【作者】 韩炜；

【导师】 刘西平；

【作者基本信息】 西北农林科技大学 ， 植物学， 2009， 硕士

【摘要】 本文以一年生刺槐(Robinia pseudoacacia)幼苗为实验材料,采取盆栽方式,研究其光合特性对不同土壤水分条件的响应及其变化规律,探讨水分胁迫下的生理适应机制。实验设置3种土壤水分处理(土壤最大持水量的70%、55%、40%),分别表示对照、轻度水分胁迫和严重水分胁迫。结果表明:(1)水分胁迫显著抑制了刺槐的株高生长和地径生长,且随着胁迫程度加剧株高、地径受到抑制程度增加。(2)随着水分胁迫的加大刺槐的光饱和点(LSP)、最大净光合速率(Amax)、表观量子效率(AQY)逐渐降低,光补偿点(LCP)、暗呼吸速率(Rd)呈升高趋势,表明水分胁迫使刺槐的光合能力降低,对光强的应用范围变窄,对光环境的适应能力降低。不同水分处理下刺槐的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)及水分利用率(WUE)对光合有效辐射(PAR)的响应均表现为:对照处理>轻度水分胁迫>严重水分胁迫,Pn、Gs及WUE对光照强度的变化具有明显的阈值响应。(3)随着水分胁迫加剧,净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间二氧化碳浓度(Ci)均呈下降趋势。各处理间刺槐水分利用率(WUE)在9:00-17:00之间区别不是很明显,其日变化趋势与净光合速率(Pn)日变化相似。(4)随着土壤水分胁迫的加剧,叶片的叶绿素a(Chl a)、叶绿素b(Chl b)含量下降,但类胡萝素(Car)含量表现为:轻度水分胁迫>严重水分胁迫>对照处理,起到一种光保护作用。(5)水分处理显著降低了PSⅡ系统最大量子产量(Fv/Fm)、非循环光合电子传递速率(ETR)表明PSⅡ活性中心受水分胁迫的影响,光合原初反应中电子传递过程受阻。PSⅡ实际量子产量(Yield)也随水分减少而减少,同时其日动态变化反映了PSⅡ反应中心的光化学活性可逆失活变化过程。ETR对PAR的响应均表现为先增后减趋势且对照处理>轻度水分胁迫>严重水分胁迫,同时对照处理的ETR最高点出现在PAR为1300μmol·m-2·s-1,而轻度水分胁迫和严重水分胁迫的ETR达到最高时PAR大约为800mol·m-2·s-1。叶绿素荧光的光化学淬灭随水分胁迫的加重逐渐降低,而非光化学淬灭逐渐上升。(6)不同土壤水分条件下韧皮部蔗糖的运输速率不同,并随着水分胁迫的加剧而降低。(7)不同水分处理下刺槐叶、茎、粗根中还原性糖含量随着水分胁迫的加剧逐渐升高。叶片中蔗糖的含量随着水分胁迫的加剧而增加,茎和粗根中蔗糖含量随水分的含量的降低而下降。刺槐各个部位总的可溶性糖含量均随水分含量的减少而上升,各处理之间差异显著。不同水分条件下叶、茎、粗根中淀粉含量的变化具有明显的规律性,均随着水分胁迫加剧而减少。更多还原

【Abstract】 Robinia pseudoacacia seedlings were used in the study to investigate the influence of different soil contents on photosynthetic characteristics and the underlying mechanism as well as the adaptability of their physiological mechanism to water stress. The three kinds of soil moisture treatment condition were adopted with the maximum field capacity for holding water being 70%, 55% and 40%, which simulated the environment conditions with no water stress, mild water stress, and severe water stress respectively. The results indicated that,(1) Water stress significantly inhibited the growth of the plant height and diameter of stem base of Robinia pseudoacacia. The plant height and diameter of stem base was inhibited with the increasing degree of water stress.(2) Along with the increase of water stress, there was a trend to decrease in light saturation point (LSP), maximum photosynthetic rate (Amax) and apparent quantum yield (AQY), but a trend to increase in light compensation point (LCP) and dark respiration rate (Rd). The results reaveled that water stress led to series responds of robina pseudoacacia, which included narrowing the range of photosynthetic active radiation, decreasing the photosynthetic capability and the adaptability. Under different soil conditions, the impact of Pn, Gs, Tr and WUE on PAR are determined to be check, mild water stress and severe water stress respectively. Changes in light intensity are also found to play a significant role in threshold responses of Pn, Gs, and WUE.(3)With the increase of water stress, daily variation in net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentration (Ci) of Robinia pseudoacacia were indicated a trend to decrease. The difference of variation in water use efficiency (WUE) beween different water stress are not significant during the period of the day from 9 a.m. to 5 p.m., which shared the same trend of daliy variation net photosynthetic rate (Pn).(4)As water stressing increased, concentration of Chlorophyll a (Chl a) and Chlorophyll b(Chl b) of leaves have decreased. However, Carotenoid (Car) concentration was highest in mild water stress, then in severe water stress and the least in check, indicating a protective role against light.(5)Water treatment led to a significant decrease in the efficiency (Fv/Fm) of the primary conversion of light energy in the reaction center of photo system II(PSⅡ), and of the non-cycle photosynthetic electron transport rate (ETR). This showed that the active sites in photo systemⅡwere inhibated by water stress, and the process of electron transfer in primary photosynthetic reactions was discouraged by this stress. Simultaneously, quantum yield of PSⅡelectron transport (Yield) in photo system II was reduced with the water stress increasing, and the process of reversible deactivation in the reaction center of photo systemⅡwas reflected by its daily dynamic variations. The impact of ETR showed an increase followed by a decrease of PAR with the following results of check, mild water stress and severe water stress respectively. And when ETR reached the highest point, the PAR in check was 1300μmol·m-2·s-1 with 800μ·m-2·s-1 in mild and severe water stress. With the increase of water stress the photochemical chlorophyll fluorescence quenching decreased, but the non-photochemical quenching gradually increased.(6) The transportation velocity of saccharose in phloem are different among different soil moisture condition, and with the increased water stress, the velocity decreased.(7)The concentration of reduced sugar in leaves, stems and thick roots of Robinia pseudoacacia increased gradually with the increase of the water stress. Saccharose conentration in leaves increased largely with increased water stress, but decreased in stem and thick root. With the increase of the water stress the concentration of soluble sugar in all tested organs of Robinia pseudoacacia increased, with the significant difference between each water stress treatment. The tests on leaves, stems and thick root indicated that along with the increase of water stress, the starch content reduced.更多还原