施氮水平对核桃细根呼吸速率及相关酶活性的影响

目的 以新疆南疆盆地核桃主栽品种‘新温185’（Juglans regia ‘Xinwen185’）为试验材料，探究不同施氮水平对核桃生长发育过程中细根呼吸速率及相关酶活性的影响，旨在进一步加深氮素对根系呼吸调控机理的认识。 方法 通过设置田间施肥试验，采用离体根测定法，分析核桃在不同施氮水平下细根基础呼吸速率（Q）和糖酵解途径（EMP）、三羧酸循环途径（TCA）、磷酸戊糖途径（PPP）呼吸速率的动态变化及磷酸果糖激酶（PFK）、苹果酸脱氢酶（MDH）和葡萄糖-6-磷酸脱氢酶（G-6-PDH）活性的动态变化以及细根呼吸速率与酶活性之间的相关性。 结果 随着花后时间的变化，核桃细根Q和TCA、PPP呼吸速率总体呈下降趋势，EMP呼吸速率呈先升后降趋势；细根TCA、EMP、PPP呼吸速率分别占Q呼吸速率的40.23%、33.02%、20.47%；N2水平的细根Q和TCA、PPP、EMP呼吸速率以及MDH、G-6-PDH和PFK活性高于其它施氮水平。 结论 TCA途径呼吸速率在基础呼吸速率中占比高于EMP和PPP途径呼吸速率，适量施用氮肥能够提高细根MDH和PFK活性，促进核桃细根呼吸，有利于核桃的生长，施氮水平过高或过低均会抑制细根呼吸速率，对核桃的生长造成不利影响。

Effects of Nitrogen Application Levels on Respiration Rate and Related Enzyme Activity of Walnut Root

Objective To further understand the mechanism of nitrogen regulation on root respiration of Juglans regia 'Wen185', the main walnut cultivar in South Xinjiang Basin. Method J. regia 'Wen185' was used as experimental material to study the effect of different nitrogen application levels on the fine root respiration rate and related enzyme activity during the growth and development of walnut. Field fertilizer experiment setting and in vitro root determination method were conducted to analyse the fine root's respiration rate (Q) and glycolytic pathway (EMP), Citric acid cycle Pathway (TCA), pentose phosphate pathway (PPP) respiratory rate and the dynamics of phosphofructokinase (PFK), malate dehydrogenase (MDH) and glucose-6-phosphate dehydrogenase (G-6-PDH) activity, as well as the fine root respiration rate and the correlation between enzyme activity under different nitrogen levels. Result With the changes of post-flowering time, the respiration rate of Q, TCA and PPP generally decreased, while the respiration rate of EMP increased at first and then decreased. The respiratory rates of TCA, EMP and PPP accounted for 40.23%, 33.02% and 20.47% of Q respectively. When the nitrogen level (pure quantity) was N2, the respiration rate of Q and TCA, PPP and EMP, as well as the activity of MDH, G-6-PDH and PFK were significantly higher than that of the other nitrogen application levels(P < 0.05). Conclusion TCA pathway respiratory rate occupies a higher proportion in the basic respiratory rate than EMP and PPP pathway. Proper application of nitrogen application levels could improve MDH and PFK activity, and promote root respiration of walnut, and be beneficial to the growth of walnut. Extremely low and high nitrogen application would inhibit root respiration rate and even adversely affect the growth of walnut.