夏季遮光减缓芍药叶片衰老的光合机制研究

Study on photosynthetic mechanism of summer shading slowing aging of herbaceous peony(Paeonia lactiflora) leaves

为探究夏季强光和轻度遮荫对芍药(Paeonia lactiflora)衰老生理的影响,以主栽品种‘紫凤羽’、‘红凤羽’及芍药野生种为供试材料,设大田全光照及轻度遮荫处理,分析夏季强光(SL)和轻度遮荫(SS)对芍药叶片光合特性、叶绿素荧光参数、叶绿体超微结构、膜脂过氧化等的影响。结果表明:SS处理92 d后,各供试材料叶绿体呈典型的椭圆状,内外膜结构清晰完整,基粒和类囊体膜结构垛叠紧密;野生种、‘红凤羽’和‘紫凤羽’绿色期分别延长了40、20和10 d,且根增重率分别增加了119.76%、67.74%和1.42%。在SS处理下‘红凤羽’和野生种净光合速率(P_n)和表观量子效率(AQY)降低幅度均小于‘紫凤羽’,说明‘红凤羽’和野生种的遮荫效果明显好于‘紫凤羽’。在SS处理下‘红凤羽’和野生种的电子传递速率(ETR)和实际光化学反应效率(Φ_(PSⅡ))的增加幅度均大于‘紫凤羽’,说明在SS处理下‘红凤羽’和野生种的光抑制程度受影响更小。在光保护机制方面,‘红凤羽’和野生种在轻度遮荫处理下其调节性能量耗散(NPQ)下降幅度大于‘紫凤羽’,且叶黄素循环(A+Z)/(A+Z+V)上升幅度大于‘紫凤羽’,说明SS处理下‘红凤羽’和野生种与‘紫凤羽’相比更倾向于通过叶黄素循环途径耗散过量的激发能,以保护光合器官免受伤害。在膜脂过氧化方面,各供试材料在前期SS处理下其超氧化物歧化酶(SOD)活性、超氧化物歧化酶活性/丙二醛含量(SOD/MDA)和相对电导率(RIL)变化幅度不显著,其中‘红凤羽’和野生种更稳定;但在9月1日的SS处理下,各供试材料SOD活性显著降低,且RIL显著上升,说明因外界光强降低而轻度遮荫表现为弱光逆境,使得遮荫延缓衰老进程效果具有阶段性。研究结果为选育强光耐受性强的品种和实现根高产栽培提供依据。

In order to investigate the effect of strong light（SL） and slight shading（SS） on the senescence physiology of herbaceous peony（Paeonia lactiflora） in summer, main cultivars ‘Zi Fengyu＇, ‘Hong Fengyu＇ and wild species were used as test materials. We Set up full field lighting and mild shading treatment, and analyzed the effects of summer SL and SS on photosynthetic characteristics, chlorophyll fluorescence parameters, chloroplast ultrastructure and membrane lipid peroxidation in herbaceous peony leaves. The results show that： after 92 days of SS treatment, the chloroplasts of all tested materials were typically elliptic, the structures of internal and external membranes were clear and complete, and the structures of basal granules and thylakoid membranes were tightly stacked. The green period of wild species, ‘Hong Fengyu＇ and ‘Zi Fengyu＇ were prolonged by 40, 20 and 10 days, respectively, and the root weight gain rate increased by 119.76%, 67.74% and 1.42%, respectively. Under SS treatment, the net photosynthetic rate（Pn） and apparent quantum efficiency（AQY） of ‘Hong Fengyu＇ and wild species were lower than those of ‘Zi Fengyu＇. This result indicats that the shade effects of ‘Hong Fengyu＇ and wild species were significantly better than those of ‘Zi Fengyu＇. The increases in electron transfer rate（ETR） and actual photochemical efficiency（Φ（PSⅡ）） of ‘Hong Fengyu＇ and wild species under SS treatment were greater than those of ‘Zi Fengyu＇, showing that the degrees of photoinhibition of ‘Hong Fengyu＇ and wild species are less affected by SS treatment. In terms of photoprotective mechanisms, ‘Hong Fengyu＇ and wild species decreased their non-photochemical quenching coefficient（NPQ） more than ‘Zi Fengyu＇ under the SS treatment, and xanthophyll cycle（A＋Z）/（A＋Z＋V） increased more than ‘Zi Fengyu＇, indicating that in order to protect photosynthetic organs from injury, ‘Hong Fengyu＇ and wild species are more prone to xanthophyll cycle pathway to dissipate excess excitation energy when compared to ‘Zi Fengyu＇ under SS treatment. In terms of membrane lipid peroxidation, the changes of superoxide dismutase（SOD） activity, SOD activity/malonaldehyde content（SOD/MDA） and relative electrical conductivity（RIL） of each test material under previous SS treatment were not significant, but ‘Hong Fengyu＇ and wild species were more stable among them. However, under SS treatment on September 1, the activity of SOD of each test material was significantly reduced, and RIL increased significantly, indicating that SS showed low light stress due to the decrease of external light intensity, which made the shading delaying the aging process in stages. This provides a theoretical basis for the breeding of varieties with SL tolerance and the realization of high yield root cultivation.