海岸单叶蔓荆沙埋胁迫下碳水化合物变化与其耐沙埋的关系

选择烟台海岸沙地抗沙埋强的单叶蔓荆(Vitex trifolia var.simplicifolia)为试材,在自然环境条件下根据单叶蔓荆匍匐茎长度进行了轻度(1/3茎长)、中度(2/3茎长)和重度半埋以及全埋处理。在沙埋20d后,测定了不同沙埋处理下匍匐茎各段上匍匐茎长度、枝条高度、不定根长度,以及可溶性糖、淀粉、纤维素含量,以探讨单叶蔓荆碳水化合物变化和转化在其耐沙埋中作用。结果显示,在轻度、中度半埋和全埋下单叶蔓荆匍匐茎长度均显著大于对照,被沙埋匍匐茎处有大量不定根生成;同时,可溶性糖和淀粉含量增高和纤维素含量下降,尤其是生长最快的匍匐茎顶部(如轻度半埋),茎中可溶性糖较低、淀粉增加最多,纤维素最低。但是被重度半埋和全埋的匍匐茎生长较少,茎中纤维素含量较多、淀粉含量较少。研究表明,沙埋是一种胁迫,它损伤叶片、扰乱碳水化合物代谢平衡。但它又是胁迫信号使植物产生适应性反应,它使未遭沙埋的匍匐茎顶端通过加速碳水化合物转化、分解纤维素、提高淀粉和可溶性糖含量,为顶端生长提供能量和营养,以加速匍匐茎快速生长摆脱沙埋。同时沙埋部位枝叶通过分解其纤维素,产生更多的可溶性糖和淀粉为匍匐茎不定根生长提供能量。因此,沙埋后匍匐茎内碳水化合物的转化是其快速生长和摆脱沙埋的能量来源而在其适应沙埋生长中起重要作用。单叶蔓荆对沙埋的适应性反应表现了其具有表型可塑性特性,该特性是其沙埋后维护匍匐茎顶部快速生长、不定根形成、碳水化合物转化以及具有较高抗沙埋能力的关键。

Relationship between carbohydrate conversion and resistance to sand burial in the stolon of Vitex trifolia var. simplicifolia grown on the Coast in Yantai, China

Vitex tifolia var. Simplicafolia grown on the sandy coast of Yantai, China, was chosen as the material for this study. In these experiments, basis on stolonlength, the four levels of sand burial treatments were set up: no-sand burial, light sand burial (1/3 lengths of the stolon), moderate sand burial (2/3 lengths of the stolon), and severe sand burial (3/3 lengths of the stolon). In each sand burial treatment, the stolon was buried at two different depths, to half the shoot height and the full plant height. After 20 days of sand-burial, various parameters were measured, including the length of the stolon and adventitious roots, shoot height, and soluble sugar, starch, and cellulose content, to determine how carbohydrate conversion in the stolon of V. tifolla contributed to plant resistance to sand burial. The results showed that compared to the control without sand-burial, the stolon was much longer following light and moderate treatments (i.e., half or full height of shoot), and had new adventitious roots, higher soluble sugar and starch content and lower cellulose content In particular, under the light half sand burial treatment, the top of the V. tifolla stolon grew fast, and had the highest starch content, lowest cellulose content, and low soluble sugar content. However, under severe half sand burial and severe full sand burial treatments, the stolons grew very slowly, had higher cellulose content and lower starch content. These results indicate that sand burial represents a type of stress to these plants, which damaged the leaves and disturbed the normal balance of carbohydrate metabolism in the stolons, but also signaled the plant to activate their adaptive response. During the adaptive response, the conversion of carbohydrates was accelerated at the top of the stolon, so that cellulose content declined, while starch and soluble sugar content increased. This response may provide more nutrients and energy for the top of the stolon to grow quickly and protrude above the sand. Alternatively, cellulose in the stolon subjected to sand burial may be degraded to provide energy and nutrients to the damaged stolon to grow and survive, in addition to enhancing the growth of adventitious roots. Our results indicate that V. trifolia overcomes burial through the quick growth of the top of stolon and new adventitious roots, with carbohydrate conversion providing the energy resource and nutrition for growth. Thus, carbohydrate conversion is correlated with the capacity of the V. trifolia stolon to resist sand burial. Moreover, the capacity of V. trifolia to adapt to sand burial shows that this species exhibits phenotypic plasticity, which is important for regulating the carbohydrate balance and sustaining the stolon under sand-burial.