NaCl和Zn对棉花生长及营养元素吸收的影响

微咸水在西北干旱区广泛分布, 越来越多地被运用于灌溉棉花(Gossypium hirsutum L.)等作物.微咸水中NaCl和微量元素含量比淡水高, 有关NaCl和微量元素各自对棉花生长的影响已有大量研究, 而他们对棉花生长的相互作用研究比较缺乏.选取对棉花生长作用敏感的NaCl和微量元素Zn, 开展不同NaCl和Zn浓度灌溉水盆栽试验.结果表明, 缺Zn环境下, 在灌溉水电导率为2.90~3.95 dS/m的范围内, 随着电导率增大, NaCl促进棉花根和地上部生长及皮棉产量增加.富Zn环境下, 灌溉水电导率大于5.04 dS/m时, 随着电导率增大皮棉产量明显下降.在灌溉水中Zn浓度为0.192 0~3.068 0 μmol/L的范围内, Zn浓度越大棉花营养生长越快; 大于0.767 6 μmol/L时, 随着Zn浓度增大皮棉产量下降.灌溉水中NaCl和Zn对棉花生长和产量的影响作用, 表现为相互拮抗作用关系.棉花叶的Ca、K、Mg、B和Fe含量以及铃的Cu和Zn含量高于其他组织, Na和Mn不易迁移, 易富集在棉花根部.Zn在盐胁迫条件下影响棉花对营养元素的吸收, 使棉花体内相关营养元素含量发生变化, 进而影响棉花生长及产量. 

Effects of NaCl and Zn on Growth and Nutrient Elements Uptake of Cotton

Brackish water distributes widely in arid area of Northwest China and the NaCl and trace element contents in brackish water are higher than those in fresh water. Cotton (Gossypium hirsutum L.) is likely to be affected by simultaneous NaCl and manganese toxicity stress when irrigated with brackish water. The crop yields including cotton (Gossypium hirsutum L.) are usually reduced by poor quality of irrigation water or the low contents of nutrient elements in soil. Many experiments indicate that some salinities in irrigation water or soil will affect the cotton growth and yield, and the predominant salt damage to cotton plant is from sodium (Na+). Meanwhile proper nutrient supply for cotton plant, especially trace elements for cotton, is important. Cotton diseases and abnormal growth are caused by lack or excess of trace elements. However, it remains beyond our full understanding as to the combined effect of salinity and trace elements on cotton growth and its uptake of nutrient elements. Thus we selected the trace element zinc which is sensitive to cotton growth, and conducted a pot experiment including 24 different treatments in irrigation with 6 NaCl levels (0 mmol/L, 5 mmol/L, 15 mmol/L, 25 mmol/L, 35 mmol/L and 45 mmol/L) and 4 Zn levels (0.192 0 μmol/L, 0.767 6 μmol/L, 3.068 0 μmol/L and 12.272 0 μmol/L) in three replicates randomly in a greenhouse at Wuhan Botanical Garden, Chinese Academy of Sciences. During the experiment, cotton growth of different treatments was measured every ten days after germination and cotton plants were harvested 197 days after sowing. The cotton bolls were harvested and air dried and weighted the wool without seeds to calculate the lint yields. Cotton samples of roots, stems, leaves and fruits were brushed to remove the sand and dusts, rinsed with deionized water; oven dried at 70 ℃ for two days and weighed dry weight. The dry matters of cotton for each treatment were triturated and sampled 0.5 g for acid digestion. Twenty-seven elements were measured in triplicate by ICP-OES (ICAP6300, Thermo Scientific, England). Nine of the 27 elements i.e. K, Ca, Mg, Na, B, Cu, Fe, Mn and Zn (cotton nutrient elements) are chosen for analysis in this paper. The results show that salinity promoted cotton root, steam growth and cotton lint yields when electrical conductivities (EC) of irrigation water fell in the range of 2.90 to 3.95 dS/m in the zinc deficiency environment. While in the zinc-rich environment, salinity inhibited cotton lint yields when EC was greater than 5.04 dS/m. Cotton plant vegetative growth become faster when Zn concentration of irrigation water in the range of 0.192 to 3.068 μmol/L, while when Zn concentration was greater than 0.767 μmol/L would cause cotton plant lint yields decline. Analysis of variance among cotton growth, root and stem dry weight parameters revealed significant influence by salinity effect but not by Zn. Cotton lint yield parameters revealed that the effect of Zn was more obvious than salinity. Interactive effect on cotton growth and yield between NaCl and Zn in the irrigation water was not observed but antagonistic effect was observed. Contents of nutrient elements Ca, K, Mg, B and Fe, in cotton leaves were higher than those in other organizations. Nutrient elements Cu and Zn in cotton bolls were higher than other organizations. Nutrient elements Na and Mn were not so movable that they are easily accumulated in roots. Zn concentration levels in irrigation water under salinity stress affected the nutrient elements uptake of cotton, caused different contents of nutrient elements in cotton, and then influenced cotton growth and yields.