稀土铈对太子参生长和光合特性的影响

【目的】探究稀土铈对太子参生长和光合特性的影响,以期提高太子参产量,并通过探讨铈对太子参的增产效应及其机制,为太子参高效栽培提供理论和应用依据。【方法】通过不同质量浓度稀土铈(CK、25、100、400和700 mg/L)处理后,对太子参生长指标和光合特性进行测定,并进行数据分析。【结果】随着铈质量浓度的增加,太子参植株苗高和地径相对生长量、块根长、块根直径、块根鲜质量及干质量、单位面积产量,以及叶片叶绿素和类胡萝卜素总量均表现先增加后下降的趋势,呈明显的浓度效应,以400 mg/L处理效果最佳,其中单位面积块根鲜、干质量产量分别比对照提高42.59%和41.83%。适当质量浓度稀土铈处理能显著提高光合日变化参数净光合速率(P_n)、气孔导度(Gs)、蒸腾速率(Tr)日均值,而使胞间二氧化碳浓度(C_i)降低,有效缓解光合"午休"现象。试验期间,PSⅡ最大光化学效率(F_v/F_m)、PSⅡ有效光化学效率(F_v'/F_m')、PSⅡ实际光化学效率(Φ_(PSⅡ))和光化学淬灭系数(C_(PQC))随着稀土铈质量浓度的增加均呈现先升后降的趋势,非光化学淬灭系数(CNPQ)则呈相反的趋势。相关分析表明稀土处理下苗高、地径与P_n呈极显著正相关,P_n与叶绿素含量、类胡萝卜素含量、Gs、Φ_(PSⅡ)和F_v'/F_m'呈显著正相关,而与C_i、C_(NPQ)成负相关。灰色关联分析表明,色素含量、Φ_(PSⅡ)和F_v'/F_m'和C_(PQC)是制约太子参光合作用的主要因素。【结论】适当质量浓度的稀土铈处理能有效促进太子参生长、提高块根产量,改善光合性能。其对太子参光合作用的调节作用与促进光能吸收、转换、提高光化学效率、缓解光抑制有关。与气孔因素相比,非气孔限制因子的改善是其缓解光合"午休"现象的主要原因。

Effects of cerium nitrate on growth and photosynthetic characteristics of Pseudostellaria heterophylla

Objective] In order to improve the yield of the traditional Chinese medicinal plant Pseudostellaria heterophylla and to establish a theoretical and practical basis for its high-yield cultivation,the present study investigated the stimulatory effects of cerium nitrate on photosynthesis and root tuber yield of the plant.Method] The effects of cerium nitrate on the growth indices and photosynthetic parameters of P.heterophylla were analyzed.Result] The relative growth yield of seedling height and ground diameter,root tuber length,diameter,fresh weight,dry weight,yield per unit area,and chlorophyll and carotenoid contents initially increased and then decreased in response to increasing cerium nitrate concentrations.In particular,the changes induced by the optimal cerium nitrate concentration (400 rag/L) were statistically significant.In response to cerium nitrate treatment,the fresh and dry root tuber yields per unit area increased significantly by 42.59％ and 41.83％,respectively,over that of the control treatment,and appropriate cerium nitrate concentrations also alleviated midday photosynthetic depression,improved the mean net photosynthetic rate (Pn),stomatal conductance(Gs),and transpiration rate(Tr) values associated with diurnal variation in photosynthetic parameters,and reduced intercellular CO2 concentration (Ci).During the experiment,the chlorophyll fluorescence parameters the maximal efficiency of PS Ⅱ photochemistry (Fv/Fm),the effective efficiency of PS Ⅱ photochemistry (Fv'/Fm'),the actual efficiency of PS Ⅱ photochemistry(ΦPSⅡ),and photochemical quenching(CPQC) initially increased and then decreased with increasing cerium nitrate concentrations,whereas non-photochemical quenching(CNpQ) exhibited a contrasting trend.Pn exhibited a significant positive correlation with seedling height,ground diameter,chlorophyll and carote-noid contents,GS,ΦPSⅡ and Fv'/Fm',but a negative correlation with Ci and CNPQ.And grey correlation analysis indicated that the photosynthetic pigments,ΦPSⅡ,Fv'/Fm'and CpQC were the primary factors impacting photosynthesis.Conclusion] The present study demonstrates that appropriate concentrations of cerium nitrate improve the growth,root tuber yield and photosynthetic characteristics of P.heterophylla,and that the regulatory effect of cerium nitrate on photosynthesis is related to the promotion of light energy absorption and conversion,improvement in photochemical efficiency,and alleviation of photoinhibition.Regarding stomatal factors,the inprovement of the non-stomatal limitation factor is the primary factor mitigating midday photosynthetic depression.