施氮对紫花苜蓿光合作用及抗蓟马的影响

Effect of nitrogen application on photosynthetic characteristics and resistance of alfalfa to thrips

摘要:

为探究施氮对紫花苜蓿光合作用及抗牛角花齿蓟马(Odontothrips loti)的影响,选取甘农3号和甘农9号紫花苜蓿品种,设4个施氮处理(N1,N2,N3,N4)和对照处理(N0),评价不同施氮水平下紫花苜蓿的受害程度,测定蓟马为害后紫花苜蓿的叶绿素含量和光合参数。结果表明:(1)施氮后紫花苜蓿受蓟马为害的程度加重;(2)施氮提高了紫花苜蓿叶片叶绿素含量,但随着蓟马为害时间的增加,叶绿素含量降低;(3)为害7 d后,施氮紫花苜蓿净光合速率、蒸腾速率、气孔导度和水分利用率均增大,胞间CO₂浓度降低;为害14d后,净光合速率、蒸腾速率、气孔导度和胞间CO₂浓度降低,水分利用率升高。因此,施氮导致紫花苜蓿对蓟马的抗性降低,且随紫花苜蓿受害程度的加重,光合作用进行的物质基础不足,导致紫花苜蓿对蓟马的耐害性降低。

Abstract:

The effect of nitrogen application on photosynthetic characteristics of alfalfa (Gannong No.3 and Gannong No.9) and their resistance to Odontothrips loti were studied through 4 nitrogen application treatments (N1,N2,N3,N4) and one control (N0).The damage degree of alfalfa caused by O.loti at different nitrogen application levels was evaluated,at the same time,the chlorophyll content and photosynthetic parameters of alfalfa were measured.The results showed that the damage index of alfalfa increased along with the increase of nitrogen application level.The chlorophyll content in leaves increased after nitrogen applicated,but it decreased along with the damage index.The net photosynthetic rate,transpiration rate,stomatal conductance and water use efficiency of alfalfa increased,and the intercellular CO₂ concentration decreased after alfalfa was infested by O.loti for 7 days.The net photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO₂ concentration decreased,and water use efficiency increased after alfalfa was infested by O.loti for 14 days.It could be concluded that nitrogen application reduced the resistance of alfalfa to thrips.With the increase of the damage degree of alfalfa,the materials for photosynthesis were insufficient and this resulted in the decrease of resistance to thrips.