三种苹果砧木应对干旱胁迫的超微及解剖结构响应特性

The response characteristics of the ultrastructure and anatomical structure of three apple rootstocks under drought stress

采用盆栽控水法模拟干旱胁迫,以垂丝海棠(Malus halliana)、新疆野苹果(M.sieversii)、山定子(M.baccata)3种苹果砧木为试验材料,测定了叶片相对含水量(RWC)、水分利用效率(WUE)、光合参数,观察了叶绿体超微结构及根、茎、叶解剖结构,并采用相关性及主成分分析对砧木抗旱能力进行了综合评价。结果表明,与对照相比,干旱胁迫下,3种苹果砧木的RWC、净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)均下降,而WUE增加;3种砧木的叶绿体超微结构及解剖结构均受到不同程度的干旱伤害,但垂丝海棠的损伤最小,较好地保持细胞结构的完整性;植株的抗旱性与G_s、T_r、栅栏组织厚度、叶片厚度、下表皮厚度、根直径、韧皮部厚度均呈显著正相关,与C_i呈显著负相关;主成分分析提取的2个主成分反映了原变量100%的信息。综合评价3种苹果砧木的抗旱能力依次为:垂丝海棠>新疆野苹果>山定子;同时,RWC、G_s、T_r、栅栏组织厚度、叶片厚度、下表皮厚度、根直径、韧皮部厚度、C_i可作为评价抗旱性的有效指标。

Malus halliana, M. sieversii and M. baccata were employed as experimental materials and pot culture was used to simulate drought stress. Leaf relative water content（RWC）, water use efficiency（WUE） and photosynthetic parameters were determined, the changes in the ultrastructure and anatomic structure of three rootstocks in root, stem and leaf were investigated, and multiple indicators were analyzed by correlation analysis and principal component analysis（PCA） to evaluate drought resistance of the three apple rootstocks. The results showed that compared with normal water condition, the RWC, net photosynthetic rate（Pn）, transpiration rate（Tr）, stomatal conductance（Gs） of the three apple rootstocks showed a decline trend, whereas WUE rising under drought stress. The chloroplast ultrastructure and anatomic structure of M. halliana, M. sieversii and M. baccata had different degrees of damage under drought stress, and the magnitude of damage in M. halliana was the least and it had a more integrated cell structure than those of M. sieversii and M. baccata. According to correlation analysis, RWC, Gs, Tr, palisade tissue thickness, leaf thickness, lower epidermis thickness, root diameter and phloem thickness were positive while it correlated negatively with Ci. Two principal components were obtained which represented 100% of the total variability by PCA. In conclusion, the order of drought resistance was M. hallianaM. sieversiiM. baccata. The RWC, Gs, Tr, palisade tissue thickness, leaf thickness, lower epidermis thickness, root diameter, phloem thickness and Ci could be used as effective indices to evaluate drought resistance.