灌溉水中NaCl和Mn对棉花生长及产量的拮抗效应

Antagonistic effect of Mn and NaCl in irrigation water on cotton growth and yield

盐分和某些微量元素对植物的共同影响，不仅仅是简单的叠加效应，还可能存在一定的协同或拮抗作用。为揭示盐（NaCl）和微量元素（Mn）对棉花的影响，在中国科学院武汉植物园，采用盆栽试验，设置30组不同浓度Mn（4.5μmol·L-1、9μmol·L-1、18μmol·L-1、36μmol·L-1、72μmol·L-1）和NaCl（0、5 mmol·L-1、15 mmol·L-1、25 mmol·L-1、35 mmol·L-1、45 mmol·L-1）正交灌水处理。通过Abbott方程计算拮抗因子，评判这2个因素对棉花生长和产量的共同作用。结果表明， NaCl浓度大于25 mmol·L-1时，抑制棉花根系及地上部生长，促进棉花产量；NaCl浓度在15~25 mmol·L-1时，棉花生长情况最好；Mn浓度为36μmol·L-1时对棉花生长及产量最为有利。NaCl可促进棉花叶子中 Na积累，抑制 Mn积累；灌溉水中 Mn浓度超过18μmol·L-1时，棉花叶片中Na含量减少，而Mn含量增加。利用Abbott方程的计算结果表明， NaCl与Mn对棉花生长和产量存在显著的拮抗作用。本试验中，当灌溉水中NaCl浓度为0~45 mmol·L-1、Mn浓度为4.5~72μmol·L-1时，可以缓解NaCl或Mn作为单一因素对棉花的毒害。

The stresses of salinity and some trace elements along with the mutual relations on plant growth and yield have been well investigated and well documented in the literature. The combined effects of the two factors can be additive, antagonistic or synergistic. A soilless culture experiment was conducted to better understand the combined effects of manganese （Mn） and salinity （NaCl） on cotton growth and yield in a greenhouse at Wuhan Botanical Garden, Chinese Academy of Sciences. There were 30 orthogonal tests with six NaCl-levels and five Mn-levels in three random replicates. NaCl was added to solutions to create six NaCl-levels of concentration （0, 5 mmol·L-1, 15 mmol·L-1, 25 mmol·L-1, 35 mmol·L-1, 45 mmol·L-1） to form six electrical conductivities （EC） （2.36 dS·m-1, 2.90 dS·m-1, 3.95 dS·m-1, 5.04 dS·m-1, 6.11 dS·m-1, 7.17 dS·m-1, respectively）. The Mn factor was at five levels where MnCl2 was added to solutions to create five Mn-levels of concentration （4.5 μmol·L-1, 9μmol·L-1, 18 μmol·L-1, 36 μmol·L-1, 72 μmol·L-1）. Cotton growth, yield, dry weight and element content were measured. The results showed that salinity inhibited cotton growth but promoted cotton yield when NaCl concentration increased from 15 mmol·L-1 to 45 mmol·L-1. Cotton vegetative growth was at the best when NaCl concentration of irrigation water was 15-25 mmol·L-1. Dry weight of cotton roots and shoots decreased with increasing salinity as NaCl concentration of irrigation water increased from 25 mmol·L-1 to 45 mmol·L-1. The maximum growth and yield occurred when Mn concentration was 36μmol·L-1. Mn and salinity had a significant impact on Na and Mn accumulation in cotton leaf. Salinity promoted Na accumulation but inhibited Mn accumulation in cotton leaves. The contents of Na decreased and Mn increased in cotton leaves when Mn concentration levels in irrigation water increased from 18μmol·L-1to 72μmol·L-1. In order to independently compare the effects of salinity and Mn on cotton, growth and yield of cotton were analyzed in a two-way ANOVA analysis using the MATLAB7.6.0.324 （R2008a） software. The results showed that there were no significant influences of the interactions between salinity and Mn on cotton growth and yield. Thus the effects of the main treatments on cotton growth and yield could be presented and discussed independently. The Abbott equation was used to analyze the combined effects of Mn and salinity on cotton growth and yield and the results showed a negative relationship between Mn and salinity. In other words, the toxic effects on the growth and yield of cotton were less severe for combined Mn and salinity than the expected effects of the individual factors added together.