施钾对紫花苜蓿苗期光合特性及抗蓟马的影响

Effect of potassium application on photosyntheticcharacteristics and alfalfa resistanceto Odontothrips loti

摘要:

为了探索施钾对苗期紫花苜蓿抗蓟马的影响及其光合机制,以甘农9号(Medicago sativa cv.Gannong No.9)和甘农3号(M.sativa cv.Gannong No.3)紫花苜蓿为材料,设置40,60,80和100 mg/kg 4个钾水平,以不施钾为对照(CK),评价了各钾水平下不同蓟马为害时间的苜蓿的受害程度,并测定了不同施钾水平下苜蓿功能叶片的光合特性和叶绿素含量。结果表明:施钾后,苜蓿受蓟马为害的程度显著减轻;苜蓿叶片叶绿素含量升高,但随着蓟马为害时间的延续,苜蓿的叶绿素含量较受害前期降低。为害7 d时,甘农3号苜蓿净光合速率(Pn)和水分利用率(WUE)升高、气孔导度(Gs)显著升高,除K1水平外,胞间CO2浓度(Ci)在其他施钾水平下均显著升高,除K4水平外,蒸腾速率(Tr)在其他施钾水平下均降低;甘农9号苜蓿的净光合速率、气孔导度、胞间CO2浓度均显著升高,水分利用率升高,蒸腾速率降低。为害14 d时,两个苜蓿品种的净光合速率、气孔导度均显著升高,蒸腾速率降低;甘农3号的水分利用率升高不显著,甘农9号的水分利用率显著升高;除K3水平外,甘农3号的胞间CO2浓度在其他钾水平下均升高,除K4水平外,甘农9号的胞间CO2浓度在其他钾水平下均显著降低。施钾使苜蓿叶片的叶绿素含量增加,提高了苜蓿的光合能力,进而增强了苜蓿对蓟马的抗性。

Abstract:

This study investigated the effects of potassium application on leaf photosynthetic characteristics of alfalfa and its resistance to Odontothrips loti.The study included two alfalfa varieties(Medicago sativa cv.Gannong No.9 and M.sativa Gannong No.3),four potassium(K)levels(40 mg /kg soil,60 mg /kg soil,80 mg /kg soil and 100 mg/kg soil),together with nil-K application as the control.The degree of damage in alfalfa was evaluated under different K levels at different periods,meanwhile leaf photosynthetic characteristics and chlorophyll content were measured.The results showed that the damage indexes of alfalfa infested by O.loti were reduced significantly with K application,and leaf chlorophyll content increased,but the chlorophyll content of alfalfa became lower along with the more severe damage.When Gannong No.3 was infested by O.loti for 7 days,leaf net photosynthetic rate(Pn)and water use efficiency(WUE)increased,and stomatal conductance(Gs)increased significantly,the intercellular CO2 concentration(Ci)increased significantly except unde r K1,and the transpiration rate(Tr)decreased at all potassium levels except under K4.In Gannong No.9,leaf net photosynthetic rate,stomatal conductance,and intercellular CO2 concentration increased significantly,water use efficiency increased,and transpiration rate decreased when alfalfa was infested by O.loti for 7 days.Leaf net photosynthetic rate and stomatal conductance of both alfalfa varieties increased significantly,and the transpiration rate decreased when infested by O.loti for 14 days,water-use efficiency of Gannong No.3 increased though not significant,while water-use efficiency of Gannong No.9 increased significantly.The intercellular CO2 concentration of Gannong No.3 increased at all K levels except under K3,and that of Gannong No.9 decreased significantly except under K4 when alfalfa was infested by O.loti for 14 days.Potassium application increased leaf chlorophyll content,net photosynthetic rate of alfalfa,and enhanced alfalfa resistance to thrips.