镉污染对烤烟光合特性、产量及其品质的影响

Effects of Cd pollution on photosynthetic characteristics,yield and quality of tobacco leaves

采用盆栽方法,研究了Cd污染对烤烟叶片光合特性、烟叶品质及其产量的影响。结果表明,随着Cd处理浓度的增加,烟叶净光合速率(Pn)和气孔导度(Gs)逐渐降低,胞间CO2浓度(Ci)随Cd浓度的增加逐渐增大;光系统Ⅱ活性(Fv/Fo)、最大光能转换效率(Fv/Fm)、光化学猝灭系数(qP)、非光化学猝灭系数(NPQ)、电子传递的量子产率(ФPSⅡ)和有效电子传递速率(ETR)则随Cd浓度的增加而降低;烤烟烟叶中的糖/碱比和氮/碱比升高,化学成分组成趋于不协调,不利于烟叶香吃味的形成。

In order to understand the mechanism of the effect of Cd pollution on photosynthesis, quality and yield of tobacco leaves, pot experiments were carried out at the Research Station of Henan Agricultural University during 2002 - 2004. Soil having a pH value of 7.5 and containing 8.53 g· kg^ - 1 organic matter, 0.89 g· kg^ - 1 total N, 20.42 mg· kg^ - 1 olsen-P, 238mg· kg^ - 1 NH4OAcK, and 0.11 mg· kg^ - 1 Cd was used in the experiments. 15 kg of sieved soil was placed in each 36 cm × 42 cm pot. Fertilizers used were （NH4）2SO4,KNO3 and KH2PO4 .Prior to sowing 3 g of N,4.5 g of P2O5 and 9 g of K2O were applied to each pot. The cultivar used in the experiments was Yunyan 85, with 20 leaves left after topping. The liquid Cd（Ac）2 was applied to each pot as sewage with concentrations of 3,6,10,30,60 and 100 mg· kg^- 1 after transplanting. Clean water was used as comparison. The experiment was arranged in a completely randomized design with three replications. The net photosynthetic rate （Pn）, intercellular CO2 concentration （Ci） and stomatal conductance （ Gs ） of three identical functional leaves from the same position were determined during rosette, budding and harvest stages using a portable photosynthetic system （Li-6400） . Maximal fluorescence （ Fm）, fixed fluorescence （ Fo ）and steady fluorescence （Fs） were determined after 30- minute dark adaptation while maximal fluorescence in the light （Fm＇） was measured after a certain length of light period （Hansatech FMS2 fluorometer）. The same portion of each leaf was used for both kinds of measurements. PS 1] activity（ Fv/Fo）, PS Ⅱ maximum light energy transformation （Fv/Fm）, chemical quenching coefficient（qP）, non-photochemical quenching coefficient （ NPQ）, the apparent photosynthetic electron transport rate （ETR） and the ratio of photochemical quantum yield of PS Ⅱ （φPS Ⅱ） were calculated according to the following formulas： Fv / Fo = （Fm - Fo ） / Fo , Fv / Fm = （Fm - Fo ） / Fm , qP = （Fm＇ - Fs）/（Fm＇ - Fo）,NPQ = （Fm- Fm＇）/ Fm＇, φPS Ⅱ = （Fm＇ - Fs）/Fm＇,ETR = （Fm＇ - Fs）/Fm＇ × PAR × 0.5 × 0.84. The contents of reductive sugar, total N, nicotine and Kalium in tobacco leaves and yield per plant were determined according to standard methods in the literature. The results showed that the net photosynthetic rate （ Pn）, stomata] conductance （ Gs ）, PS Ⅱ activity （ Fv/Fo ）, PS Ⅱ maximum light energy transformation （Fv/Fm）, chemical quenching coefficient （qP）, non-photochemical quenching coefficient （NPQ）, the apparent photosynthetic electron transport rate （ETR） and the ratio of photochemical quantum yield of PS Ⅱ （ φPS Ⅱ ） decreased with the increase in Cd concentration, while intercellular CO2 concentration Ci） behaved oppositely. The fact that the reductive Sugar/Nicotine ratio and Total-N/Nicotine ratio increased as the result of enhanced Cd pollution, has led to inharmonious chemical constituents in tobacco leaves and unpleasant aroma from them.