【作者】 杨启良；

【导师】 张富仓；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2009， 博士

【摘要】 当前面临着水资源危机和环境恶化的突出矛盾,通过减少灌溉用水和提高植物适应环境胁迫能力来维持干旱半干旱地区生态系统平衡是众多学者十分关注的重要问题。近年来,有关植物水分传导、水流阻力和其它生理要素对各种环境因素的响应特征及规律的研究一直是许多学者十分关注的热点研究领域,特别是近些年出现的“控制性根系分区交替灌溉”技术的广泛研究和应用,确实对改善植物生长的土壤水分状况,提高灌溉水分利用效率起到了重要的作用。在果树分布较多的干旱半干旱地区,农田水分和养分与盐分胁迫并存,对果树的生长产生很大的影响,研究控制性分根交替灌溉和环境因素对苹果幼树水分传输的影响对于丰富果树水分传输理论以及节水调控机制具有重要的理论和实际意义。论文以红富士苹果幼树为材料,通过盆栽和田间小区实验相结合的方法,系统地研究和分析了部分根区滴灌和环境因素对苹果幼树水分传输机制的影响,取得了以下重要结论:1.根区滴灌模式和水分处理对苹果幼树生长和根系水分传导的影响表明:根系水分传导与根干重和叶水势均呈正相关关系。交替灌溉反复刺激根系较快生长是根系水分传导提高的重要原因。同时采用交替滴灌模式有利于优化干物质向各个器官均衡分配,使其茎粗/株高和根冠比增大,使得壮苗指数大大提高。从而增强了植物根源水力信号的传输效率和调控植物水分平衡的能力。根系生长和根系水分传导随着土壤水分含量的增加而增大,当灌水定额由20 mm增大到30 mm时,交替滴灌处理的根系水分传导增幅最大,表现为:ADI(17.34%)>FDI(12.27%)>CDI(3.36%)。在平均节水达33%时,交替滴灌处理的平均侧根干重和根系水分传导分别较常规滴灌仅降低了19.1%和5.81%,而茎粗/株高、根冠比和壮苗指数分别提高了0.27%、19.46%和11.74%。交替滴灌处理的生长状况和根系水分传导均高于固定滴灌。2.根区滴灌方式和水分处理对苹果幼树水流阻力有显著影响。相关性分析表明,叶水流阻力与气孔导度呈负相关关系,而与叶面积呈正相关关系。交替滴灌提高了叶水流阻力是降低蒸腾失水的重要因素,加之降低了根系阻力和(侧枝+主杆)阻力,从而提高了苹果幼树贮水和渗透调节能力及抗干旱胁迫能力。因此,交替滴灌提高了对环境的适应能力。苹果幼树根系阻力、冠层阻力、(侧枝+主杆)阻力和单株阻力随着灌水量的增大而减少,而(叶+柄)阻力随着灌水量的增大而增大。在20 mm和30 mm灌水定额下,交替滴灌的(叶+柄)阻力分别比常规滴灌提高17.89%和24.58%。在平均节水达33%的前提下,交替滴灌和固定滴灌的平均(叶+柄)阻力分别比常规滴灌提高了19.65%和24.34%,但交替滴灌和固定滴灌的平均(侧枝+主杆)阻力分别降低了4.61%和13.02%。部分根区滴灌方式通过减小苹果气孔导度和叶面积,提高(叶+柄)阻力,从而减少了叶片的蒸腾失水,提高了苹果幼树的水分利用效率。通过研究不同器官水流阻力及占全株的比例发现,根系阻力占全株水流阻力的比例最大,达62.28%,其次为冠层阻力,占37.72%,(叶+柄)阻力及(侧枝+主杆)阻力分别占19.9%和17.82%。可见,根系是阻碍水分传输的主要器官,叶片是阻碍冠层水分散失的主要器官。3.部分根区滴灌方式和水分处理对苹果幼树生理特性和水分利用效率的影响表明:在节水达33.3%时,交替滴灌和固定滴灌处理的平均根系水分传导仅降低了5.81%和14.7%,但总水分利用效率、灌溉水利用效率分别高出了常规滴灌处理达16.31%和14.48%、40.52%和27.65%,说明部分根区滴灌方式处理后根系水分传导的提高是引起水分利用效率提高的一个重要方面。4.部分根区滴灌下苹果幼树茎液流和水分传导日季节变化及其与环境因素的关系表现为:(1)苹果幼树各器官水分传导均存在明显的季节变化,随着生长季节的推移,根系水分传导、冠层水分传导、(主杆+侧枝)水分传导和(叶+柄)水分传导的变化趋势均为先增加后减小;而主杆水分传导和侧枝水分传导随着生长季节的推移逐渐增大。(2)根系水分传导日变化过程曲线拟合结果为二次抛物线方程,各滴灌处理均在12:00左右时取得最大值,且常规滴灌处理的值最高;在18:00左右取得最小值,且固定滴灌处理的值最小;各处理在16:00左右时其值又恢复到8:00左右的水平。三种滴灌方式下,(叶+柄)水分传导的日变化过程均表现为双峰型,分别在12:00和16:00取得峰值,(叶+柄)水分传导最大值在12:00时取得,(叶+柄)水分传导最小值在14:00取得。三种滴灌方式在两次峰值的大小顺序均表现为,CDI> ADI> FDI。(3)冠层各器官水分传导与它对应的干物质呈线性正相关关系。主杆水分传导与其干重具有较高的相关系数,说明用主杆干重能较好的衡量它的导水能力,其方程式为:kmr= 0.5406Wmr + 0.9721,R2 = 0.6377。根系水分传导与根区土壤含水量和土壤温度均呈线性正相关关系,部分根区滴灌方式提高了根区土壤温度也是引起根系水分传导提高的一个重要因素。在不同测定时期,根系水分传导与根区土壤含水量的决定系数大小关系为:R2(8月)(0.6949)>R2(10月)(0.5391)>R2(6月)(0.1551)>R2(12月)(0.0428),分别在8月和12月取得最大值和最小值。说明根系水分传导与根区土壤含水量的关系与季节变化密切相关。(4)在不同的天气状况下,常规滴灌处理的茎液流量均显著的大于交替和固定滴灌处理;不同滴灌方式下,苹果幼树茎液流季节变化趋势与大气温度的变化相关。无论是晴天,还是雨天,各处理的茎液流昼夜变化均表现为单峰曲线,当天气为多云时,茎液流昼夜变化起落较大表现为多峰曲线;部分根区滴灌下苹果幼树茎杆水分传导与日茎液流量呈线性正相关关系,相关系数大小关系表现为,CDI(0.9806)>ADI(0.9275)>FDI(0.8173)。5.部分根区滴灌和施肥处理对苹果幼树导水特性的影响表明:在交替滴灌和固定滴灌处理较常规滴灌处理节水达50%的条件下,与无肥处理相比,交替滴灌处理促进根系生长的幅度较常规滴灌处理大,但叶干重的降幅较大。这样交替滴灌处理的植株保持较低的每单位吸收面积的蒸腾速率。交替滴灌根系水分传导的提高是引起水肥利用效率提高的重要原因,不仅提高了节水调控能力,而且也提高了水肥传输能力。虽然常规滴灌处理的平均根系水分传导均高于交替滴灌和固定滴灌处理,但与无肥处理相比,平均增幅大小顺序为,ADI(5.14倍)>CDI(4.74倍)>FDI(4.04倍),说明施肥后对交替滴灌处理的根系水分传导的影响最大。交替滴灌和固定滴灌的蒸腾量和蒸散量分别较常规滴灌处理降低了34.4%和71.27%。交替滴灌处理的生长状况和根系水分传导均高于固定滴灌。苹果幼树生长和壮苗指数及根系水分传导均随着施肥量的增大而提高。与无肥处理相比,在三种滴灌方式处理下,平均根系水分传导增长倍数的大小顺序依次为:N2P2(7.37倍)>N1P1(6.7倍)>P2(4.82倍)>P1(3.72倍)>N2(2.98倍)>N1(2.11倍);氮磷配施促进幼树较快生长,根系水分传导大大提高,使得干物质向各个器官均衡分配,提高了壮苗指数。从单施肥的效果来看,施氮促进冠层较快生长,施磷促进根系较快生长,使得根系水分传导较施氮显著提高,虽然施磷减小了总干物质量,但因施磷对根冠比和粗高比的提高幅度较大,因此,施磷也提高了壮苗指数。可见,将交替滴灌与施肥处理相结合,其有利作用可以得到更好地发挥。6.盐分处理对部分根区滴灌的苹果幼树生长和水分传导有显著影响。交替和固定滴灌处理干燥侧根系阻碍了对盐分离子的吸收,从而减小了盐分离子对根系的伤害。交替和固定滴灌处理在减少50%灌水量条件下,与常规滴灌相比,在高盐分S2和S3处理下交替滴灌处理的叶水分传导分别较常规滴灌降低了33.56%和44.26%,但交替滴灌处理的根系水分传导反而提高了1.13%和10.91%。