苜蓿、玉米根系提水作用测定的影响因素——植物根系提水作用机理研究I

通过一种上干下湿的分根装置,应用中子水分仪在大田条件下研究了苜蓿和玉米根系提水作用测定中几种相关因素的作用和影响,提出了总提水作用的概念和测算模式.结果显示,夜间9 h(20∶00~5∶00)的表观根系提水量(Qm),一龄苜蓿为8.02 g,开花期的中单2号和豫玉22玉米分别为7.52 g和4.76 g.但其蒸腾失水量(Qt)平均分别为90.26 g4、6.94 g和48.07 g,供试土壤表面的自然蒸发量和上下土层之间隔水层的毛管升水量,苜蓿处理为6.60 g和6,58 g,玉米处理为5.20 g和6.66 g.分别占每株供试苜蓿表观根系提水量(Qm)的11.25倍、82.3%和82.1%,中单2号玉米的6.24倍、69.1%和88.6%,豫玉22玉米的10.1倍、109.2%和139.9%.表明被测植株的蒸腾速率、供试土壤表面水分的自然蒸发和隔水层的毛管作用对植物根系提水作用测定有着及其显著的影响.因此,植物总根系提水量QT应由实际提水量Qp与植株的蒸腾量Qt两部分构成,其中Qp为表观提水量Qm与上层土壤的蒸发量Qe之和再减去隔水层的毛管升水量Qc,即:QT=Qp+Qt=(Qm+Qe-Qc)+Qt.

Studies on mechanism on hydraulic lift in plant root system——Factors influencing on determining hydraulic lift in root system of alfalfa and maize

The factors influencing on determining the hydraulic lift(HL) in the root system of alfalfa and maize were studied with neutron probe in the field by a device with a drier topsoil(shallow soil layers) and a moist subsoil(deep soil layers),which allowed to grow their root system into two soil compartments.A new concept on total hydraulic lift and a mathematical model were developed.The results showed that during 9 h of over night the average amount of apparent HL(Qm) in 1-year-old alfalfa after being sown 5 mouths was 8.02 g,and the two maize cultivars of 'Zhongdan 2' and 'Yuyu 22' in flowering stage were 7.52 g and 4.76 g,respectively.But the average water loss weight transpirated(Qt)from the blades of 1year-old alfalfa was 90.26 g,the maize cultivar 'Zhongdan 2' and 'Yuyu 22' was 46.94 g and 48.07g,respectively.The average loss amount of water evaporated(Qe) from the surface of topsoil under growing alfalfa was 6.60 g and that under growing maize was 5.20 g.The amount of water lifted over night by the capillary penetration(Qc)through the water-obstructed layer between the topsoil and subsoil under growing alfalfa was 6.58 g and that under growing maize was 6.66 g.The rate of Qt,Qe and Qc with the apparent HL of 1-year-old alfalfa were 11.25 times,82.3 % and 82.1 %,the maize cultivar 'Zhongdan 2' were 6.24 times,69.1 % and 88.6 %,and the maize cultivar 'Yuyu 22' were 10.1 times,109.2 % and 139.9 % respectively.The results above indicated that Qt,Qe and Qc significantly influenced on determining the hydraulic lift(HL) of 1-year-old alfalfa,and the two maize cultivars.Therefore,the total amount(QT) in the plant root system should be composed with the actual amount of water lift(Qp) and Qt.Qp should be equal to the summation of Qm and Qe with the difference of Qc,that is:QT=Qp Qt=(Qm Qe-Qc) Qt.