增施铁对镉胁迫下柳树生长及光合生理性能的改善

【目的】了解Cd胁迫及增施Fe对不同柳树生长及光合生理的影响,探讨增施Fe对降低柳树Cd毒害和提高Cd耐性以及对柳树Cd修复的Fe调控作用。【方法】以旱柳‘Levante’和蒿柳无性系79026及790260为材料,利用1/2 Hoagland营养液(含25μmol/L EDTA-Na_2Fe)培养法,以不同Cd浓度(0、10、50、100μmol/L)(不增施Fe)和上述Cd浓度下增施Fe(25μmol/L)两组处理,培养42 d后测定不同柳树生长量(苗高和地径)、干物质量(根、茎、叶)、光合作用指标(叶绿素a、b含量、叶绿素a/b、净光合速率、气孔导度和胞间CO_2浓度)和Cd、Fe含量(根、茎、叶)。【结果】(1)随着Cd浓度增大,3个无性系/品种生长量、干物质量、叶绿素a、b含量、净光合速率、气孔导度和Fe含量(茎、叶)减少,叶绿素a/b、胞间CO_2浓度、Cd含量(根、茎、叶)增大,但根Fe含量在低中浓度Cd(10、50μmol/L)时逐渐增大,在高浓度Cd(100μmol/L)时减少。在相同Cd浓度胁迫下,3个无性系/品种Cd和Fe含量大小为根﹥叶﹥茎,旱柳根Cd含量大于蒿柳,但叶Cd含量小于蒿柳。(2)与低浓度Cd时增施Fe相比,在中高浓度Cd时增施Fe后,3个无性系/品种叶绿素a、b含量、旱柳‘Levante’和蒿柳79026生长量和干物质量(旱柳‘Levante’茎除外)、旱柳‘Levante’叶绿素a/b和叶片净光合速率均显著减小,而3个无性系/品种Cd含量增大,Fe含量减少。在高浓度Cd时增施Fe后旱柳‘Levante’和蒿柳790260叶Cd含量均小于中浓度Cd时增施Fe的,且旱柳Cd含量(根、茎、叶)和Fe含量(叶)均小于蒿柳。(3)增施Fe提高了Cd胁迫下柳树生长和干物质量、叶绿素a、b含量、气孔导度及胞间CO_2浓度,特别是在高浓度Cd时增施Fe后降低了3个无性系/品种根和叶Cd含量,增加了茎Cd含量,旱柳Cd含量(根、茎和叶)均小于蒿柳。【结论】Cd胁迫抑制了柳树生长和干物质积累以及叶绿素合成、光合作用,在中、高浓度Cd胁迫时,对旱柳生长和干物质量积累的抑制作用大于蒿柳;柳树根的Cd和Fe积累能力大于茎和叶,蒿柳Cd积累能力大于旱柳。增施Fe提高了Cd胁迫下柳树生长量和干物质量以及叶绿素含量,不同程度地增加了Cd含量和Fe含量,一定程度上缓解了Cd胁迫对柳树光合作用的影响,且对旱柳的影响作用大于蒿柳,这证实了Cd胁迫下增施Fe改善Cd胁迫下柳树对生长和生理的适应性。

Improvement on growth and photosynthetic physiological performance of three willow clones or cultivar under Cd treatments and supplying Fe

Objective] This paper investigated the effect of Cd concentrations with/without extra Fe on growth and pho?tosynthetic physiology of different willow clones/cultivar is to explore the role of extra Fe on reducing Cd stress and im?proving Cd tolerance of willow and to shed more light on the regulation of extra Fe under Cd stress as its results for im?portant practical significance. Method] In greenhouse, cuttings of three willow clones/cultivar, Salix matsudana 'Le?vante', S. viminalis cl. 79026 and S. viminalis cl. 790260, were used for hydroponic culture in half of Hoagland nutrient solution (25 μmol/L EDTA-Na2Fe) with Cd concentrations (0, 10, 50, 100μmol/L). In another hydroponic group, extra Fe (25μmol/L EDTA-Na2Fe) were supplied in solution with different Cd concentrations mentioned above. Growth ( height and diameter) , biomass ( root, stem and leaf) , photosynthesis indicators ( chlorophyll a and b content, ration of chlorophyll a to b, net photosynthesis, stomatal conductance and intercellular CO2 concentration) , Cd and Fe content of root, stem, leaf were measured for plants of each clone/cultivar after 42 d culture.Result] ①With the increasing of Cd concentrations in solution, growth, biomass, chlorophyll a and b content, net photosynthetic rate, stomatal conduct?ance and Fe content of stem and leaf decreased, however, ratio of chlorophyll a to b, intercellular CO2 concentration, Cd content of root, stem, leaf increased. Meanwhile, Fe content of root in three clones/cultivar decreased under low and middle Cd concentration( 10, 50 μmol/L) and decreased under high Cd concentration ( 100μmol/L) . Under the same Cd concentration, Cd and Fe content of three clones/cultivar were root> leaf> stem. Cd content of root in S. matsudana was more than that of S. viminalis, while Cd content of leaf in S. viminalis were more than that of S. matsudana. ② In comparison with that under the low Cd concentration with extra Fe, chlorophyll a and b content of three clones/cultivar, growth and biomass of S. matsudana'Levante' and S. viminalis cl. 79026 except that stem biomass of S. matsudana'Levante' , ratio of chlorophyll a to b, net photosynthetic rate of S. matsudana'Levante' were significantly decreased, while Cd and Fe content of three clones/cultivar were increased and decreased under the middle and high Cd concentra?tion with extra Fe. Under the high Cd concentrations with extra Fe, Cd content of leaf in S. matsudana'Levante' and S. viminalis cl. 790260 were less than that under low and middle Cd concentration with extra Fe. And Cd content of root, stem, leaf and Fe content of leaf in S. matsudana were less than these of S. viminalis. ③Compared with that in the cul?ture without extra Fe, extra Fe in the culture improved growth, biomass, chlorophyll a and b content, stomatal conduct?ance and intercellular CO2 concentration of willow under Cd stress, especially decreased Cd content of root and leaf and increased Cd content of stem under the high Cd concentrations with extra Fe. In addition, Cd content of root, stem and leaf in S. matsudana' were less than these in S. viminalis. Conclusion]Cd stress inhibited growth, dry biomass accumu?lation, chlorophyll synthesis and photosynthesis of willow. At middle and high Cd concentrations, inhibition on growth and dry biomass accumulation of S. matsudana was greater than that of S. viminalis. Cd and Fe accumulation capacity of root was greater than that of stem and leaf in willow, while Cd accumulation capacity of S. viminalis was greater than that of S. matsudana. Extra Fe with Cd stress increased growth, biomass, chlorophyll content, Cd and Fe content of willow. As the result, extra Fe alleviated Cd stress on chlorophyll synthesis, photosynthesis, etc. of willow while effect on S. matsudana was greater than that on S. viminalis. The results showed that extra Fe supplying could improve growth and physiological adaptation of willows under Cd stress.