施肥对银叶树幼苗生长及光合特性的影响

Effects of fertilization on the growth and photosynthetic characteristics of Heritiera littoralis seedlings

关键词:  银叶树幼苗, 施肥, 生长, 叶绿素, 光合特性, 叶绿素荧光

Key words:  Heritiera littoralis seedling, fertilization, growth, chlorophyll, photosynthetic characteristics, chlorophyll fluorescence

摘要:

为探讨不同施肥水平对银叶树幼苗生长和光合作用的影响,该文以2年生实生幼苗为试验材料,设置对照CK(0 g·株^-1)、N1(10 g·株^-1)、N2(15 g·株^-1)、N3(20 g·株^-1)、N4(25 g·株^-1)及N5(30 g·株^-1)6个施肥水平的盆栽实验,经140 d施肥试验,研究了不同施肥水平下银叶树幼苗的生长量、生物量、叶片叶绿素含量、光合参数及叶绿素荧光参数的变化规律。结果表明:(1)银叶树幼苗生长指标(株高与地径)、生物量(叶、茎和根生物量)、叶片叶绿素含量[Chl a、Chl b、Chl(a+b)]、叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、水分利用效率(WUE)、最大光化学效率(F_v/F_m)、实际光合效率(ΦPS Ⅱ)、表观光合量子传递效率(ETR)及光化学猝灭系数(q_P)随施肥量的增加呈先升后降的变化趋势,而胞间CO₂浓度(C_i)和非光化学猝灭参数(NPQ)则呈下降趋势。(2)幼苗叶绿素含量、根生物量及总生物量达到最大值的适宜施肥量为10 g·株^-1,幼苗生长指标(株高与地径)、叶生物量及茎生物量达到最大值的适宜施肥量为20 g·株^-1,而幼苗气体交换参数(P_n、T_r及G_s)、叶绿素荧光参数(F_v/F_m、ΦPS Ⅱ、ETR及q_P)达到最大值的适宜施肥量为30 g·株^-1,银叶树幼苗生长指标、生物量、气体交换参数及叶绿素荧光参数对不同施肥水平的响应不一致。综上所述,适量施肥能够显著增加银叶树幼苗叶片叶绿素含量、气孔导度、光化学效率及电子传递速率,降低光能的热耗散,提高银叶树幼苗的光合能力,而过量施肥导致银叶树幼苗产生光抑制,光化学效率下降,不利于银叶树幼苗正常生长。

Abstract:

In order to explore the effects of fertilization on the growth and photosynthesis in Heritiera littoralis seedlings, we used 2-year-old H. littoralis seedlings as plant material, and a pot experiment was set up with fertilization treatment of 6 levels, i.e., CK(0 g per plant), N1(10 g per plant), N2(15 g per plant), N3(20 g per plant), N4(25 g per plant)and N5(30 g per plant). This experiment lasted for 140 d, and the differences in growth, biomass, leaf chlorophyll content, photosynthetic parameters and chlorophyll fluorescence parameters were compared across different fertilization levels. The results were as follows:(1)The growth(seedling height and ground diameter), biomass(leaf, stem and root), leaf chlorophyll content [Chl a, Chl b and Chl(a+b)], leaf net photosynthetic rate(P_n), transpiration rate(T_r), stomatal conductance(G_s), water use efficiency(WUE), maximum photochemical efficiency(F_v/F_m), actual photosynthetic efficiency(ΦPS Ⅱ), apparent photosynthetic quantum transfer efficiency(ETR)and photochemical quenching coefficient(q_P)all displayed a hump-shaped trend with increasing fertilization, while intercellular CO₂ concentration(C_i)and non-photochemical quenching coefficient(NPQ)displayed a decreasing trend.(2)The growth, biomass, gas exchange parameters and chlorophyll fluorescence parameters of H. littoralis seedlings had different responses to fertilization. Specifically, seedling chlorophyll content, root mass and total biomass maximized at the fertilization level of 10 g per plant, seedling growth(height and ground diameter), leaf and stem mass maximized at 20 g per plant, and gas exchange parameters(P_n, T_r and G_s), chlorophyll fluorescence parameters(F_v/F_m, ΦPS Ⅱ, ETR and q_P)maximized at 30 g per plant. In conclusion, our results suggested that an appropriate amount of fertilization can significantly enhance the leaf chlorophyll content, stomatal conductance, photochemical efficiency and electron transfer rate in H. littoralis seedlings, resulting in lower heat dissipation and thus higher photosynthetic capacity, while over-fertilization can induce photoinhibition in H. littoralis seedlings, which decreases photochemical efficiency and suppresses seedling growth.