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CAS Workshop on Ecosystem Succession Theory and Practice of Ecological Restoration Mycorrhizal effects on chromium tolerance and
accumulation in soybean Mei Beijian1
Fred T. Davies2 Jeffrey
D. Puryear1 Ronald
J. Newton3 (1Dept.
of Forest Science, Texas A&M University, College Station, TX
77843; 2Dept. of Horticultural Sciences, Texas A&M
University, College Station, TX 77843; 3Dept. Biology,
East Carolina University, Greenville, NC 27858) Abstract:
The effects of mycorrhizal fungi on chromium tolerance and
accumulation in soybean (Glycine
max) var. Mitchell-450 was investigated in a greenhouse pot
culture study. In Cr(VI) treatment, VAM led to a substantial
increase of plant height, leaf area, and dry mass accumulation.
Further, It enhanced gas exchange, especially stimulating net
photosynthesis and stomatal conductance. It also enhanced essential
element uptake including N, P, K, Mg, B, Zn and Mo, and reduced
non-essential element uptake such as Al and Na. It seems that VAM
helped plants to exclude Cr leading to a 28% lower tissue
concentration in roots. This reduction of Cr concentration
alleviated Cr toxicity and enhanced plant growth. Thus, VAM treated
plants grew to a bigger size, produced a higher biomass, and
eventually had a 54% higher total uptake of Cr per plant. VAM
treatment may be promising for enhancing phytoremediation functions
of soybean in Cr(VI) contaminated soils. VAM effects were quite
different between the Cr(III) and Cr(VI) treatments. Soybean plants
demonstrated the typical characteristics of a heavy-metal
hyperaccumulator species, accumulating significant amounts of Cr in
tissues and having more Cr moving into the above-ground parts when
exposed to a high concentration of Cr(III) (12 mM). However,
mycorrhizae colonization, net photosynthesis and growth of plants
were severely inhibited in VAM as well as non-VAM plants, leading to
quick senescence and high mortality due to the toxicity of the high
concentration of Cr (III). Key words:
soybean; mycorrhizae; chromium; phytoremediation; gas exchange 共生菌对于黄豆忍耐和累积重金属铬能力的影响 摘要：通过温室的盆栽实验,我们研究了共生菌对于黄豆
(Glycin max)
var.Mitchell-450忍耐和累积重金属铬能力的影响.在六价铬的处理中,VAM
明显促进了植株高度,叶面积以及干物质的积累.
而且,
VAM促进了气体交换,特别是增进了静光合作用和气孔开启.
VAM还增进了必要元素氮,磷,钾,镁,硼,锌和钼的吸收,同时减少非必要元素如铝和钠的吸收.看来,
VAM能帮助植株排斥铬的吸收,因而根部组织铬含量比对照低28%,这样一来,减少了六价铬对植株的毒性,反过来促进了植株的生长.结果,
VAM处理的植株比对照长得更高大,产生更多的干物质,最后,单株累积的铬金属比对照多54%.因此,用VAM处理增进黄豆在修复六价鉻所造成环境污染中的作用可能有良好前境.
黄豆对VAM的反应,在六价和三价铬的处理之间很不相同.当黄豆植株生长在含高浓度的三价鉻
(12 mM) 的土中,
植株表现出典型重金属累积物种的特征,不单吸收更多的铬,而且有更多的铬从根部运输到茎叶.不过,由于高浓度三价铬的毒性,
无论有没有VAM的处理,
共生菌菌落计数,
静光合作用以及植株生长同样受到严重抑制,
而且植株迅速衰老和死亡.
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