以烟台、石家庄、银川和吐鲁番四个地区自然干旱梯度条件下生长的酸枣植株为试验材料,对酸枣根系的次生木质部导管及不同径级根系的分布特征进行研究。结果表明:从烟台到吐鲁番,酸枣根次生木质部中导管数量逐渐增多,管径依次增大。酸枣细根(d≤2 mm)长度远远大于其它径级根系的长度。随着干旱程度的增加,垂直方向上,细根出现在较深的土层,水平方向上,酸枣根幅扩大到560 cm,在末端或者接近末端的地方出现较多的细根分支。随着干旱程度的增加,5 mm < d < 10 mm的根系长度在总根长中所占的比例逐渐增大,其可能为干旱生境中植株根系获取水分和养分的主要部位。不同生境中酸枣根系空间分布特征的变化是其长期生存于梯度干旱环境的适应特征。
英文摘要:
Plants utilize different mechanisms to cope with drought stress; namely,drought escape,drought tolerance, drought recovery,and drought avoidance. Roots are plants' primary means of nutrient and water uptake,and also play a vital role in soil preservation while anchoring plants in place. Recently,extreme climate events such as heat waves and droughts are occurring more frequently due to global warming. Water limited conditions (also referred to as droughts) are characterized by soil moisture availability insufficient to support average plant growth and production. Under such conditions,plants must alter their root morphology in order to absorb more water and nutrients. When studying the morphological structure and distribution of root systems,it is helpful to understand the stress-resistance mechanism. Thus, the present study investigated the spatial distribution and secondary structure of the roots of Ziziphus jujuba var. spinosa, which is distributed across Yantai,Shijiazhuang,Yinchuan,and Turpan,which create a natural drought gradient because of their differences in soil moisture,annual precipitation,and humidity coefficients. The results showed that the quantity of vessels in the secondary structures of roots increased and vessel diameter also increased as drought conditions worsened along the gradient from Yantai to Turpan. In addition,Ziziphus jujuba Mill. Possessed the longest of rootlets (d≤2 mm). With increased drought stress,the proportion of fine roots distributed in the deeper soil layers gradually increased. In the horizontal direction,the root could grow to 560 cm,and a large number of rootlets grew from the end of the taproot. As drought stress increased,roots 5 mm < d < 10 mm in length made up a large proportion of the total root length. This illustrates that most of water and nutrition was acquired from this section when plants were exposed to a drought ecotope. The difference in root system distribution Ziziphus jujube Mill. in different ecotypes is an adaptive trait.