Physiological And Biochemical Effects Of Nitrogen Supply On Root Respiration Of Walnut Seedlings

As the center of metabolism of underground part of plant,root respiration not only provides energy for the growth and development of plant,but also drives the metabolism of the whole plant by consuming carbon nutrition produced by photosynthesis on the ground.Therefore,root respiration is the main way of carbon and nitrogen cycle of plant.In this paper,the seedlings of walnut(Juglans regia Linn.),the main economic tree species in Xinjiang,were taken as the research object.Based on the controlled nitrogen application experiment under the potted condition,the respiratory characteristics of roots of different diameter classes of walnut and their response to nitrogen supply level were taken as clues.With the help of technical means such as whole plant digging,instrument measurement and laboratory chemical analysis,the mathematical statistical analysis method was used to analyze The relationship between the content of non structural carbohydrate,the activity of key enzymes in nitrogen metabolism,the seasonal variation of root activity and the respiration rate of roots was studied.The main results are as follows:The root respiration rate of walnut seedlings was the highest at the level of 16N,while the root activity was the highest at the level of 8N and 4N at the early stage and the end stage of seedling growth,respectively;the root respiration rate and root activity of each diameter class increased first and then decreased with the growth season;the respiratory rate per unit surface area increased with the increase of root diameter class,and the specific root respiration rate and root activity increased with the increase of root diameter class Lower.Under different nitrogen supply levels,the root respiration rate and root activity of walnut seedlings were significantly correlated.The content of soluble sugar and starch in the roots of walnut seedlings was the highest at the level of 16N under different nitrogen supply levels,which was significantly higher than other nitrogen supply levels(P<0.05);with the growth of the season,the content of soluble sugar and starch showed the trend of "up down up down down",at the same time,the content of both increased with the increase of root diameter.The contents of soluble sugar and starch in roots were negatively correlated with specific root respiration rate(P<0.01),and positively correlated with respiration rate per unit surface area(P<0.01).Under different nitrogen supply levels,the soluble protein content and NR activity of walnut seedling root increased with the increase of nitrogen supply level,and the GS activity first increased and then decreased with the increase of nitrogen supply level;the soluble protein content in the coarse root of walnut seedling was higher than that in the fine root,and the NR and GS activities increased with the increase of root diameter level;the soluble protein content and GS activity in the root of walnut seedling at different diameter levels in different months And NR activity were significantly correlated with respiratory rate.The results showed that the regulation of nitrogen on the root respiration of walnut seedlings was mainly realized by regulating the metabolism of nitrogen and carbon in the roots.In the growth stage of walnut seedlings,appropriate application of nitrogen fertilizer can improve the respiratory rate of roots,promote the consumption of non structural carbohydrates,and provide energy for nitrogen metabolism.