紫叶紫薇品种'Ebony Embers'叶片呈现紫红色,是优良的观叶植物.为了对比紫叶和绿叶紫薇品种的叶色呈现机理和光合特性,以'Ebony Embers'和绿叶品种'Arapaho'为试验材料,测定叶片色素含量及分布、可溶性糖含量和光合生理指标.结果表明:1)'Ebony Embers'叶片中叶绿素、类胡萝卜素及花青苷含量显著高于'Arapaho',且花青苷含量的变化与叶片红色程度变化一致,为紫叶呈色的关键色素,主要分布在叶片栅栏组织和海绵组织靠近表皮的部分;2)'Ebony Embers'叶片可溶性糖显著高于'Arapaho',并且在紫叶中可溶性糖含量与花青苷含量呈显著正相关;3)'Ebony Embers'叶片净光合速率、气孔导度、蒸腾速率日变化均为单峰曲线,而'Arapaho'均为双峰曲线,'Ebony Embers'的净光合速率、气孔导度、蒸腾速率始终低于'Arapaho',表明'Ebony Embers'的光合能力低于'Arapaho',但其净光合速率的下降与叶绿素含量差异无关.'Arapaho'光饱和点显著高于'Ebony Embers',说明'Ebony Embers'耐强光的能力较弱;4)2个品种的Fv/Fm值之间没有显著差异,'Ebony Embers'的叶绿素荧光参数ΦPSI和ETR均显著低于'Arapaho',而NPQ和qN则显著高于'Arapaho',表明绿叶紫薇PSⅡ电子传递活性较高,而紫叶紫薇的热耗散效率高于绿叶紫薇,拥有更高的光保护能力.研究结果为培育紫薇优良彩叶品种及在园林中的应用提供了科学依据.
Lagerstroemia indica'Ebony Embers' with purple leaves was an excellent foliage plant. To compare and analyze the coloration mechanism and photosynthetic characteristics of purple-leafed cultivars of Lagerstroemia indica, L. indica'Ebony Embers' with purple leaves and L. indica'Arapaho' with green leaves were used to measure the content of pigments and soluble sugar, pigment distribution and the characteristics of photosynthesis. The results were as followings:1 ) the contents of chlorophyll, carotenoid and anthocyanin in leaves of 'Ebony Embers ' were significantly higher than those in'Arapaho' . The degree of purple coloration was consistent with the content change of anthocyanin in leaves, indicating that anthocyanin was the crucial pigment for purple coloration in leaves of 'Ebony Embers' . The anthocyanin was mainly distributed in palisade tissue and spongy tissue near the epidermis. 2) The content of soluble sugar in leaves of'Ebony Ember' was significantly higher than that of 'Arapaho', which showed a positive correlation with the content of anthocyanin in purple leaves. 3) The daily changes of net photosynthetic rate, stomatal conductance, transpiration rate all appeared as single-peak curves in 'Ebony Embers', while those in 'Arapaho' were all double-peak curves. Net photosynthetic rate, stomatal conductance, transpiration rate of'Ebony Embers' were lower than those of'Arapaho ' , indicating that photosynthetic capacity of 'Ebony Embers ' was lower than that of'Arapaho' . However, there was no significant correlation between the decrease in net photosynthetic rate of purple-leaf cultivar and the difference of chlorophyll content. The light compensation point of'Arapaho' was significantly higher than that of'Ebony Embers' , suggesting that'Arapaho' has higher ability to adapt to high light. 4) There were no differences between'Ebony Embers' and'Arapaho' in Fv/Fm. Both ΦPSII and ETR of'Ebony Embers' were significantly lower than those of'Arapaho', NPQ and qN were significantly higher than those of'Arapaho' , indicating that the electron transfer activity of PSⅡ in 'Arapaho ' was higher than that in 'Ebony Embers ' , while the heat dissipation efficiency of'Ebony Embers' was higher than that of 'Arapaho' , which had higher light protection capability. The results provide theoretical basis for developing new purple-leafed crape myrtle cultivars and garden application of L. indica.