交替滴灌处理的苹果幼树生长和水分传导均高于固定滴灌处理。可见,采用交替滴灌处理后不仅提高了苹果幼树根源水力信号的传输效率和调控水分平衡的能力,而且也提高了抗盐分胁迫能力。随着盐分浓度的增大,虽然幼树生长受阻,光合速率,气孔导度和蒸腾速率大大降低,水分传导明显减小,但对交替滴灌处理的影响较小。当盐分浓度由S1增大到S2再到S3时,与对照处理相比,三种滴灌方式处理下的根系水分传导和叶水分传导平均降幅顺序为,CDI(48.06%和38.18%)>ADI(40.57%和29.65%)>FDI(32.82%和21.22%)。可见,盐分胁迫对常规滴灌处理的导水能力影响最大。幼树各器官水分传导与其干物质的关系表明,根系水分传导与侧根干重间均呈对数关系,而其它各器官水分传导与其干重间均呈线性正相关关系,但叶片水分传导与叶干重和气孔导度间呈乘幂关系。从以上分析可以得知,植物的水分传导与植物的生长环境密切相关,在果树节水灌溉中,采用根系分区交替灌溉方式,不但有利于调节果树根系和冠层的生长,优化干物质向各个器官均衡分配,使其茎粗/株高和根冠比增大,使得壮苗指数明显提高,而且对果树水肥的吸收和传输产生较大的影响。交替灌溉引起根系水分传导提高的重要原因是反复刺激根系较快生长,同时交替滴灌处理的植株保持较低的每单位吸收面积的蒸腾速率,从而对水肥利用效率的提高和调控冠层部分的水分消耗起重要的作用。可见,采用根系分区交替灌溉方式有利于提高对环境的适应能力及节水调控能力,不仅在干旱半干旱地区,而且在盐碱地区也有广阔的应用前景。更多还原

【Abstract】 In face of the prominent problems of the current water crisis and environmental degradation, how to reduce the amount of irrigation water and improve water use efficiency of plants in itself to maintain the arid and semi-arid ecosystem balance will be a crucial question in future. In recent years, there are some hot research projects about the response of the plant water hydraulic conduction, hydraulic resistance and other physiological elements to a variety of environmental factors. Especially, partial root-zone alternate drip irrigation which is widely studied and applied indeed plays an important role in improving the relationship between soil water condition and in enhancing the water use efficiency of irrigation. In our country the majority of orchards are located in arid and semi-arid regions. The contradiction of nutrient supply and salt stress of soil is outstanding and these two factors always have an important influence on fruit trees. Thus, the studies on the root water uptake and water transport in plants in this condition not only enrich the water transport theories, but also have significances in determining the regulation mechanism of partial rootzone irrigation and in providing services to the orchards production in water shortage regions.In this paper,young apple tree is used as experimental material. Partial root-zone alternate drip irrigation and the response of the environmental factors on the mechanism of water transport are studied and analysed systematicly by pot and field plot experiments. The main conclusions are showed as follow:1. By studying effects of different drip irrigation patterns of root zone and watering treatments on young apple tree growth and root hydraulic conductivity, it shows that there is a positive correlation between root hydraulic conductivity and root dry mass and water potential. partial root-zone alternate drip irrigation repeatedly stimulates root rapid growth are important reasons for the increase root hydraulic conductivity. Using partial root-zone alternate drip irrigation pattern may help to optimize dry matter even distributed to every organs, increase its ratio of stem diameter and plant height and root-shoot, so seedlings healthy index is greatly enhanced. Thus, strengthened the roots to absorb and transport watering capability which impelled the transmission efficiency of root hydraulic signal and the ability of regulating water balance of seedling could be enhanced.Root biomass and root hydraulic conductivity could be enhanced by increasing the amount of irrigation. When the irrigation quota increased from 20 mm to 30 mm each time, root hydraulic conductivity of partial root-zone alternate drip irrigation treatment