不同底质对海菜花叶绿素荧光诱导动力学参数及净光合速率的影响

Effects of different substrates on parameters of chlorophyll a fluorescence induction kinetics and net photosynthesis rate of Ottelia acuminata(Gagnep.) Dandy

海菜花通常被认为是对富营养化水体较为敏感的沉水植物,但近年来研究认为其对富营养化水体也有较好的净化作用。目前,海菜花在滇池回植取得一定进展,但回植时能否直接利用富营养化湖泊底泥为底质或是需要添加养分含量较少的土壤改良底泥未有明确的结论。通过对比不同底质上海菜花的光合生理参数表明:种植40d时,在湖沙和大理洱海底泥上种植的海菜花光合能力最好,红壤上种植的海菜花净光合速率仅为洱海底泥上种植海菜花的63.6%,其最大荧光(Fm)和可变荧光(Fv)比洱海底泥上种植的海菜花分别降低52.5%和58.8%,反应中心捕获的用于电子传递的能量(Eto/RC)仅为洱海底泥上种植海菜花的59.7%,光系统Ⅱ(PSⅡ)最大光化学量子产量(Fv/Fm)、性能指数(PI_(ABS))和反应中心数量(RC/CSo)也最低,叶片的单位反应中心耗散的能量(DIo/RC)是洱海底泥上种植海菜花的2.48倍,表明在红壤上种植的海菜花叶片的光合能力较低。种植80d时,不同底质上种植的海菜花的光合生理指标发生了一定改变,其中红壤上种植的海菜花光合能力大幅提升,净光合速率和性能指数等均有提高,与洱海底泥上种植的海菜花已无明显差异;然而红壤上种植的海菜花虽然在80d时的光合性能恢复,但其叶片长度已受到影响,明显低于其他底质上的海菜花的叶片长度。与此同时湖沙上种植的海菜花的光合能力在其他底质上种植的海菜花均有所增加的情况下明显下降,其净光合速率明显低于其他底质上种植的海菜花,单位面积的活性反应中心数量显著降低。结合分析不同底质的理化性质,在种植初期红壤呈酸性可能是导致海菜花叶片光合能力低的原因,之后红壤长期处于厌氧环境使得土壤pH升高后光合能力恢复正常,但其叶片的长度在短期内未有明显增加,表明其光合产物的累积受到了影响;而湖沙上种植的海菜花后期光合能力减弱可能是由于后期水体中养分耗尽导致的。因此,在回植海菜花过程中,可直接利用富营养化湖泊中的底泥,养分含量丰富的底泥不会成为其生长的限制因素,而酸性土壤可能还会限制其生长。

Ottelia acuminata （Gagnep.） Dandy is a submerged plant that is sensitive to the eutrophication of its habitat. However, some researchers argue that 0. acuminata has a purification effect on eutrophic waters. Until the 1960s, O. acuminata was the dominant species in Dianchi Lake, but it gradually disappeared beginning in the 1970s and is now extirpated utilization of eutrophic lake sediment as the substrate for replanting O. acuminata versus the improvement of eutrophic lake sediment by adding soil with low nutrient content. According to analysis the parameters of chlorophyll a fluorescence induction kinetics, the net photosynthesis rate, the leaf number and leaf length of O. acuminata on the different substrates, the result shows that the photosynthetic capacity of O. acuminata planted in Dianchi Lake sediment and Er＇ hal Lake sediment was greater on day 40 than when planted in the other sediments. Further, the net rate of photosynthesis of O. acuminata planted in the red soil was 63.6% of that observed upon planting in the Er＇hai Lake sediment, and the maximum fluorescence and variable fluorescence decreased 52.5% and 58.8%, respectively. The electron transport flux per reaction center of O. acuminata planted in the red soil was 59.7% that of when it was in Er＇hai Lake sediment, the maximum photochemical efficiency of PS II , density of reaction centers, and the performance index on absorption basis were lower than in the other samples. However, the dissipated energy flux per reaction center was 2.48 times that of the plants in the Er＇Hai Lake sediment. These results indicate that O. acuminata planted in the red soil exhibited weaker performance and weaker photosynthetic capacity. By day 80, the photosynthetic indices of the samples had changed. The photosynthetic capacity of O. acuminata in the red soil increased substantially, and the net photosynthesis rate and absorption-based performance index also exhibited similar changes. There was no difference between plants in the red soil and those in the Er＇ hai Lake sediment. Although the photosynthetic capacity of O. acuminata in the red soil had recovered by day 80, leaf length was dramatically shorter than the plants in the other groups. At the same time, the photosynthetic capacity of O. acuminata pIanted in sand of Lake dramatically declined, while others increased, and the net photosynthesic rate was lower than in the other groups. The density of the reaction centers also declined observably. Combined with the physicochemical properties of the different substrates, the acidity of the red soil is potentially what led to the initial low photosynthetic capacity of O. acuminata. The acidic soil in an anaerobic environment would increase the soil pH in the later stage and hence facilitate the recovery of the photosynthetic capacity to a normal state. However, leaf length had not increased by day 80, which indicates that it was affected by the accumulation of photosynthetic product. The decline of the photosynthetic capacity of O. acuminata in sand of Lake is likely attributable to exhaustion of nutrients in the water. Therefore, we conclude that the direct utilization of eutrophic lake sediment as a substrate is an efficient method for the restoration of O. acuminata. Additionally, lake sediment nutrients will not limit the growth of O. acuminata, while the acidic red soil will.