【作者】 李霞；

【导师】 王国栋； 薛绪掌；

【作者基本信息】 西北农林科技大学 ， 生物物理学， 2009， 博士

【摘要】 本篇论文在日光温室内通过调控光照、大气湿度、温度、气流运动速度、土壤水分等环境因子,来研究植株蒸腾耗水。期望能找到最佳的环境条件,减少植株无效蒸腾,提高水分利用效率,从而为设施农业水资源的节约利用方面提供理论和实践依据。该文的主要研究结果如下:1、在茎热平衡技术测定植株茎流的原理基础上,结合温室内气象数据采集仪器,通过对小温室做密闭、遮光处理,探讨番茄茎流的变化规律。结果表明,密闭温室处理后晴天番茄茎流变化趋势不变,但白天茎流明显减小,此时影响茎流的环境参数除光照外,温室内的大气温度、空气相对湿度等都不能忽略。白天人为改变光照,茎流随光照的降低而逐渐减小,变化规律与光照强度的变化规律相似,但茎流变化曲线稍稍滞后于光照的变化曲线;在时间上有一个延迟。当白天遮光变温室为“黑暗”状态时,茎流缓慢减小,但此时茎流远远大于夜晚茎流,而且白天温室内“黑暗”状态处理的不同时间段茎流减小的快慢是不一样的。2、在温室盆栽条件下,以京苋四号苋菜作为试验材料,研究了不同覆盖度处理下盆栽小环境温湿度的变化以及植株蒸腾耗水规律。综合分析结果表明:植株生长点的温湿度随覆盖度的增大而增加,蒸腾速率和昼夜蒸腾量随覆盖度的增大而减小。文中通过逐步回归分析给出了不同覆盖处理下盆栽苋菜的蒸腾速率、白天蒸腾量与气象因子的相关关系。不同覆盖处理对温室盆栽苋菜的根冠比、叶绿素相对含量、蒸腾耗水量、干物质积累量以及水分利用效率均有极显著的影响,除了水分利用效率随覆盖度的增加而增大,其它均随覆盖度的增加而减小。15/16圆覆盖处理水分利用效率是对照处理1.45倍;15/16圆覆盖、3/4圆覆盖、1/2圆覆盖、无圆覆盖处理的蒸腾耗水量分别为对照处理的32.65%、54.64%、63.36%和69.98%。可见密封一部分空间,抑制了植株蒸腾耗水,同时也提高了水分利用效率。3、风的大小是影响植株生长、蒸腾的一个重要因素。而温室内风速几乎为零,因此通过温室盆栽试验,采用基质栽培,设置了两种蔬菜(甜椒和苋菜)的不同风速试验,来研究风对植株生长及蒸腾耗水的影响。研究结果表明,盆栽甜椒的日蒸腾量,苗期差别不大,整体是随风速增加而增大;随着植株的生长,不同风速盆栽甜椒的日蒸腾耗水量的差距拉大,0.8m·s-1的日蒸腾量超过1.2m·s-1的,此时盆栽甜椒的日蒸腾量表现为: T2>T3>T1>CK;试验后期,对照盆栽的日蒸腾量超过0.4m·s-1的,盆栽甜椒日蒸腾量表现为:T2>T3>CK>T1。而根据盆栽苋菜的蒸腾速率和日蒸腾量曲线看出,不同风速处理对盆栽苋菜蒸腾的影响不大,蒸腾速率及日蒸腾量受不同风速影响的表现相同,整体看来,以1.0m·s-1风速处理盆栽的最大,0.4m·s-1风速处理和对照盆栽的次之,最大风速处理2.0m·s-1盆栽的蒸腾速率及日蒸腾量最小。由以上结果可知,两个试验所设置的风速处理对两种蔬菜蒸腾的影响存在差异。原因是多方面的,作物自身的遗传差异;两个试验的季节不同,温湿度环境因子的差异;风速处理不同,特别是最大风速设置不一样,还有送风时间不同;这些都是造成两次试验结果存在出入的可能原因。文中还通过多元线性逐步回归分析给出蒸腾与环境因子的相关关系。试验中最适宜盆栽甜椒、苋菜生长及蒸腾的风速分别为0.8m·s-1和1.0m·s-1。盆栽甜椒在最大风速(1.2m·s-1)处理下产量最低,作物水分生产率最低;而盆栽苋菜在最大风速(2.0m·s-1)处理下,干物质重最低,水分利用效率最低;可见,风速偏高增加了植株的“无效”蒸腾,同时也降低了作物产量。4、采用负水头供水控水盆栽装置,设置四个供水吸力,对盆栽番茄蒸腾和鲜物质积累动态进行了研究。结果表明:负水头盆栽装置实现了对基质含水量的精确控制,10hPa、30hPa、50hPa、70hPa吸力下盆栽基质含水量分别在88%、76%、63%和57%左右。番茄日蒸腾量因基质水分的不同而不同,试验初期是30hPa吸力的日蒸腾量最大,10hPa的次之,50hPa的最小;到了试验中后期,10hPa吸力的日蒸腾量超过30hPa的位居第一。通过逐步回归分析给出不同吸力下盆栽番茄的日蒸腾量与气象因子的相关关系。从番茄的鲜物质积累曲线看出,基质水分处理引起盆栽番茄物质积累的差异非常显著,30hPa吸力下的鲜物质积累量最大,10hPa和50hPa的次之,70hPa的最小。基质水分处理对温室盆栽番茄叶片的蒸腾速率和气孔导度有极显著影响,对光合速率有显著影响,而对叶绿素含量和胞间CO2的浓度影响不大;同时对盆栽番茄的产量、总蒸腾耗水量和作物水分生产率均有极显著影响。10hPa供水吸力下的总蒸腾耗水量最大,产量最低,可见基质含水量过高,增加了植株的“无效”蒸腾,降低了作物水分利用效率。5、对盆栽做双层全覆盖处理,调控密闭盆栽小环境内的温湿度,降温除湿的同时想办法把蒸腾水回收利用到盆栽中,这将在设施农业水资源节约利用方面迈出开创性的一步。本章利用温差进行热交换原理,初步探索了降温除湿回收利用蒸腾水的试验效果。首先,利用“水-气温差”对密闭盆栽进行降温回收蒸腾水同时除湿。试验初期,降温除湿效果显著,正午12:30左右,相比密闭对照盆栽,温度降低3℃左右,相对湿度下降7%;其它时间降温除湿效果虽不及正午时分,但白天平均降温2.4℃,相对湿度平均下降5%。但试验持续几天之后,回收的蒸腾水都聚集在U型管中,最终充满U型管底部,气流不能循环,试验最终起不到降温除湿的目的。之后,利用“地-气温差”进行热交换、利用气泵使水汽循环,来对密闭盆栽进行降温除湿回收利用蒸腾水。试验过程中,夜晚的降温除湿效果不明显。夜晚密闭对照盆栽、地-气热交换处理盆栽小环境内的气温与温室内的气温基本一致;相对于密闭对照盆栽,相对湿度平均下降6.2%;夜晚不开气泵时,地-气热交换处理盆栽内相对湿度比对照盆栽低5.6%左右。白天在气泵运行过程中,地-气热交换处理盆栽相对于密闭对照盆栽温度平均下降2.5℃左右;相对湿度平均下降10%左右。正午时分,降温除湿效果最为显著,相比密闭对照盆栽气温降5℃以上,与温室内的温差只有1.5℃左右;此时湿度下降15%左右。降温后凝结而成的水珠在高速气流的带动下又重新回收到盆栽中。更多还原

【Abstract】 This paper studied plant transpiration through regulating and controlling environmental factors in greenhouse. We expected to find optimum environment condition for decreasing "inefficient" transpiration and improving water use efficiency. These would provide a basis for water economized using of facilities agriculture. The main results are as following:1. On the basis of the stem heat balance principle to measure the plant transpiration, with the instruments to collect meteorological data in greenhouse, we studied the variational rules of tomato sap flow under different environmental treatments through shading and obturating environment.The results showed the trend of tomato sunny sap flow was invariable in the obturated greenhouse,but sap flow was obviously diminished.Besides illuminance,temperature and humidity were necessary environmental parameters to affect tomato sap flow in greenhouse. Under the treatment of changing illuminance artificially in the daytime, sap flow was gradually diminished following the illuminance reduced, they had similar rules. But the sap flow curve was lagged to the illuminance curve, and had a time delay. When the greenhouse became dark in the daytime, sap flow was gradually diminished, but sap flow value was far bigger than sap flow value at night. When the