不同除草剂对苜蓿苗期光合特性的影响

为明确除草剂对苜蓿苗期安全性和光合特性的影响,采用5种除草剂设低、中、高3个浓度对苗期苜蓿的叶绿素相对含量(SPAD)、净光合速率(Pn)、蒸腾速率(Tr)、胞间CO2浓度(Ci)、气孔导度(Gs)、气孔限制值(Ls)等指标进行了测定。结果表明:5种除草剂中,乙氧氟草醚药害严重,不适合苗期使用。苯达松、高效盖草能、拿捕净和苜草净均显著降低了苜蓿的SPAD、Pn、Gs、Tr和Ls值,并随着除草剂浓度的增加而进一步降低。Ci随除草剂浓度的增加而显著升高。除草剂胁迫下苜蓿的水分利用效率提高。苯达松在苜蓿苗期安全施用的剂量为1 500mL/hm2;高效盖草能对苜蓿幼苗安全的剂量为300~450mL/hm2;拿捕净的安全剂量为1 200~1 400mL/hm2;苜草净的安全施用量为1 300~2 300mL/hm2。

Effect of different herbicides on photosynthetic characteristics of alfalfa in seedling stage

In order to identify the effect of several herbicides on safty and photosynthetic characteristics of alfalfa in seedling stage,5 herbicides with high,medium and low concentrations were used to study their effects on chlorophyll relative content (SPAD),net photosynthetic rate (Pn),transpiration rate (T r ),intercellular CO2 concentration (C i )and stomatal conductance (G s ),etc.The results showed that Oxyfluorfen had the largest phytotoxicity among 5 herbicides and was not suitable for applying to alfalfa seedlings.Bntazone,Haloxyfop-R-Methyl,Sethoxydim,lmazet hay reduced the SPAD,P n ,G s ,T r and L s of alfalfa,and they were furtherly reduced with the increase of dosage.C i showed a significant rising trend along with the increase of dosage.The water use efficiency was increased under the stress of herbicides.The safe dosages of Bntazone,Haloxyfop-R-Methyl,Se-thoxydim and lmazet hay for alfalfa seedling were 1 500 ml/ha,3 00 to 4 50 ml/ha,1 200 to 1 400 ml/ha and 1 300 to 2 300 ml/ha respectively.The further field experiments should be conducted to find out the best dos-age.