Study On The Root Growth Rule Of Pecan Seedling

The experiment was conducted in multiplication base of pecan seedling in Jiande,Zhejiang Province,which mainly studied on the root growth rule of pecan seedling.Several measures and many treatments were carried out,and the results showed that there were remarkable differences in the indexes of root and growth rule under different experimental conditions.Analyzing on such indexes as root biomass,root length,root surface area,root volume,root diameter and root height of different grafted pecan seedling,we could concluded that:there were extremely remarkable differences among the roots of different grafted pecan seedling.That was,the maximum of the average total root length can arrive at 2911.36cm,which was 1.82 times the total length of the minimum;the maximum of the root surface area was 573.07cm2,which is 1.79 times the size of the minimum;the differences of root volume were relative large,the maximum is 10.83cm3 equaled to 2.11 times the size of the minimum;correlation analysis on these indexes showed that each two indexes(very few exceptions)showed a significant correlation:root crown had no collation with the root diameter and the root length which was beyond grafted union,the aboveground fresh weight,the underground dry weight;but had significant positive collation with others.Among different root level of different grafted pecan seedling,the root length,root surface area and root volume were different remarkable.The root was the longest in the level of 0.0＜d＜=0.5mm, the root surface area was the biggest in the level of 1.0＜d＜=3.0mm,and the root volume was the biggest in the level of d＞3.0mm.Moreover,although in the same root level,there were relatively differences among root length,root surface area,root volume of various grafted pecan seedlings.Each index of pecan seedling was different dramatically under various water stressing. Comparing with control,the tree height and the minimum of the root diameter were reduced by 24.17%,16.14%respectively,and the indexes of root length,root surface area,the root volume were declining as the water stressing deepening and rising while rewatered,and their value were bigger than that treated by water-retaining,but were still less than the control.In different water stressing conditions,the biomass of aboveground and underground seedlings decreased as the reduction of soil moisture and increased with rewatered,but still less than the control;moreover,as the water stressing deepening,the proline contained in pecan leaves grow rapidly initial and appeared declining trend then,but it would retum to original level with rewatered.Affected on the seedling diameter,seedling height,the biomass of aboveground and underground seedling,root length,root surface area and root volume were affected by the type of container dramatically,and the level of dramatically association was beyond 0.0001.Stimulating the seedling diameter and seedling height with one-factor non-linear regression model,each model had higher decision coefficient and the adaptability was better.For example,Logistic model was preferred for root diameter;exponential model was suitable for root height.The indexes of root length,root surface area and root volume were different in various containers,and the index consequence from high to low was as follows:the former was chemical controlling container,air controlling container,ordinary cultivating container;the latter was air controlling container, chemical controlling,and ordinary cultivating container.Whether removing embryos or not had no dramatically association with root length,root surface area and root volume,comparing the root controlled by removing embryos in different containers with ones cultivated in the field,we found that root in container was longer than that in the field,especially the fine root.Measure of controlling main root and different fertilizer gradients affected the index of aboveground(seedling diameter,seedling height,fresh treetop strength,biomass and so on)and underground(root length,root surface area,root volume).That was,the indexes of underground were higher under controlling the main root than that without controlled,and the fertilizer gradients had little effect on root index.But the effect to the index of aboveground was different from to that underground,especially,the indexes of aboveground were higher under no controlling main root,middle-fertilizing or high fertilizing conditions,and lower under no fertilizing or low fertilizing conditions.Studying on the growth curving fitting of seedling diameter,seedling height and root volume,we found that each model were fitting for the growth curving very well,including Gompertz index model was suitable for root height,exponential model and index model were fitted for root volume.The indexes of aboveground cloning seedling,which appeared decline trend with the size of seed contract,not only had great effect on root diameter and root height,but also had effect on the indexes of underground root.Substrate effected the indexes of seedling diameter and seedling height,especially ordinary cultivating container,substrate types and removing embryos measures had some effect on root diameter,but had no association with root height;studying on the effect of substrate on root length, root surface area,root volume,the results were as follows:the indexes of underground had no association with container types,but effected by substrate types and removing embryos measures, especially using 40%turfs + 40%pearlite + 20%vermiculite as substrate and removing half of embryos,in this condition,the indexes reached the maximum.Studying on sowing with various root diameter,we found that the rate of seedling emergence was highest when the diameter was between 1.2cm and 1.6cm,and lowest when the diameter was between 0.4cm and 0.8cm.