greenhouse was in the dark in the different time section, the diminished speed of tomato sap flow was different.2. Through pot experiment, air temperature and humidity at growth point of amaranth, and transpiration consumption were studied under different surface coverage degrees in greenhouse. The results showed, the air temperature and humidity increased as the coverage degree rose. During day and night, transpiration decreased as coverage degree increased. Meanwhile, stepwise regression analyses revealed significant correlation between transpiration rate, daytime transpiration consumption and meteorological parameters under different surface coverage degrees. The effects of different surface coverages on root-top ratio, chlorophyll content, transpiration consumption, dry matter accumulation and water use efficiency of potted amaranth were extremely significant. Except water use efficiency increasing with the coverage degree enhanced, others diminished with the coverage degree increased. Water use efficiency of 15/16 circle coverage is 1.45 times of the comparison treatment; transpiration consumptions of 15/16 circle coverage, 3/4 circle coverage, 1/2 circle coverage and non-circle coverage treatment were 32.65%, 54.64%, 63.36% and 69.98% of the comparison treatment, respectively. Transpiration was bated and water use efficiency was enhanced at the same time passing sealing the part of space.3. Wind speed is a key factor to affect plant growth and transpiration. Setting different wind speed of two vegetable (sweet pepper and amaranth), we studied the effects of wind on vegetable transpiration and growth through pot experiment in greenhouse. The results showed, difference among day transpiration of sweet pepper seedlings under different wind speed was small, with day transpiration generally increasing as wind speed rose. As sweet pepper grew up, potted day transpiration disparities at different wind speed increased, day transpiration at 0.8m·s-1 exceeded its at 1.2m·s-1, now potted day transpiration showed by: T2> T3> T1> CK. In the late experiment period, CK’s exceeded its at 0.4m·s-1, presented as: T2> T3> CK> T1. But according to the curves of potted amaranth transpiration rate and day transpiration, the effects of wind on potted amaranth transpiration is not much, their patients are identical affected by different wind speed. In general, transpiration rate and daily transpiration at 1.0m·s-1 are maximum, followed by those of 0.4m·s-1 and 0.0m·s-1, and the least at 2.0m·s-1. By all above results, there are differences in the effects of wind speed treaments of two experiments on two vegetables transpiration. There are many reasons passing analysis, crop itself exists genetic differences; two experimental seasons were different, there were notable differences of temperature and humidity environment factors; Wind speed treatments diversity, especially maximal wind speed was different; and supplying wind time was various. These are all possible reasons to cause two experimental result differences. Stepwise regression analyses revealed significant correlation between transpiration and meteorological parameters under different wind speeds. The best wind speed for sweet pepper growth and transpiration in greenhouse was 0.8m·s-1, it was 1.0m·s-1 for amaranth. Potted sweet pepper yield and crop water productivity under the most high wind speed (1.2m·s-1) were minimum; likewise, potted amaranth dry matter weight and water use efficiency were minimum. It was obvious that excessive wind speed increased "inefficient" transpiration, and reduced crop yield.4. Setting water supply tension at 10hPa, 30hPa, 50hPa and 70hPa, we studied the effects of water supply tension on transpiration and fresh matter accumulation of potted tomato by using negative pressure pot device in greenhouse. The results showed that the negative pressure pot device can realize the accuracy control to substrate moisture content, the