi-shade environment could be more suitable for the cultivation of Cyphomandra betacea in hot area,under-forest area and garden with the shading intensity 50%,which provided theoretical basis for the cultivation and popularization of Cyphomandra betacea in hot area.