南丰蜜橘对高温热害的生理响应及耐热性评价模型构建

Physiological response to high temperature and heat tolerance evaluation of different lines in Nanfeng tangerine

【目的】探究南丰蜜橘不同品系对高温热害的生理响应,并进行耐热性评价。【方法】通过测定高温下南丰蜜橘不同品系(杨小-26和南丰-28)叶片组织结构、气孔形态和生理生化指标,评价两个品系的耐热性强弱。【结果】高温显著影响两个品系叶片组织结构和气孔形态特征;高温下两个品系的Pn下降,在24 h时是气孔因素导致的,而在48 h时是非气孔因素。高温期间杨小-26的F_(v)/F_(m)、ABS/CS_(m)、TR_(o)/CS_(m)、ET_(o)/CS_(m)和DI_(o)/CS_(m)值均高于南丰-28,而O_(2)^(-)、H_(2)O_(2)和MDA含量则小于南丰-28。在高温处理48 h时,杨小-26的SOD和CAT活性高于南丰-28。通过相关性分析和主成分分析,筛选出气孔面积、Pn、MDA、F_(v)/F_(m)和SOD作为模型构建的关键参数,构建TOPSIS的耐热性评价模型,计算出杨小-26的耐热性高于南丰-28。【结论】高温下杨小-26叶片组织更稳定、光合能量转换效率高、细胞膜损伤较轻、SOD和CAT酶的活性高是其耐热性较高的主要原因。

【Objective】In order to explore the physiological response of different lines in Nanfeng tan-gerine to high temperature and evaluate their heat resistance,the present experiment was undertaken.【Methods】With the main cultivars of Nanfeng tangerine,Yangxiao-26 and Nanfeng-28,as the experi-mental materials,the effects of 24 h and 48 h treatments at 42℃on the leaf tissue structure,stomatal morphology,photosynthetic fluorescence parameters,energy transfer,reactive oxygen species and anti-oxidant enzyme activity of plants were studied.Based on the results,an entropy weighted TOPSIS heat tolerance model was established to determine the heat resistance degrees of Yangxiao-26 and Nanfeng-28.【Results】With the extension of high temperature and time,the thickness changes of the epidermis and palisade tissue of the leaves of Yangxiao-26 and Nanfeng-28 were not significant,but the values of Yangxiao-26 were greater than those of Nanfeng-28.After 48 h high-temperature treatment,the thick-nesses of the epidermis and sponge tissue significantly decreased by 14.63%and 14.29%in Yangxiao-26,respectively,while they were 13.47%and 15.75%in Nanfeng-28,respectively.With 24 h high tem-perature treatment,there was no significant differences in the ratio of palisade tissue to spongy tissue be-tween Yangxiao-26 and Nanfeng-28,compared to the untreated group,but the difference was signifi-cant with 48 h high temperature treatment.At room temperature,the stomatal areas of Yangxiao-26 and Nanfeng-28 were 62.71μm and 54.17μm,respectively.After 48 h high-temperature treatment,the sto-matal area of both significantly decreased by 84%and 93%,respectively.High temperature had a signif-icant impact on the length and width of stomata in Yangxiao-26 and Nanfeng-28,both of which signifi-cantly decreased with the duration of high temperature treatment.The stomatal density ranges of Yangxiao-26 and Nanfeng-28 were 62.27-69.41 and 61.31-64.06,respectively,which indicated that they were not affected by high temperature treatment.The stomatal closure percentage of Yangxiao-26 and Nanfeng-28 decreased significantly with the extension of high temperature time.After 48 h high temperature treatment,the stomatal closure percentage of both decreased by 58%and 81%,respective-ly.Before high-temperature treatment,the stomatal length,width,density and closure percentage of Yangxiao-26 were all greater than those of Nanfeng-28.At room temperature,there was no significant difference in leaf Pn between Yangxiao-26 and Nanfeng-28;With the extension of high temperature time,the Pn of both showed a decreasing trend.After 48 h high temperature treatment,the Pn rates of both decreased by 57%and 82%respectively,compared to those without high temperature treatment,and at this time,the Pn of Yangxiao-26 was significantly higher than that of Nanfeng-28.The variation pattern of Gs and Pn was almost consistent,and Gs in both Yangxiao-26 and Nanfeng-28 decreased with the extension of high temperature time.The variation pattern of Ci and Ls in Yangxiao-26 and Nanfeng-28 under different treatment durations under high temperature conditions was opposite.With 24 h high temperature treatment,the Ci of Yangxiao-26 and Nanfeng-28 decreased compared to that without high temperature treatment,while the value of Ls increased compared to that without high temperature treat-ment.With 48 h high-temperature treatment,the Ci values of Yangxiao-26 and Nanfeng-28 increased compared to those without high-temperature treatment,while the Ls value decreased compared to that without high-temperature treatment.However,there was no significant difference in Ci and Ls at both 24 h and 48 h between Yangxiao-26 and Nanfeng-28.During the entire high-temperature treatment period,the maximum photochemical quantum yield(F_(v)/F_(m)),energy absorbed per unit light cross-section(ABS/CS_(m)),energy captured for reducing QA(TR_(o)/CS_(m)),energy captured for electron transfer(ET_(o)/CS_(m)),and dissipated energy(DI_(o)/CS_(m))values in the leaves of Yangxiao-26 were consistently higher than those of Nanfeng-28;With the increase of high temperature duration,the contents of superoxide anion(O2-),hy-drogen peroxide(H_(2)O_(2))and Malondialdehyde(MDA)in the leaves of Yangxiao-26 and Nanfeng-28 in-creased continuously,and the contents of O_(2)^(-),H_(2)O_(2)and MDA in the leaves of Yangxiao-26 were always lower than those of Nanfeng-28.With the increase of high-temperature treatment time,the ascorbic acid peroxidase(APX)activity in the leaves of Yangxiao-26 and Nanfeng-28 significantly increased.The su-peroxide dismutase(SOD)activity in the leaves of Yangxiao-26 increased with the extension of high temperature treatment time,while the SOD enzyme activity in the leaves of Nanfeng-28 first increased and then decreased with the extension of high temperature treatment time.With 24 h of high temperature treatment,there was no significant difference in leaf SOD enzyme activity between Yangxiao-26 and Nanfeng-28,but after 48 hours of treatment,the SOD enzyme activity in Yangxiao-26 leaves was signifi-cantly lower than that of Nanfeng-28.The order of catalase(CAT)activity in the leaves of Yangxiao-26 was 48 h>24 h>0 h,while in the leaves of Nanfeng-28,the order of CAT enzyme activity was 24 h>0 h>48 h.Moreover,with high temperature treatment for 24 h,the CAT enzyme activity of Yangxiao-26 was significantly higher than that of Nanfeng-28,while with high temperature treatment for 48 h,the CAT enzyme activity of Yangxiao-26 was significantly lower than that of Nanfeng-28.Based on the above physiological parameters,a heat tolerance evaluation model based on entropy weighted TOPSIS was constructed,and it was found that the heat tolerance of Yangxiao-26(0.6784)was higher than that of Nanfeng-28(0.4129).【Conclusion】The main reasons for higher heat resistance of Yangxiao-26 un-der high temperature conditions are its more stable leaf tissue,high photosynthetic energy conversion ef-ficiency,less damage to cell membrane and high activity of SOD and CAT enzymes.