has the largest increase, shows: ADI(17.34%)>FDI(12.27%)>CDI(3.36%). When the amount of irrigation water in partial root-zone alternate drip irrigation treatment is saved by 33% , dry mass of lateral roots is only reduced by 6.33%, but the ratio of stem diameter and plant height, and root-shoot ratio , seedlings healthy index are enhanced by 0.27%, 19.46% and 11.74% respectively. Alternate drip irrigation treatment of growth conditions and root hydraulic conductivity are higher than the fixed drip irrigation.2. By studying effects of drip irrigation patterns of partial root zone and watering treatments on young apple tree hydraulic resistance, it shows, Correlation analysis shows, there is a negative correlation between and leaf stomatal conductance, while there is a positive correlation between hydraulic resistance and leaf area. The increase of leaf hydraulic resistance under alternate drip irrigation treatment play an important role in reducing water loss of leaf transpiration, and By decreasing root resistance and resistance of lateral branch and master rod, thus the partial rootzone irrigation raises crop storage water adjustment function , enhances the capacity of osmotic adjustment and increases the resistant ability to drought. So the alternate drip irrigation enhances the capacity of the environment adaptability.The root resistance, shoot resistance, resistance of lateral branch and master rod of young apple tree are decreased by increasing watering quantity, while the resistance from leaf to petiole are raised by increasing watering quantity. In 20 mm and 30 mm irrigating quota, the hydraulic resistance from leaf to petiole of alternate drip irrigation were increased by 17.89% and 24.58% respectively compared with that of conventional drip irrigation treatment. In the premise of saving 33% of the water supply, compared with conventional drip irrigation treatment, the average hydraulic resistance from leaf to petiole in alternate drip irrigation and fixed drip irrigation are increased by 19.65% and 24.34% respectively, but the average resistance of lateral branch and master rod are reduced by 4.61% and 13.02%, respectively. For the reason that the partial rootzone irrigation increases the hydraulic resistance from leaf to petiole through the decrease of the stomata conductance, leaf area, and thus decreases the leaf blade luxurious transpiration dehydration, and raises plant’s water use efficiency.Hydraulic resistances of different components and their contributions to whole-plant resistance by studying show: Root resistance to account for the largest proportion of whole-plant resistance, accounting for 62.28 %, followed by shoot resistance, accounting for 37.72%, in turn resistance from leaf to petiole and resistance of lateral branch and master rod, accounting for 19.9% and 17.82%, respectively. So it shows that within the hydraulic resistance of each organ in the whole plant, the root system is the main organ of hindering water transport and leaves is the main organs of hindering water consumption.3. By studying effects of different drip irrigation patterns of root zone and watering treatments on young apple tree physiological characteristics and water use efficiency, it shows that when ADI and FDI save 33.3% of irrigation water the average root hydraulic conductivity only reduce 5.81% and 14.7%, but the average total