不同烤烟品种幼苗形态结构及光合参数对 干旱胁迫响应机制的差异

为了比较不同烤烟品种的苗期耐旱性差异,选用河南烟区主栽烤烟品种‘豫烟6号’、‘豫烟10号’、‘豫烟12号’和‘中烟100’为供试材料,利用浓度为15%的聚乙二醇(PEG-6000)模拟中度干旱环境,研究不同烤烟品种幼苗生物量、根系形态、叶片气孔特征、叶绿体超微结构和光合参数等指标对干旱胁迫响应机制的差异。结果表明:(1)干旱刺激了幼苗根系生长,抑制了地上种幼苗根冠比均显著提高;‘豫烟6号’和‘豫烟12号’幼苗根系生物量、总根长、根系表面积和根系体积均显著增加,但根系平均直径与对照无显著性差异;而‘豫烟10号’和‘中烟100’根系形态指标增加幅度较小,仅有‘豫烟10号’根系表面积显著增加,而根系平均直径均显著下降。(2)干旱引起‘中烟100’叶片气孔总面积比对照显著增加,‘豫烟12号’仅有气孔长度比其对照增加显著。(3)干旱处理后,‘豫烟6号’和‘豫烟12号’叶绿体整体结构变化不大,而‘豫烟10号’和‘中烟100’中叶肉细胞叶绿体被膜分解,与细胞壁分离;其中‘中烟100’叶绿体平均长度、长宽比和面积均显著降低。(4)与对照相比,干旱组叶片光合作用被抑制,其中‘豫烟10号’和‘中烟100’叶片净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)均显著下降,而胞间CO2浓度(Ci)显著上升,说明干旱胁迫下烤烟光合速率下降是非气孔因素所致。(5)干旱胁迫后‘豫烟6号’和‘豫烟12号’叶片叶绿素总量显著增加,而‘豫烟10号’和‘中烟100’却呈下降趋势。结果表明,‘豫烟6号’和‘豫烟12号’是耐旱型品种,而‘豫烟10号’和‘中烟100’抗旱性较差,抗旱能力排序为‘豫烟6号’‘豫烟12号’‘豫烟10号’‘中烟100’。

Response of morphological structure and photosynthetic parameters to water deficit in four flue-cured tobacco cultivar seedlings

Drought is one of the many environmental factors which affect the growth and development of plants in many regions of the world due to climate change. The effect of moderate drought stress on seedling biomass, root morphology, stomatal characteristics, chloroplast ultra-structure and photosynthetic parameters of four flue-cured tobacco cultivars (Y6, Y10, Y12 and ZY100) were investigated in a hydroponic experiment with polyethylene glycol (PEG-6000) simulating moderate drought stress to evaluate drought tolerance of different flue-cured tobacco varieties. The results showed that the roots and leaves of different cultivars of tobacoo under moderate drought stress had different physiological responses. (1) A close relationship was noted between root growth and water supply in this study. The moderate drought stress stimulated root growth of flue-cured tobacco seedling, while it inhibited shoot growth. Root to shoot ratio of the 4 flue-cured tobacco cultivars significantly increased under drought stress conditions compared with that of control. Root biomass, total root length, root surface area and root volume of Y6 and Y12 significantly increased while root average diameter decreased. Then roots of Y10 and ZY100 were sensitive to moderate drought stress where root morphology index increased little or even decreased. Although the average diameter of the 4 flue-cured cultivars seedlings decreased significantly, root surface area of Y10 increased significantly. (2) Drought stress significantly decreased stomatal density while increasing both stomatal length and width of Y6, Y12 and Y10. There was a significant difference in stomatal density of ZY100 seedlings between the control group and the drought stress group. However, no significant difference was observed in stomatal width of the four flue-cured tobacco cultivars seedlings. Total pore area per leaf area of ZY100 significantly increased under drought stress. (3) Chloroplast ultra-structure of Y6 and Y12 was slightly changed under drought stress and the change was more obvious in Y10 and ZY100 cultivars. The shape of chloroplast in mesophyll cells changed and separated from cell wall, which destroyed chloroplast integrity. The average length, length-width ratio and area index of chloroplast decreased significantly for ZY100 seedlings under drought stress. (4) Net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) of the 4 cultivars seedlings declined, while intercellular CO₂ concentration (C_i) increased significantly in response to drought stress. This indicated that the decline in photosynthesis was as a result of the absence of stomatal restriction under moderate drought stress. The differences between drought group and control group were significant for Y10 and ZY100 seedlings. (5) Under drought stress, the chlorophyll contents of Y6 and Y12 increased significantly, while that of Y10 and Z100 increased slightly or even decreased. The comprehensive analysis showed that Y6 and Y12 were drought resistant cultivars, and Y10 and ZY100 were drought sensitive cultivars. Drought resistance ability of the 4 flue-cured tobacco cultivars was in the order of Y6 > Y12 > Y10 > ZY100 at seedling stage.