【作者】 彭强；

【导师】 梁银丽；

【作者基本信息】 西北农林科技大学 ， 生态学， 2010， 硕士

【摘要】 西北地区大部分处于干旱、半干旱地带,降水稀少,水资源短缺,已成为影响西北农业发展的一个关键因素。光照是植物进行光合作用的最重要能量来源,它可直接影响光合碳循环中光调节酶的活性,也可影响植物生长环境,如温度、湿度等来间接影响植物的生理生化过程。辣椒属耐弱光果菜,夏季晴天中午过高的太阳辐射极易导致光抑制现象,同时,辣椒根系较浅,再生能力弱,木栓化程度高,其生长期又正值高温季节,耗水量大,遮阴和水分供应就成为辣椒正常生长发育及果实成熟的关键因素。因此,研究遮阴和土壤水分对辣椒生长及叶片生理特性的影响,对于提高辣椒光能和水分利用效率,改善果实品质以及进一步了解辣椒对于光照和土壤水分逆境的抗性机制具有重要的理论和现实意义。本试验以辣椒为试材,在陕西杨凌西北农林科技大学水土保持研究所试验场内隔水小区中进行,2008年设计了4个土壤水分水平(土壤含水量分别为田间持水量(θ田)的40 %～55 %、55 %～70 %、70 %～85 %和85 %～100 %,分别用W1、W2、W3、W4表示)的随机区组试验,研究了土壤水分含量对辣椒生长、果实品质、干物质分配、水分利用效率(WUE)以及叶片光合生理特性和保护酶系统的影响;2009年设计了3个光照水平(分别为露地全自然光照、露地自然光照的70%和30%,分别用S0%、S30%和S70%表示)和4个土壤水分水平(同2008年水分设计)共12个处理组合的区组试验,分析了遮阴和土壤水分对辣椒果实生长和品质以及叶片生理特性的影响,优化确定出较佳遮阴和土壤水分组合,为大田生产中提高辣椒光能和WUE提供理论参考。主要研究结果如下:1.在土壤含水量为田间持水量的70 %～85 %条件下,同化物在地上和地下部分之间的分配更趋合理,产量最高,为6.05 kg·m-2;在土壤含水量为田间持水量的55 %～70 %条件下果实品质各项指标均达到最大值,其中Vc、游离氨基酸、可溶性总糖和可溶性蛋白质含量分别为1.16 mg·g-1、363.6 ug·g-1、19.4 mg·g-1、19.7 mg·g-1,此时WUE也最大,为28.66 kg·m-3,分别比W1、W3、W4提高了19.5 %,30.3 %和51.3 %。土壤含水量从田间持水量的70 %～85 %降低到55 %～70 %时,产量虽有一定的下降,但差异不显著,同时辣椒果实品质较优,水分利用效应较高,有利于节水。2.随着土壤含水量的减少,叶片叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)均相应降低,而游离脯氨酸和丙二醛(MDA)含量增加,Pn的下降主要是由气孔限制引起的;与W3处理相比,在W1、W2和W4处理下,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性均有不同程度的提高,表明叶片受到逆境伤害,产生应激反应,且CAT和POD的活性随土壤水分变化表现出相反趋势;WUE在土壤相对含水量为55%～70%时最大。在田间持水量的70 %～85 %条件下,辣椒叶片叶绿素含量较高,光合能力较强,同时叶片受伤害较小,不易早衰。3.自然光照及遮阴30 %条件下,随着土壤水分含量增加,叶干质量、茎干质量增加,而根干质量则呈下降趋势,辣椒果实果长、果径及单果重增加,但是,土壤含水量超过田间最大持水量的70 %～85 %,辣椒果实生长呈下降趋势;遮阴30 %、土壤相对含水量为55 %～70 %处理维生素C、可溶性糖,游离氨基酸和可溶性蛋白质含量均较其他处理高;在相同光照条件下,随着土壤水分含量的上升,耗水量上升,产量呈先升后降的趋势,适当的降低土壤含水量有利于WUE的提高;土壤水分相同,遮阴30 %利于产量的提高,减少无效水分消耗。遮阴70 %及土壤相对含水量为40 %～55 %条件下均不利于辣椒植株营养生长和果实形态建成。总的来看,遮阴30 %、土壤相对含水量为55 %～70 %条件下,能显著改善辣椒果实品质,提高WUE。4.随着遮阴程度和土壤水分的增加,叶片相对含水量(RWC),叶绿素含量均呈上升趋势,土壤水分增加主要有利于叶绿素a含量的增加,遮阴主要有利于叶绿素b含量的增加;类胡萝卜素含量随遮阴程度的增加和土壤水分的降低而下降;MDA含量在干旱胁迫条件(土壤相对含水量为40 %～55 %和55 %～70 %)下升高,随着遮阴程度的增加呈先降后升的趋势;光照相同,在干旱(土壤相对含水量为40 %～55 %和55 %～70 %)和高水(土壤相对含水量为85 %～100 %)条件下,保护酶活性和脯氨酸含量均表现出不同程度的上升,水分条件相同,保护酶活性和脯氨酸含量均随遮阴程度的增加而下降,且保护酶对光照强度的敏感性为SOD>CAT>POD;生理指标相关性分析表明,保护类物质(脯氨酸与保护酶)与伤害类物质(MDA)均达到了极显著正相关,膜保护酶与叶绿素含量达到了极显著负相关。在遮阴30 %和土壤相对含水量为70 %～85 %条件下,辣椒叶片RWC适宜,植株生长健壮;叶绿素、类胡萝卜素含量均较高,叶片光合潜力较大;MDA和脯氨酸含量较小,有利于SOD、CAT和POD活性的维持,叶片膜脂过氧化伤害较小。5.在自然光照和干旱胁迫(土壤相对含水量为40 %～55 %和55 %～70 %)条件下,净光合速率(Pn),Fv/Fm和Fv′/Fm′均呈降低趋势,而遮阴30 %则可以降低光化学伤害和光合系统Ⅱ(PSⅡ)的结构损伤,从而有利于辣椒果实有机质的积累;与其他处理相比,在遮阴30 %和土壤相对含水量为70 %～85 %的条件下,辣椒叶片叶绿素相对含量、光合能力和叶绿素荧光均较高;在遮阴70 %条件下,Fv/Fm和Fv′/Fm′虽有所增加,但是叶片光合能力和光子通量密度均显著降低。Pn,Fo和Fv/Fm光照和水分互作达到了显著性差异,其他指标互作效应不明显。总体来看,遮阴30%和土壤相对含水量为70 %～85 %条件下叶片叶绿素含量较高,PSⅡ反应中心受到的伤害较小,光合能力较强。更多还原

【Abstract】 Most of the Northwest regions in the arid and semi-arid zones, where precipitation is scarce while evaporation capacity is 4 to 10 times more than that of the precipitation. Therefore, water shortage is significant, which has become a key factor in Northwest agricultural development. Light is the most important energy source for photosynthesis of plants, which directly affects the activities of photosynthetic enzymes in the carbon cycle and also affects plant growth environment, such as: Temperature, humidity which indirectly influences the plant’s physiological and biochemical processes. Pepper is a weak light-resistant fruit and vegetable and light saturation point is only 30klx, so solar radiation can easily lead to the phenomenon of photoinhabition in sunny summer afternoon. In addition pepper is shallow roots plants, which has weak regenerative