末次刈割时间对3种紫花苜蓿越冬前后根颈非结构碳氮含量的影响

Effect of last cutting dates on contents of non-structural carbon and nitrogen in root necks of three alfalfa varieties before and after overwintering

【目的】研究科尔沁沙地3种2年生紫花苜蓿品种越冬前后根颈非结构碳氮含量对末次刈割时间的响应。【方法】选择3种2年生紫花苜蓿(WL168HQ、WL298HQ、佳盛),在不同时间(2020年8月11日(C1)、8月26日(C2)、9月13日(C3)、9月27日(C4)、10月13日(C5))进行末次刈割,于2020年10月15日(T1)、11月10日(T2)、2021年3月10日(T3)、4月10日(T4)、5月10日(T5)挖根采样,测定3种紫花苜蓿越冬前(T1、T2)和越冬后(T3、T4、T5)根颈中的非结构碳氮含量。【结果】越冬前随时间推移,3种紫花苜蓿不同末次刈割处理根颈淀粉含量均呈现降低趋势,可溶性糖含量均呈现升高趋势;越冬前11月份和越冬后3月份,WL298HQ品种C2刈割处理根颈淀粉和可溶性糖含量显著高于其他末次刈割处理(P<0.05);越冬前11月份和越冬后4月份,佳盛品种C2刈割处理、WL168HQ品种C3处理根颈淀粉和可溶性糖含量显著高于其他末次刈割处理(P<0.05)。从秋冬到翌年返青,根颈游离氨基酸含量呈先上升后下降的趋势;在晚秋时节(T1),3种紫花苜蓿均以C5刈割处理游离氨基酸含量最高;次年3月份(T3)和5月份(T5),3种紫花苜蓿各末次刈割处理根颈游离氨基酸含量变化无规律性。晚秋时节(T1),WL168HQ和佳盛的C4刈割处理可溶性蛋白含量显著低于其他末次刈割处理(P<0.05);晚秋时节(T1)和返青萌动期(T4),WL298HQ的C4和C3刈割处理可溶性蛋白含量分别显著低于其他3个末次刈割处理(P<0.05)。在4月份返青萌动期,WL298HQ所有刈割处理根颈淀粉和可溶性糖含量均低于WL168HQ和佳盛;在越冬前的10和11月份,WL168HQ所有刈割处理根颈可溶性蛋白含量均高于WL298HQ和佳盛。【结论】越冬前的10月和11月,抗寒性强的苜蓿品种根颈可溶性蛋白含量高于抗寒性弱的品种;越冬后的4月份,抗寒性强的苜蓿品种根颈淀粉和可溶性糖含量高于抗寒性弱的品种。抗寒性越强的苜蓿品种,较晚进行末次刈割对其抗寒能力的影响越小。

【Objective】This study investigated the response of non-structural carbon and nitrogen contents in root necks of three overwintering alfalfa varieties to last cutting dates in the Horqin Sandy Land.【Method】Three 2-year-old alfalfa varieties(‘WL168HQ’,‘WL298HQ’and‘Jiasheng’)were selected and last cutting was carried out on different dates of August 11(C1),August 26(C2),September 13(C3),September 27(C4)and October 13(C5)in 2020.Root sampling was performed on October 15,2020(T1),November 10,2020(T2)and March 10(T3),April 10(T4)and May 10(T5)in 2021.The non-structural carbon and nitrogen contents in root necks of three alfalfa varieties before(T1 and T2)and after(T3,T4 and T5)overwintering were determined.【Result】Starch contents in root necks of alfalfa varieties decreased while soluble sugar contents increased along with time before overwintering.In November and March,contents of starch and soluble sugar in root necks of‘WL298HQ’in C2 were significantly higher than those of other treatments(P<0.05).In November and April,contents of starch and soluble sugar in root necks of‘Jiasheng’in C2 and‘WL168HQ’in C3 were significantly higher than those of other treatments(P<0.05).Contents of free amino acids in root necks increased first and then decreased from autumn to spring.In late autumn(T1),contents of free amino acids were the highest in C5.In March(T3)and May(T5),contents of free amino acids in root necks of three alfalfa varieties had no regular changes on different cutting dates.In late autumn(T1),soluble protein content in root necks of‘WL168HQ’and‘Jiasheng’in C4 was significantly lower than in those of other treatments(P<0.05)and soluble protein content of‘WL298HQ’C4 in late autumn(T1)and C3 in budding period(T4)was significantly lower than those of other treatments(P<0.05),respectively.In April the germination period of alfalfa regreening,contents of starch and soluble sugar in root necks of‘WL298HQ’were lower than those of‘WL168HQ’and‘Jiasheng’.In October and November before overwintering,soluble protein contents in root necks of‘WL168HQ’of all treatments were higher than those of‘WL298HQ’and‘Jiasheng’.【Conclusion】In October and November before overwintering,contents of soluble protein in root necks of alfalfa varieties with strong cold resistance were higher than those with weak cold resistance.In April after overwintering,contents of starch and soluble sugar in root necks of alfalfa varieties with strong cold resistance were higher than those with weak cold resistance.Alfalfa with stronger cold resistance were less affected by later last cutting.