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为了研究遮荫对贫瘠土壤上生长的植物存活率、相对生长率(RGR)、生物量分配模式及光合特性的影响,本文以耐荫的沙地柏和不耐荫的樟子松苗木为试材,进行全光和不同遮荫处理(35%、65%和95%),遮荫处理时间为2个生长季。结果表明,随着光照强度减弱,沙地柏的存活率和生长量没有明显变化,总生物量和RGR均呈先上升后下降的趋势,且RGR指标均为正值,茎根比显著提高;而樟子松存活率和生长量显著降低,总生物量和RGR一直呈下降趋势,且95%遮荫率下RGR为负值,茎根比显著降低。沙地柏的最大光化学效率(Fv/Fm)对遮荫更加敏感,在35%遮荫率下就显著增加,而樟子松在65%遮荫率时才开始显著增加。JIP-测定进一步表明,遮荫下沙地柏标准化荧光值(Vt)从O相到接近P相的过程中均明显低于全光照(CK),电子越过QA的能量占反应中心捕获能量的比例(ψo)、用于电子传递的量子比率(ψEo)均提高,且质体醌库(Sm)变大,质体醌库还原速率(Sm/Tfm)提高、初级醌受体被还原的次数(N)增多,单位激发态面积用于电子传递的能量(ET_o/CS_o)增加、反应中心数目(RC/CS_o)增多,单位反应中心电子传递的能量(ET_o/RC)增加,同时单位激发态面积(DIo/CS_o)和单位反应中心(DIo/RC)的热耗散的能量均降低,最终导致其性能指数(PIABS,PICS_o,PICSm)明显高于全光照。遮荫下樟子松标准化荧光值从O相到接近P相的过程中均明显高于CK,除热耗散指标外以上这些荧光参数与CK没有明显差异,甚至更低,而DIo/RC指标保持不变,最终导致其性能指数(PIABS,PICS_o,PICSm)与CK没有明显差异。以上结果暗示,沙地柏在较低的光强下能维持较高的生长量,通过维持正向碳平衡保持了较高的存活率,增加了地上生物量的比例,提高了光反应阶段电子传递的能量水平;而樟子松碳收支失衡导致了较低的存活率,地上生物量比例下降,电子传递的能量水平降低。
In order to study the effects of shading on the plant survival rate, relative growth rate (RGR), biomass allocation pattern and photosynthetic characteristics of plants grown in marginal soils, we tested the effects of shady Sabina vulgaris and shade-tolerant Pinus sylvestris var. All-light and different shading treatments (35%, 65% and 95%) were performed with shade treatment time of 2 growing seasons. The results showed that with the decrease of light intensity, the survival rate and growth of Sabina vulgaris did not change significantly, the total biomass and RGR both increased first and then decreased, and the RGR indexes were positive and the root / shoot ratio increased significantly. However, the survival and growth of Pinus sylvestris var. Mongolica decreased significantly, while the total biomass and RGR decreased continuously. The RGR value at 95% shading rate was negative and the root-shoot ratio decreased significantly. The maximum photochemical efficiency of Sabina vulgaris (Fv / Fm) was more sensitive to shading, increasing significantly at 35% shading rate, whereas Pinus sylvestris began to increase significantly at 65% shading rate. The JIP-determination further showed that the normalized fluorescence value (Vt) of Sabina volts from shady was significantly lower than that from full light (CK) from O phase to near P phase, and the ratio of the energy of electrons crossing QA to the capture energy of the reaction center ψo) and the quantum ratio (ψEo) for electron transfer increased, and the plastid quinone library (Sm) became larger and the reduction rate of mass quinone library (Sm / Tfm) (ET_o / CS_o) increased, the number of reaction centers (RC / CS_o) increased, and the electron transfer energy per unit reaction center (ET_o / RC) increased while the area of unit excited states DIo / CS_o) and unit reaction centers (DIo / RC) all decreased, eventually resulting in a significantly higher performance index (PIABS, PICS_o, PICSm) than that of full illumination. The normalized fluorescence values of Pinus sylvestris var. Mongolica were significantly higher than those of CK from the O phase to the near P phase under shading. Except for the heat dissipation index, these fluorescence parameters showed no significant difference or even lower than that of CK, while the DIo / RC index Remained unchanged, eventually leading to no significant difference between its performance index (PIABS, PICS_o, PICSm) and CK. The above results suggest that Sabina vulgaris can maintain a higher growth at lower light intensity, maintain a higher survival rate by maintaining the positive carbon balance, increase the proportion of aboveground biomass, and increase the photons The imbalance of carbon budget of Pinus sylvestris resulted in lower survival rate, the proportion of above-ground biomass decreased and the energy level of electron transfer decreased.