substrate moisture content of pot equipment are 88%, 76%, 63% and 57% respectively under water supply tension at 10hPa, 30hPa, 50hPa and 70hPa. Daily transpiration of potted tomato is different because of the different substrate moisture treatments. At the beginning, daily transpiration of potted tomato at 30hPa is maximum, the second is 10hPa, and the least is 50hPa. During Medium-late Stage of experiment, daily transpiration of potted tomato at 10hPa is the first. At the same time, stepwise regression analyses revealed significant correlation between daily transpiration and meteorological parameters under water supply tension. Based on the fresh matter accumulation curve of potted tomato, the differences among the fresh matter accumulation of potted tomato caused by substrate moisture treatments are very significant, its of the 30hPa tension is maximal, followed by 10hPa and 50hPa, it is minimum at 70hPa. The effects of water supply tension in greenhouse on transpiration rate and stomatal conductance of potted tomato are extremely significant, it is notable effect to photosynthetic rate, but the effects to chlorophyll content and intercellular CO2 are not significant. Meanwhile, the effects of water supply tension on yield, transpiration water consumption and crop water productivity are extremely significant. The transpiration water consumption at 10hPa water supply tension is maximal, its yield is minimum. Therefore, excessive substrate moisture content increased "inefficient" transpiration, and reduced crop water productivity.5. Setting double-coverage treatment to the pot, we may regulate temperature and humidity in the closed pot. Dehumidifying and cooling, at the same time trying to recycle transpiration water to the pot. we will stride inaugurated one-step in the economical utilization of facility agriculture water resources. According to the principle of temperature disparity for heat exchange on this chapter, we explored preliminarily experimental effect of dehumidification, cooling down and recycling transpiration water. Firstly, we made use of temperature difference between water and air to dehumidify, cool down and recycle transpiration water in small closed environment. During the experiment initial stage, the effect of dehumidifying and cooling was remarkable. Compared with the closed check pot, its temperature reduces 3℃or so and its relative humidity comes down 7% at 12:30; dehumidifying and cooling effect in other time is inferior to that at noon, but its temperature cools down averagely 2.4℃in the daytime, and its relative humidity reduces averagely 5%. But several days later, recycled transpiration water all aggregates in U-tube, ultimately full of the bottom of U-tube, it makes air flow can not complete circulation, the test was fail. Afterwards, based on soil-to-air temperature difference for heat exchange, by using air pump to recycle vapor, we designed device to dehumidify, cool down and recycle transpiration water in the closed pot microenvironment. During the experiment, dehumidifying and cooling effect is not obvious in night. Temperature is basically consistent between the closed check pot and the pot treated by soil-air heat exchange in night; compared with the closed check pot, its relative humidity decreases averagely 6.2%; in night without opening pump, relative humidity of the pot treated by soil-air heat exchange field- gas heat exchange handles is 5.6% lower than that of the check. In the daytime with pump operation, compared with the closed check pot, temperature goes down averagely 2.5℃and relative humidity reduces 10% or so. At noon, there is the most notable effect of dehumidifying and cooling, its temperature decreases 5℃relative to the check, the temperature difference is 1.5℃or so between in the treated pot microenvironment and in greenhouse; humidity reduces 15%. Condensed water for cooling recycles to the pot under the drive of high speed flow.更多还原