镉胁迫对大蒜苗生理特性的影响及施钙的缓解效应

Effect of cadmium stress on physiological characteristics of garlic seedlings and the alleviation effects of exogenous calcium

通过营养液水培方式,研究了镉(Cd2+)对大蒜苗生长、光合特性、叶片酶活性及主要矿质元素吸收的影响及增施不同浓度钙(Ca2+)对镉胁迫大蒜苗的缓解效应.结果表明:与正常生长的大蒜苗相比,施镉能明显降低大蒜苗的形态指标(株高、假茎粗、假茎长及鲜质量),减少叶片的色素含量、净光合速率(Pn)、蒸腾速率(E)及气孔导度(gs),减弱叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性并增加丙二醛(MDA)含量,减少根中矿质元素(N、P、K、Ca、Mg)含量并增加Cd含量.增施钙能显著促进镉胁迫大蒜苗的生长,随所增施钙浓度的提高,大蒜苗的形态指标均呈现先增大后减小的趋势,在其浓度为2或3 mmol·L-1时达到峰值;同时,增施钙也可有效提高镉胁迫大蒜叶片的色素含量及光合参数(Pn、E、gs),其变化趋势与形态指标类似,均在所增施钙浓度为2或3 mmol·L-1时最高;另外,增施钙能增强镉胁迫大蒜叶片的抗氧化酶(SOD、POD、CAT)活性并降低MDA含量,还可增加根中矿质元素(N、P、K、Ca、Mg)含量并减少Cd含量,且施钙浓度为2或3 mmol·L-1时效果最好.

In the experiment, the effects of exogenous cadmium （ Cd2＋ ） and calcium （ Ca2＋ ） in nu- trient solution on growth, photosynthetic characteristics, enzymes activities, main mineral elements absorption of garlic seedlings were studied. The results showed that cadmium could obviously inhibit the growth of garlic seedlings, decrease the pigment contents and photosynthetic parameters （Pn, E, gs） of leaves, reduced the enzymes （ SOD, POD, CAT） activities and increase the MDA con- tent of leaves, and also could reduce the N, P, K, Ca, Mg contents and increase the Cd content of roots. The growth was promoted after adding exogenous calcium to garlic seedlings under cadmium stress, which reflected that the morphological indexes were increased at first and then decreased with the increase of exogenous calcium concentrations, and were maximized when the exogenous calcium was 2 or 3 mmol ·L-1. At the same time, the pigment contents and photosynthetic parame- ters （Pn, E, gs） of leaves showed a similar tendency with the morphological indexes, and they were the highest when the exogenous calcium was 2 or 3 mmol· L-1. In addition, adding exogenous calcium to garlic seedlings under cadmium stress enhanced the enzymes （SOD, POD, CAT） activi- ties and decreased the MDA content of leaves, also added the N, P, K, Ca, Mg contents and re- duced the Cd content of roots, and the effect was best when the exogenous calcium concentration was 2 or 3 mmol· L-1.