Abstract:

Vegetables play an important role in our people's diet structure and maintain the normal physiological functions of the human body. Taking lettuce (Lactuca sativa L.) and Brassica chinensis L. as the research subjects, three treatments with different acid rain intensities (pH 5.0, 3.5, 2.5) were designed using the pot experiments with tap water (pH 7.0, CK) as the control. We studied the effects of different acid rain intensities on yield, chlorophyll fluorescence characteristics, chlorophyll mass fractions and nutritional quality of these two leafy vegetables. The results showed that pH 5.0 acid rain had no significant effect on the yield of lettuce and Brassica chinensis L. at harvest time, and acid rain at pH 3.5 and pH 2.5 caused yield of lettuce to decrease by 31.3% and 41.6%, while the yield of Brassica chinensis L. decreased by 12.2% and 27.6%. Chlorophyll fluorescence parameters of these two species under different acid rain treatments were as follows: pH 5.0>CK>pH 3.5>pH 2.5, and NPQ decreased by 21.4%—25.3% and 15.6%—19.1%, indicating that the maximum light energy conversion efficiency of the two plants increased under weak acid rain stress, while it decreased under strong acid rain stress. In the harvest period, the mass fractions of photosynthetic pigment of lettuce and Brassica chinensis L. were as follows: pH 5.0>CK, pH 3.5>pH 2.5 and CK>pH 5.0>pH 3.5>pH 2.5, respectively, and acid rain (pH 2.5) significantly reduced total chlorophyll content of these two vegetables by 30.5% and 10.7%. The mass fraction of proanthocyanidins in these two vegetables decreased significantly when treated with acid rain, while the mass fractions of soluble protein, soluble sugar, free proline and vitamin C all increased first and then decreased as the pH of the acid rain decreased. These four indexes reached the maximum value under acid rain treatment with pH 5.0, while these four indicators of Brassica chinensis L. decreased significantly by 11.8%, 22.7%, 11.9% and 16.6%, and those of lettuce decreased by 3.68%, 11.0%, 17.5% and 16.1%, respectively. The soluble protein mass fractions did not show significant difference compared with the control group. In addition, this study showed that the effect of acid rain on vegetables is related to vegetable species and acid rain acidity, and acid rain below pH 4.0 significantly reduced the yield and quality of vegetables. These findings can provide relevant references for vegetable planting and risk prevention and control.

Key words: acid rains, lettuce, Brassica chinensis L., yield, physiological characteristics, nutritional quality

摘要：

蔬菜在饮食结构中至关重要，维持着人体正常的生理功能。酸雨的频发会影响蔬菜正常生长，降低产量和品质。以生菜（Lactuca sativa L.）和上海青（Brassica chinensis L.）为研究对象，采用盆栽方法，以自来水（pH 7.0，CK）为对照，设计3个不同酸雨强度（pH 5.0，3.5，2.5）处理，研究不同酸雨强度对这两种叶菜产量、叶片叶绿素的荧光特性及其质量分数以及营养品质的影响。结果表明：pH 5.0酸雨对生菜和上海青的产量无显著影响，pH 3.5和pH 2.5酸雨分别引起生菜产量下降31.3%和41.6%，上海青产量下降12.2%和27.6%。在不同酸雨处理下，供试蔬菜的叶绿素荧光参数总体变化趋势为：pH 5.0>CK>pH 3.5>pH 2.5，且非光化学淬灭系数分别下降21.4%—25.3%和15.6%—19.1%，说明它们的最大光能转换效率在受到弱酸性酸雨作用时会升高，强酸性酸雨胁迫时降低。在收获期，两种叶菜的光合色素质量分数变化规律为：pH 5.0>CK, pH 3.5>pH 2.5和CK>pH 5.0>pH 3.5>pH 2.5，且pH 2.5酸雨处理时总叶绿素质量分数显著下降30.5%和10.7%。此外二者的原花青素质量分数在酸雨处理时显著下降，而可溶性蛋白、可溶性糖、游离脯氨酸、维生素C质量分数随着酸雨强度升高呈现先升高后下降的趋势，pH 5.0酸雨处理时这4个指标达到最大值，在pH 2.5酸雨胁迫时抑制作用最强，上海青的这四个指标与对照相比分别显著下降11.8%、22.7%、11.9%、16.6%，生菜下降3.68%、11.0%、17.5%、16.1%，其中可溶性蛋白质质量分数与对照相比无显著差异。综上，酸雨对蔬菜的影响与蔬菜种类和酸雨酸度有关，酸雨pH<3.5时，会严重影响蔬菜的产量和品质。研究结果可为蔬菜种植与风险防控提供相关参考。

关键词: 酸雨, 生菜, 上海青, 产量, 生理特性, 营养品质