酸枣茎导管对自然梯度干旱生境响应的结构特征

近期因全球变暖高温干旱事件频发,严重影响植物的生长发育。逆境中植物的形态结构必定发生改变而得以生存。然而关于不同自然梯度干旱生境中植物导管形态特征变化及其规律方面的研究较少。以采自烟台、石家庄、银川和吐鲁番地区形成的自然梯度干旱条件下生长的酸枣植株为试验材料,离析观察酸枣茎次生木质部导管,研究比较不同干旱条件下酸枣茎中次生木质部导管的结构及适应特征。结果表明:酸枣茎中次生木质部导管有多种类型,不同生境中同种导管的比例不同。根据管尾情况可将导管分为三类:无尾型、一端有尾型和两端有尾型导管,且在结构上表现出特定的适应特征及规律。从烟台到新疆自然梯度干旱条件下,茎中环纹导管和螺纹导管的长度、宽度和管径总体呈减小的趋势,管壁逐渐增厚;网纹导管的宽度和直径逐渐增大;梯纹导管的长度总体呈增大的趋势,管径以宁夏的最大,新疆的最小;木纤维的宽度、管径和管壁的厚度逐渐增大。生长在不同自然梯度干旱生境中的酸枣,其导管结构的变化,提高了水分和无机盐的输导效率,可以快速补充酸枣在干旱环境中蒸腾散失的水分,抵御适应逆境,保证植株正常生长。

Changes in the vessel morphology of Ziziphus jujuba var. spinosa plants in response to natural drought-gradient ecotopes

With climate change, heat and drought events have become more frequent. A rise in temperature beyond a critical threshold for a period of time sufficient to cause irreversible damage to plant growth and development is defined as high-temperature stress. These events are often accompanied by drought. Water-limited conditions (also referred to as drought) occur when insufficient soil moisture is available to support the average plant growth and production. Plants must alter their morphology to adapt to the stress. However, little is known about the vessel characteristics of plants grown in different natural drought-gradient ecotopes. Ziziphus jujuba var. spinosa, which is distributed in the cities of Yantai, Shijiazhuang, Yinchuan, and Tulufan, was selected for this experiment. The characteristics of vessel elements in the secondary xylem in stems of Z. jujuba var. spinosa were studied using the isolation method. The results indicated that the stems of Z. jujuba var. spinosa contain various types of vessels with adaptive traits and regular patterns. The proportions of the vessel types differed among the natural drought-gradient ecotopes. The observed vessels could be divided into three types according to the number of tails: no tail, one tail, and two tails. From Yantai to Xinjiang, the length, width, and diameter of the annular vessels and spiral vessels decreased as the natural drought gradient increased, and the ply of the ductal wall thickened gradually; the width and diameter of reticulate vessels showed an increasing trend; the length of scalariform vessels also showed an increasing trend, and the diameter first increased and then decreased (Ningxia is the largest, and Xinjiang is the smallest city); the length, width, and diameter of the xylon also increased gradually. These changes in the stricture of the vessel elements, which improved their efficiency for conducting water and inorganic salts, can quickly supplement the water lost in transpiration in a dry environment, thus improving the plants'' resistance to the harsh environment and ensuring normal growth.