water use efficiency and irrigation water use efficiency are enhanced by 16.31% and 14.48%、40.52% and27.65% respectively, which indicates that root hydraulic conductivity plays an important role in improving water use efficiency under partial root-zone irrigation strategies.4. By analyzing daily and seasonal changes of young apple tree stem sap flow and hydraulic conductivity and its relationship with environmental factors under partial root zone irrigation, some conclusions are obtained:(1) Hydraulic conductivity in each organs of young apple tree have a obviously seasonal variation. With the growing season goes on, the variation trend of root hydraulic conductivity, shoot hydraulic conductivity, hydraulic conductivity of lateral branch and master rod, and hydraulic conductivity from leaf to petiole increase at first and then decrease; while the trend of master rod hydraulic conduction, lateral branch and master rod hydraulic conduction gradually increase with the growing season goes on.(2) The curve fitting result of daily changes of root hydraulic conductivity is a quadratic parabolic equation. All drip irrigation treatments have a Maximum value at around 12:00 and the Maximum value of daily root hydraulic conductivity in the conventional drip irrigation is obtained; at around 18:00 the minimum value is obtained and it is appeared in fixed drip irrigation treatment; when its value go back to the level of 8:00 at about 16: 00. Under three drip irrigation patterns, daily change of the hydraulic conductivity from leaf to petiole is shown as a bimodal curve and it obtains its peak at 12:00 and 16:00 respectively. Maximum value of the hydraulic conductivity from leaf to petiole is obtained at 12:00 and the minimum is obtained at 14:00. Under three drip irrigation patterns, the maximum and minimum values decrease in order of its performance: CDI> ADI> FDI.(3) There is a positive correlation between shoot hydraulic conductivity of its each organs and its corresponding dry matter. The master rod hydraulic conduction and its dry weight have a high correlation coefficient showing that the master rod dry weight can be a better factor to estimate its hydraulic conduction capacity and the formula is: kmr = 0.5406Wmr + 0.9721, R2 = 0.6377. There is a linear positive correlation between root hydraulic conductivity and root zone soil moisture and also soil temperature showed a positive correlation with root hydraulic conductivity. That the partial root zone drip irrigation pattern improves the root zone soil temperature also plays an important role in enhancing root hydraulic conductivity. At different measured time, the relationship of the decision coefficient of root hydraulic conductivity and root zone soil moisture is: R2(Aug)(0.6949)>R2(Oct)(0.5391)>R2(Jun)(0.1551)>R2(Dec)(0.0428). It obtains the maximum and minimum values in August and December respectively. Thus, there is a close relationship between root hydraulic conductivity and root zone soil moisture relations, seasonal changes.