施氮期对小麦茎秆木质素合成的影响及其抗倒伏生理机制

摘要

为明确氮肥施用模式对小麦茎秆木质素合成与积累及抗倒伏能力的影响,2011-2012和2012-2013生长季,选用济麦22(抗倒伏)和山农16(不抗倒伏)品种,分析不同生育期追施氮肥处理的茎秆木质素含量和木质素合成相关酶活性,及其与抗倒伏指数和产量的关系。各处理总施氮量为240 kg hm-2,其中80 kg hm-2播前基施,其余氮肥按4种模式追施,分别是起身期和孕穗期各一半(N1)、拔节期全施(N2)、拔节期和开花期各一半(N3)和孕穗期全施(N4)。与N2和N3处理相比, N1和N4处理的茎秆木质素含量高,茎秆抗折力大,茎秆抗倒能力强。各处理对木质素合成关键酶活性有显著影响,其中N1的苯丙氨酸解氨酶(PAL)、酪氨酸解氨酶(TAL)和过氧化物酶(POD)活性较高；N2处理第2节间形成后0~7 d时PAL、TAL和POD活性显著高于其他处理,但第2节间形成后21 d时迅速下降；N3处理第2节间形成后0~21 d时PAL、TAL和POD活性低,但开花期(21 d)追氮延缓了3种酶活性的降低；N4处理显著提高了第2节间形成14 d后的酶活性。在乳熟期和蜡熟期,两品种的基部茎秆抗折力和抗倒伏指数均以N1和N4处理显著优于其他处理,并且N1和N4处理的籽粒产量也显著高于其他处理。试验结果表明,孕穗期追肥的N1和N4处理有助于提高茎秆中 PAL、TAL、POD 活性及木质素含量,提高小麦茎秆的机械强度及抗倒伏能力,降低小麦倒伏面积和倒伏程度。%For understanding the effects of nitrogen management on lignin synthesis in wheat stem and plant lodging resistance, a field experiment was conducted, using the lodging resistant cultivar Jimai 22 and the lodging sensitive cultivar Shannong 16, in 2011-2012 and 2012-2013 growing seasons. The lignin accumulation in stem, activities of enzymes related to lignin synthesis, lodging resistance index, and grain yield were evaluated under four nitrogen treatments. All treatments received 240 kg ha-1 ni-trogen during the whole growth period, in which 80 kg ha-1 was applied before sowing. The remaining nitrogen was applied at pseudo stem erection and booting stages (1:1) for N1, at jointing stage for N2, at jointing and anthesis stages (1:1) for N3, and at booting stage for N4 treatment. Compared with N2 and N3, N1 and N4 were superior in lignin content, stem mechanical strength, and lodging resistance. Nitrogen fertilization timing had significant effects on activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and peroxidase (POD). Under N1 condition, the three key enzymes were in high activity. PAL, TAL and POD activities were higher in N2 treatment than in other treatments at 0-7 d after emergence of the second internode (ESI), and dropped rapidly at 21 days after ESI. Under N3 condition, the PAL, TAL and POD activities were low at 0-21 days after ESI, and the activity decline was alleviated by the nitrogen supplement at anthesis stage (21 days after ESI). Under N4 con-dition, the activities of these enzymes were increased after 14 days of ESI. At milk and dough stages, both cultivars had higher snapping resistance of the basal stem in N1 and N4 than in N2 and N3 treatments. Besides, the lodging resistance index and grain yield were also significantly higher in N1 and N4 than in N2 and N3. These results indicated that nitrogen applied at booting stage (N1 and N4 treatments) is propitious to increase PAL, TAL, POD activities and lignin content in stem, leading to the improved stem mechanical strength and decreased lodging area and lodging degree of wheat.