Chongqing Key Laboratory of the Three Gorges Area Forest Ecology Protection and Restoration, Chongqing Academy of Forestry, Chongqing, 400036, China.
College of Resources and Environment, Southwest University, Chongqing, 400716, China.
Environ Sci Pollut Res Int. 2016 Jun;23(11):11171-11180. doi: 10.1007/s11356-016-6315-z. Epub 2016 Feb 27.
We studied the growth of roots of white mulberry (Morus alba) trees in response to different water and nutrient conditions in sets of three or five containers connected via small pipes and arranged so as to simulate the heterogeneous soil conditions associated with rocky desertification. The experiment was conducted to improve understanding of the adaptation of M. alba to this stressful environment. The trees were grown for a year under constant water and nutrient conditions in the soils within each container of any set of containers. Differences in root activity and endogenous hormones within root tips were measured at the end of the experiment. We compared four treatment groups: H (variable moisture among containers), F (variable nutrients among containers), HF (both moisture and nutrients varied among containers), and CK (non-varied control). Results showed the following: (1) Mulberry roots showed obvious hydrotropic and chemotropic growth patterns, but chemotropism did not occur in the condition of water shortage. (2) Measurement of growth indices (root surface area, total root length, number of root tips, root biomass) showed that growth status was best in group HF once the roots were able to access containers with sufficient water and nutrients, followed by group H. The indices were significantly poorer in groups F and CK. (3) The content of auxin, cytokinin, and gibberellins in roots under soil drought conditions were lower than under wetter soil conditions. In contrast, abscisic acid content and root activity were higher under soil drought conditions than under wetter soil conditions. The results indicated that water is the key factor restricting growth of white mulberry trees in areas of rocky desertification but that the trees adjust endogenous hormones in their roots to promote tropic growth and obtain sufficient moisture and nutrients over the long term. Moreover, under long-term drought stress conditions, mulberry trees retained high root activity which appears to be adaptive in that all of the trees survived.
我们研究了白桑（Morus alba）根系在通过小管道连接的三组或五组容器中的不同水和养分条件下的生长情况，这些容器的排列方式模拟了与石漠化相关的不均匀土壤条件。这项实验旨在增进对白桑适应这种胁迫环境的理解。在任何一组容器中的土壤中，所有容器都保持恒定的水和养分条件下，这些树木生长了一年。在实验结束时，测量了根尖内的根活性和内源性激素的差异。我们比较了四个处理组：H（容器间水分可变）、F（容器间养分可变）、HF（容器间水分和养分都可变）和 CK（非变化对照）。结果表明：（1）桑树根表现出明显的向水性和向化性生长模式，但在缺水条件下，向化性没有发生。（2）生长指标（根表面积、总根长、根尖数、根生物量）的测量表明，一旦根系能够接触到有足够水分和养分的容器，HF 组的生长状况最好，其次是 H 组。F 组和 CK 组的指标明显较差。（3）在土壤干旱条件下，根中的生长素、细胞分裂素和赤霉素含量低于较湿润土壤条件下的含量。相比之下，在土壤干旱条件下，根中的脱落酸含量和根活性高于较湿润土壤条件下的含量。结果表明，水是限制白桑在石漠化地区生长的关键因素，但树木会调整其根部的内源激素，以促进向性生长并长期获得足够的水分和养分。此外，在长期干旱胁迫条件下，桑树保持了较高的根活性，这似乎是适应性的，因为所有的树木都存活了下来。