(4) In different weather conditions, the stem sap flux of conventional drip irrigation treatment is significantly greater than the other two treatments; Under different drip irrigation patterns, the seasonal variation trends of young apple tree stem sap flux are related to atmospheric temperature seasonal variation. No matter it is sunny days or rainy days, the stem sap flow diurnal variation of each treatment show a single peak curve, but the diurnal variation of stem sap flux show a multi-peak curve when the weather becomes cloudy. It shows that there is a positive correlation between stem hydraulic conductivity and diumal stem sap flux, the relationship of their correlation coefficient is: CDI (0.98) > ADI (0.93) > FDI (0.82).5.By analyzing effects of drip irrigation patterns of partial root zone and fertilization treatments on hydraulic conductivity characteristics of young apple tree, we achieve the following conclusions: in the premise of saving 50% of irrigation water by alternate drip irrigation and fixed drip irrigation compared with conventional irrigation treatment and compared with no fertilizer treatment , root growth rate of alternate drip irrigation treatment is higher than conventional drip irrigation treatment, but leaf dry weight of alternate drip irrigation treatment have a larger drop. Thus alternate drip irrigation treatment’s plants can maintain the lower transpiration rate of per unit absorbing area. Root hydraulic conductivity plays an important role in improving water and fertilization use efficiency under alternate drip irrigation treatment, not only enhances the capacity of water-saving regulation and control, but also improves the water and fertilization transmission capacity.Although the average root hydraulic conductivity of the conventional drip irrigation treatment is higher than alternate drip irrigation and fixed drip irrigation, the average root hydraulic conductivity shows decreases in this order compared with no fertilizer treatment: ADI(5.14 times)>CDI(4.74 times)>FDI(4.04 times).This indicates that effects of fertilization on alternate drip irrigation treatment is the largest. Transpiration and evapotranspiration of alternate drip irrigation and fixed drip irrigation treatment reduce 34.4% and 71.27% respectively compared with the conventional drip irrigation treatment. Growth condition of alternate drip irrigation treatment and root hydraulic conductivity are higher than the fixed drip irrigation.With the increase of the amount of fertilizer, seedling growth, healthy index of seedling and root hydraulic conductivity improves. the average root hydraulic conductivity of three drip irrigation patterns shows decreases in this order compared with no application fertilizer treatment: N2P2 (7.37 times) >N1P1 (6.7 times) >P2 (4.82 times) >P1 (3.72 times) >N2 (2.98 times) >N1 (2.11 times). Application of mixture of nitrogen and phosphorus promotes rapid growth of young apple tree and increases the root hydraulic conductivity greatly, makes the dry matter to distribute more balanced to each organs, improves the healthy index of seedling. Judging from the effect of single fertilization,application nitrogen promotes fast shoot growth and application phosphorus promotes root rapid growth, making the root hydraulic conductivity improves more significant than only application nitrogen. Although application phosphorus reduces the amount of total dry matter, the phosphorus has a positive effect on the root-to-shoot and diameter-high ratio larger, so application phosphorus also increases the healthy index of seedlings. It can clearly be seen that the beneficial effect of alternate drip irrigation should be better materialized under appropriate fertilization.6. By