capacity and a high degree of cork, the growing season is high water-consumption in high-temperature season. Therefore, shade and water supply will become critical factors in pepper’s normal growth fruit ripening period.Pepper was studied in this paper in Institute of Soil and Water Conservation District conducted test sites, Northwest A & F University, Yangling, Shaanxi. In 2008, four soil moisture levels (soil water holding capacity, respectively) were designed as 40% to 55%, 55% to 70%, 70% to 85% and 85% to 100%, respectively signed W1, W2, W3, W4 ) in randomized block experiment. The influences of soil water content on the growth of pepper, fruit quality, dry matter distribution, water use efficiency, leaf photosynthetic characteristics and protective enzyme system were studied; In 2009, group tests were designed as three light levels (open field full of natural light, exposed to natural illumination 70% and 30%, respectively signed S0%, S30% and S70% ) and four soil moisture levels (water with the 2008 design) with 12 treatment combinations. The affects of the shading and soil moisture on growth and pepper quality and physiological characteristics of leaves were analysed.The best combination of shade and soil moisture for the field was confirmed through the tests, which provided a theoretical reference to improve the production of solar energy and water use efficiency of pepper. The major results are as follows:The highest output was 6.05 kg·m2 and the assimilations of distribution on the ground and the underground sections was more reasonable.in the field capacity of soil moisture content 70 %—85 % conditions. When soil water was account for 55 %—70 % of the field capacity, quality indicators reached to the maximum .Vc was 1.16 mg/g, free amino acids was 363.6 ug·g, soluble sugar was 19.4 mg·g and soluble protein was 19.7 mg·g respectively. While water utility efficiency in the conditions was also the largest (28.66 kg/m3), respectively increased 19.5 %, 30.3 % and 51.3 % to compare with W1, W3, W4.The production of pepper had some decline because of soil moisture decline from field capacity of 70% ~85% to 55% ~ 70%, but the difference was not significant. Meanwhile pepper quality was better and WUE was higher so as to save water.with the reduction of soil moisture, SPAD readings, Pn, Gs, Ci and Tr depressed accordingly showing a clear positive correlation, howover, free proline and MDA content were on the rise,the decrease of net photosynthetic rate was considered as a result of stomatal restriction;Under W1、W2 and W4 treatment the activity of SOD,CAT and POD increased respectively to a certain extent compared with the W3 treatment indicated that: leaf damage by adversity resulted in stress response and CAT and POD activity were almost presented opposite trends by comparison with the change of soil moisture; The WUE was highest in 55-70% of field capacity.In the condition of 70% -85% field capacity, pepper chlorophyll content was higher and photosynthetic capacity was more effective .Meanwhile leaves were little injured and were not easy to premature senility.With the increase of soil water content, leaf relative water content, leaf dry mass and stem mass increased, while root dry mass was a declining trend, pepper fruit length, fruit diameter and fruit weight increased in natural light and shade 30%, but pepper fruit growth showed a downward trend in soil moisture content