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[目的]探讨不同土壤水分条件下黄顶菊苗期光合特性的日变化规律,探究黄顶菊适应干旱胁迫的光合生理基础,为进一步预防其入侵提供理论依据。[方法]将黄顶菊种植在塑料桶中,并放于全透光的遮雨棚内,设3种土壤水分处理,即土壤相对含水量分别为田间最大持水量的80%(CK)、60%(T1)、30%(T2),对苗期黄顶菊的光合参数及相关生态因子的日变化进行测定,并比较不同处理间的差异。[结果]在CK条件下,黄顶菊的Pn日变化曲线基本呈“双峰”型,但在T1和T2处理条件下Pn呈“单峰”曲线;CK在上午11:30左右达到第1个峰值,为31.83μmol/(m2.s),13:30午休,下午15:30再次达到峰值,为23.34μmol/(m2.s)。而T1、T2在13:30达到峰值;3个处理黄顶菊叶片的Tr日变化均呈“单峰”曲线;CK与T2处理间无显著差异,而T1处理的日平均水分利用效率显著低于CK和T2处理。[结论]干旱胁迫降低了黄顶菊叶片的Pn、Tr、Sc等生理指标;净光合速率下降的原因既有气孔因素又有非气孔限制因素;干旱胁迫推迟了净光合效率峰值出现的时间;适度干旱能够有效提高黄顶菊的水分利用效率引起其抗旱性响应。
[Objective] The study aimed to investigate the diurnal variation of photosynthetic characteristics of Broussonetia papyrifera seedling under different soil moisture conditions, and to explore the photosynthetic basis of flaveria bidentis that adapts to drought stress and provide a theoretical basis for further preventing its invasion. [Method] The flaveria bidentis was planted in a plastic bucket and placed in a fully permeable shelter. Three kinds of soil moisture treatments were set up, that is, the soil relative water content was 80% of the maximum water holding capacity in the field and 60% (T1) and 30% (T2). The diurnal changes of photosynthetic parameters and relative ecological factors of Flaveria bidentis at seedling stage were determined, and the differences among different treatments were compared. [Result] The daily change curve of Pn of flaveria bidentis at “CK” was basically “bimodal”, but Pn showed “unimodal” curve under the conditions of T1 and T2. CK reached at about 11:30 am The first peak was 31.83μmol / (m2.s), the peak was again at 13:30, and the peak was again at 15:30, at 23.34μmol / (m2.s). While the T1 and T2 peaked at 13:30. The Tr-diurnal changes of all the three treatments showed “single peak” curve. There was no significant difference between CK and T2, but the average daily water use efficiency of T1 was significantly lower CK and T2 treatment. [Conclusion] The drought stress reduced the Pn, Tr, Sc and other physiological indexes of flaveria bidentis. The reasons of the decrease of net photosynthetic rate were both stomatal factors and non-stomatal limitation factors. The drought stress delayed the peak time of net photosynthetic efficiency; moderate drought Can effectively improve the water use efficiency of flaveria bidentis caused its drought response.