analyzing effects of drip irrigation patterns of partial root zone and salt treatments on growth and root hydraulic conductivity of young apple tree. Results shows that the dry root zone of alternate drip irrigation and fixed drip irrigation treatment hinder the absorption of salt ions, which reduces the damage of salt ions to the root system. Compared to CDI treatment, ADI and FDI treatment reduced irrigation water by 50%. Under higher NaCl concentrations (S2 and S3) levels, ADI treatment decrease from leaf to petiole hydraulic conductivity by 33.56% and 44.26%, while the root hydraulic conductivity of alternate drip irrigation treatment increased by 1.13% and 10.91%, respectively. At the same time,the growth and hydraulic conductance of alternate drip irrigation treatment are all higher than fixed drip irrigation treatment.This indicates that the root hydraulic signal transmission efficiency of alternate drip irrigation treatment, the ability of seedlings regulating water balance and resistance stability to salt-stress could be enhanced.With the increase of the salt concentration, the young apple tree growth blocked, photosynthetic rate, stomatal conductance and transpiration rate are greatly decreased, hydraulic conductivity significantly reduced. However, alternate drip irrigation treatment is less affected. As the salt concentration increased from S1 to S2 to S3 and compared with no salt treatment,the average decreasing range of root hydraulic conductivity and from leaf to petiole hydraulic conductivity under three drip irrigation patterns shows: CDI (48.06% and 38.18%) > ADI (40.57% and 29.65%) > FDI (32.82% and 21.22%). The relationship between hydraulic conductivity of young apple tree and their dry matter shows that there is a logarithmic relationship between them, but the relationship between other organ’s hydraulic conductivity and its dry weight shows a linear positive correlation, however, it shows that there is a power relations between from leaf to petiole hydraulic conductivity and leaf blade dry weight and stomatal conductance.From the above analysis, we know that hydraulic conductivity of plants is closely related to the environment in which plants grows. water-saving irrigation in fruit trees, using alternate partial rootzone irrigation patterns not only helps to regulate roots and shoots growth of fruit trees and optimize dry matter even distributed to every organs, increase its ratio of stem diameter and plant height and root-shoot, so seedlings healthy index is greatly enhanced, but also has a greater impact on fruit water and fertilization absorption and transmission, especially, partial root-zone alternate drip irrigation repeatedly stimulates root rapid growth are important reasons for the increase root hydraulic conductivity. And alternate drip irrigation treatment’s plants can maintain the lower transpiration rate of per unit absorbing area. Thereby alternate partial rootzone irrigation plays an important role in improving water and fertilization use efficiency and regulating and controlling water consumption of the shoots. So we can conclude that alternate partial rootzone irrigation is conducive to improve the environment adaptability and the capacity of water-saving regulation and control and it shows wide application prospect not only in arid and semi-arid areas, but also in the saline area.更多还原