Effects Of Cutting Roots On The Root Architecture Of Platycladus Orientalis Seedlings

Vegetation ecological function being carried out effectively by vegetation not only depend on the surface vegetation coverage ratio but also on its configuration,especially the structure of root system under the ground.Root architecture,i.e. the growth and spatial distribution of roots in the growth medium, is the most radical and important part of root system.As it determines the abilities of root to absorb nutrient and water,so it directly affects the plant's growth and development directly.It was commonly argued that cutting roots can promote the emergence of lateral roots,and accelerate roots′abilities to absorb the nutrient and water.Then, it can increase the survival rate and decrease the cost of forestation.But, this kind of ill–healthy root system aroused by hurting directly seedlings′roots through cutting roots, will take important effects on the growth and development of seedlings in the future. Platycladus orientalis seedlings are choosen and divided into 4 groups in This experiment, including three different cutting roots radio groups (1/2 cuttingroots, 1/3 cuttingroots, 1/4 cutting roots) as treaments, and integrate roots group as a control. We studied the effects of cutting roots on the growth traits and root architecture of P.orientalis seedlings . On the foundation of this study, we discussed the mechanism of effects of cutting roots on P.orientalis seedlings, and the trend of effects on the late growth and ecological function of P.orientalis seedlings were also be furtherly analysed. The main results are as follows:1. Cutting off the main root of the P.orientalis seedlings, directly inhibit the growth and elongation of the main root.With the proportion of the roots cutting increasing, this effect is progressive. Proper proportion of root cutting significantly increase the number of lateral roots in the P.orientalis seedling root .there is a decreasing trend in the number of total roots length and tips of P.orientalis seedlings while cutting roots proportion gradually increase. At the meantime the root surface area and root volume of P.orientalis seedling also have a significantly reducing trend.2. By cutting the main root of P. orientalis seedlings, the average length of root links prominently increases, what′s more, this trend will become more and more distinctly as the cutting roots ratio increases.On the other hand, the influences of different cutting roots ratio on the number of links and crossings of roots takes on variability, and with the cutting roots ratio increasing, the decreasing rate will decrease .3. The total length of the roots having different levels of root diameter can gradually increase, and this trend will increase with the cutting roots ratio increasing. at the same time,the number of tips,root surface area and root volume of the roots having different levels of root diameter will decrease correspondly.4. 1/3 cutting roots can promote the shoot height of P.orientalis seedling growth in some extent.But generally, as the root cutting ratio increasing, the increasing trend of shoot height and basal diameter of P.orientalis seedlings has significantly decreased.In particularly,1/2cutting roots takes on obviously negative effects on the growth of shoot height and basal diameter of P.orientalis seedlings.5. The biological weight of P.orientalis seedlings can be reduced distinctly thought cutting roots.Whereas great discrepancy in effects of different cutting roots ratio on the biological weight of shoots and roots of P.orientalis seedlings doesn't present .On the other hand, with the cutting roots ratio increasing, the root-shoot rate will decrease .