摘要
为探讨低温弱光对西瓜光合生理特性的影响,以西瓜品种早佳(8424)为材料,研究不同温度(10、15、25 ℃)和不同光照强度(100、200 μmol·m-2·s-1)对西瓜幼苗的形态、光合指标以及抗氧化酶活性的影响.结果表明,不同低温、弱光或低温弱光复合胁迫均显著抑制西瓜幼苗生长.与对照相比,低温弱光复合胁迫(10 ℃,100 μmol·m-2·s-1)处理7 d,幼苗株高、茎粗、叶面积、地上鲜质量、株干质量、根鲜质量、根干质量分别降低28.7％、29.7％、39.1％、43.6％、60.0％、68.8％和47.7％.与对照相比,PSII最大光化学效率(Fv/Fm)和光化学猝灭系数(qP)在低温弱光处理下均呈现下降趋势.叶绿素a和总叶绿素(Chl a+b)含量降低,叶绿素a/b升高,叶绿素b含量在所有处理下变化幅度不明显.净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)在低温弱光处理下总体上显著降低,气孔导度(Gs)和蒸腾速率(Tr)在弱光胁迫下略有升高,但仍显著低于对照.与对照相比,胞间CO2浓度(Ci)和丙二醛(MDA)含量在弱光胁迫下均显著升高.综合分析,低温弱光影响西瓜生长,在低温条件下,弱光胁迫对西瓜幼苗根系生长影响最大;而在弱光条件下,温度越低对西瓜幼苗地上部生长和光合速率影响最大.
Abstract
In order to study the effects of low temperature and weak light on the photosynthetic physiological characteris-tics of watermelon,the watermelon variety Zaojia(8424)was used as the material,and three different temperature(10,15,25 ℃)and two different weak light stresses(100,200 pmol·m-2·s-1)were used to investigate their effects on the morphology,photosynthetic indicators,and antioxidant enzyme activity of watermelon seedlings.The results showed that different low temperatures,weak light,or low temperature and weak light combined stresses significantly inhibited the growth of watermel-on seedlings.Compared with the control,the plant height,stem diameter,leaf area,fresh mass,dry mass,root fresh mass,and dry mass of seedlings after 7 days of low temperature and weak light combined treatment(10 ℃,100 pmol·m-2·s-1)decreased by 28.7％,29.7％,39.1％,43.6％,60.0％,68.8％,and 47.7％,respectively.The maximum photochemical effi-ciency(Fv/Fm)and photochemical quenching coefficient(qP)of PSII both showed a decreasing trend under low tempera-ture and weak light combined treatment.The content of chlorophyll a and total chlorophyll(Chl a+b)decreased,while chlorophyll a/b increased.There was no significant difference in the changes of chlorophyll b content under all treatments.The net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)significantly decreased overall under low temperature and weak light treatment,while slightly increased under weak light stress,but still significantly lower than the control.The intercellular CO2 concentration(Ci)and malondialdehyde(MDA)content both significantly increased.In total,low temperature and weak light affect the growth of watermelon.Under low temperature conditions,weak light stress has the greatest impact on the root growth of watermelon seedlings;while under weak light conditions,the lower the temperature,the greater the impact on the aboveground growth and photosynthetic rate of watermelon seed-lings.
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