外源GA3对紫斑牡丹幼苗叶片解剖结构与光合特性及内源激素含量的影响

以1年生紫斑牡丹幼苗为试验材料,采用不同浓度(0、100、300、500 mg/L)赤霉素(GA_3)喷施叶片处理,通过透射电镜、扫描电镜、光学显微镜观察幼苗叶片解剖结构,光合仪测定幼苗光合参数并以酶联免疫吸附法测叶片内源激素含量,探究外源GA_3对紫斑牡丹幼苗叶片解剖结构、光合特性和内源激素水平的影响。结果表明:(1)低浓度GA_3处理的紫斑牡丹叶肉细胞增大,栅栏组织外层细胞中叶绿体数量增加,高浓度GA_3处理则与之相反;GA_3处理叶片的栅栏组织/海绵组织比值(P/S)、组织结构紧密度(CTR)均下降,而其组织结构疏松度(SR)增加;GA_3处理的幼苗叶片的叶肉细胞内各叶绿体大小显著大于对照,随着GA_3处理浓度增加,紫斑牡丹叶肉细胞内叶绿体的体积趋于增大,类囊体垛叠凝聚逐渐松散,叶绿体上淀粉颗粒在300 mg/L GA_3处理中较明显;叶片气孔长度、宽度、气孔器大小、气孔开度和气孔密度随着GA_3浓度升高先升高后下降,同时叶片上表皮角质层厚度随GA_3浓度的升高而增加。(2)紫斑牡丹叶片净光合速率(P_n)、气孔导度(Cond)、蒸腾速率(T_r)、水分利用率(WUE)在100和300 mg/L GA_3处理下大都显著高于对照,且300 mg/L GA_3处理显著高于其余处理,而其在500 mg/L GA_3处理下显著低于对照。(3)紫斑牡丹叶片脱落酸(ABA)和吲哚乙酸(IAA)含量均在500 mg/L GA_3下显著高于对照,而在其余浓度处理下不同程度低于对照,叶片内源玉米素核苷(ZR)和GA_3含量均在300 mg/L GA_3处理下显著高于其余处理和对照,而其余处理相比对照均无显著变化;叶片的ZR/ABA、ZR/IAA、ZR/GA_3和(IAA+GA_3+ZR)/ABA比值都在300 mg/L GA_3处理下显著高于其他处理,叶片的IAA/ABA和ABA/GA_3比值均在500 mg/L GA_3处理下显著高于其他处理。研究发现,适宜浓度外源GA_3处理,能显著提高紫斑牡丹幼苗叶片光合速率、水分利用效率及蒸腾速率,调节植物体内源激素的含量及平衡,从而使叶片能合成较多有机物,促进幼苗生长。

Anatomical Structure, Photosynthetic Characteristics and Endogenous Hormones in Leaves of Paeonia rockii Seedlings under Exogenous GA3 Treatment

The one year old seedlings of Paeonia rockii were used as test materials, and different concentrations (0, 100, 300, 500 mg/L) of gibberellin (GA₃) were sprayed on the leaves, and the anatomical structure of the seedling leaves was observed by transmission electron microscope, scanning electron microscope and optical microscope. Photosynthetic instrument was used to measure the photosynthetic parameters of the seedlings, and the enzyme linked immunosorbent method was used to measure the endogenous hormone content in the leaves, to explore the effect of exogenous GA₃ on the anatomical structure, photosynthetic characteristics and endogenous hormone levels of the seedlings of P. rockii. The results showed that: (1) the mesophyll cells of P. rockii treated with low concentration GA₃ increased, and the number of chloroplasts in the outer cells of the fence tissue increased, while the high concentration GA₃ treatment was the opposite; the ratio of fence tissue/sponge tissue (P/S), tissue structure compactness (CTR) decreased, and its tissue structure porosity (SR) value increased; the size of each chloroplast in the mesophyll cells of the seedling leaves treated with GA₃ was significantly larger than that of the control. As the concentration of GA₃ treatment increased, The volume of chloroplasts in the mesophyll cells tends to increase, the stacks of thylakoids are gradually loosened, and the starch granules on the chloroplasts are more obvious in the 300 mg/L GA₃ treatment; the length, width, stomatal apparatus size, stomata opening of leaves and stomata density increased at first and then decreased with the increase of GA₃ concentration, and the thickness of the upper epidermal stratum corneum of the leaves increased with the increase of GA₃ concentration. (2) The net photosynthetic rate (P_n), stomatal conductance (Cond), transpiration rate (T_r), and water use efficiency (WUE) in leaves of P. rockii were significantly higher than those of the control under 100 and 300 mg/L GA₃ treatments. The 300 mg/L GA₃ treatment was significantly higher than the other treatments, while it was significantly lower than the control under the 500 mg/L GA₃ treatment. (3) The contents of abscisic acid (ABA) and indole acetic acid (IAA) in the leaves of P. rockii was significantly higher than that of the control at 500 mg/L GA₃, but was lower than the control to varying degrees under other treatments. The endogenous zeatin riboside (ZR) and GA₃ contents in the leaves were significantly higher than the other treatments and the control under the 300 mg/L GA₃ treatment, while the other treatments had no significant changes compared with the control; The leaves ZR/ABA, ZR/IAA, ZR/GA₃ and (IAA +GA₃+ZR)/ABA ratios were significantly higher than other treatments under 300 mg/L GA₃ treatment, and the IAA/ABA and ABA/GA₃ ratios of the leaves were significantly higher than other treatments under 500 mg/L GA₃ treatment. The study found that treatment with an appropriate concentration of exogenous GA₃ can significantly increase the leaf photosynthetic rate, water use efficiency and transpiration rate of seedlings of peony, adjust the contents and balance of endogenous hormones in the plant, so that the leaves can synthesize more organic matter and promote the growth of seedlings.