exceeding field maximum moisture holding capacity of 70-85%;Moderate shade and reduce soil moisture content are benefit for increasing fruit quality, which vitamin C, soluble sugar, free amino acids and soluble protein content in S30%W2 are higher than in other treatments; With the increase in soil moisture content, water consumption increased, the output was first increased and then falling trend in the same light conditions, and the appropriate reduction in soil moisture is conducive to the improvement of water use efficiency; the same soil moisture and moderate shade are conducive to enhance productivity and reduce invalid water consumption. Deep shade and extreme drought stress are not the use of pepper plant vegetative growth and fruit morphogenesis.Through comprehensive analysis, pepper fruit quality was significantly improved and WUE was increased in the condition of 30% shade and 55-70% relative soil water content.With the increased of shade and soil moisture levels, leaf RWC, chlorophyll content were on the rise. The increased of soil moisture was mainly beneficial to the increase of chlorophyll a, Shade was good to the increase of chlorophyll b; Carotenoids declined with the increase of shade and the decline of soil moisture; MDA content increased under drought stress, and it declined then increased with the increase of shade. In the same light, protective enzymes activity and proline content showed degrees of increase. In the same moisture conditions, protective enzyme activities and proline content were decreased with the increased of the shade, and the protective enzyme sensitivity to light intensity is:SOD> CAT> POD. Physiological correlation analysis showed that praline, protection of enzymes and MDA have reached a very significant positive correlation. Chlorophyll content and membrane protective enzyme reached a highly significant negative correlation. In the condition of shading 30% and 70%-85% relative soil water content, pepper leaves RWC was suitable and plants were robust; chlorophyll and carotenoid contents and leaves photosynthetic capacity were higher; MDA and proline content were less which was favorable to maintain the activities of SOD, CAT and POD, so the membrane lipid peroxidation was little injuried.The results indicated that pepper plants underwent photochemical damage due to decrease in Pn and in the ratio of variable to maximal fluorescence (Fv/Fm and Fv′/Fm′) in full sun-light (0% of shade degree) condition, especially under 40-55% and 55-70% of field moisture capacity. In contrast, appropriate shading can decrease photochemical damage and structural damage to the PSII reaction center complex so that profit the carbon accumulation of fruit. 30% shade-induced plants displayed high relative chlorophyll content, photosynthesis capacity and chlorophyll fluorescence during the reproductive stages, especially under 70-85% of field capacity, however, 70% shade-induce plant presented lowest photosynthesis capacity, qP and NQP indicating there was low photosynthetic photon flux density although Fv/Fm and Fv′/Fm′increased slightly. Furthermore, shade degree×water interactions were significant in Pn, Fo and Fv/Fm, but no significant in other parameters.Conclusively, in the condition of shading 30% and 70%-85% relative soil water content chlorophyll content was higher and PSⅡreaction center was suffered less damage, leaves photosynthetic capacity was superior.更多还原