Deep Root Water Uptake Ability and Water Use Efficiency of Pearl Millet in Comparison to Other Millet Species

Abstract

Pearl millet is better adapted to hot and semi-arid conditions than most other major cereals. The objective of this study was to compare the deep water uptake ability and water use efficiency (WUE) of pearl millet among millet species. First, the WUE of six millet species was evaluated in pots under waterlogging, well-watered (control), and drought conditions. Secondly, the water uptake from deep soil layers by pearl millet and barnyard millet, which showed the highest drought and waterlogging tolerance, respectively, was compared in long tubes which consisted of three parts (two loose soil layers separated by a hardpan and a Vaseline layer). Soil moisture was adjusted to well-watered and drought conditions in the upper (topsoil) layer, while the lower (deep) layer was always kept wet. WUE was significantly reduced in all millet species by waterlogging but not by drought. The ratio of WUE to the control condition indicated that pearl millet had the highest and lowest resistances to drought and waterlogging conditions, respectively, while barnyard millet was the most stable under both conditions. The deuterium concentration in xylem sap water, relative water uptake from deep soil layers, and water uptake efficiency of deep roots were significantly increased in barnyard millet but not in pearl millet by drought in topsoil layers. In conclusion, the drought resistance of pearl millet is explained by higher WUE but not by increased water uptake efficiency in deep soil layers as compared to barnyard millet, another drought-resistant millet species.     

Pearl Millet Developed Deep Roots and Changed Water Sources by Competition with Intercropped Cowpea in the Semiarid Environment of Northern Namibia

abstract

The practice of intercropping pearl millet with cowpea is widespread among subsistence farmers in northern Namibia. In this region, the scarce and erratic rainfall may enhance competition for the limited soil water between intercropped plants. Trials were conducted on a field of the University of Namibia (on-station) and on a farmer’s field (off-station) to determine the effects of competition between pearl millet and cowpea on the water sources and plant growth of each crop. The deuterium analysis showed that pearl millet, intercropped with cowpea, significantly increased its dependence on the recently supplied labeled irrigation water. Intercropped cowpea also showed an increased trend of the dependence but it was not statistically significant. At the university field, intercropped pearl millet showed higher dependence on the irrigation water than monocropped pearl millet. At the farmer’s field, the dependence of intercropped pearl millet on the irrigation water was low in the pearl millet-dominant zone. In contrast, the dependence on the irrigation water was high in the cowpea-dominant zone, indicating that the dependence on the irrigation water changes according to the size of the pearl millet canopy. The water sources of cowpea did not show a significant difference at either pearl millet-dominant or cowpea-dominant zone, indicating a stable water uptake trend under competitive conditions. Competition with cowpea significantly increased the root-weight density of intercropped pearl millet in the deep soil layers, but decreased that in the shallow layers. The root-weight density of intercropped cowpea, however, was reduced in most of the soil layers. In conclusion, cowpea has a higher ability to acquire existing soil water, forcing pearl millet to develop deep roots and shift to the surface irrigation water.     

Water Acquisition From The Seasonal Wetland and Root Development of Pearl Millet Intercropped With Cowpea in A Flooding Ecosystem of Northern Namibia

Abstract

Seasonal Wetlands, Locally Called Oshanas, Are Characteristic of The Densely Populated Northern Namibia, A Desert Country in Southwest Africa. The Formation of Seasonal Wetlands, Which Will Sustain The Water Balance of A Semiarid Environment, Was Quite Unstable Depending Entirely On The Variable Rainfall in The Upper Catchments of Angola. The Objective of The Present Study Was To Evaluate The Use of Seasonal Wetland Water By Pearl Millet, The Local Staple Food Crop intercropped With Cowpea, To Discuss The Water Competition Pattern of intercropped Species. Root System Development of The intercropped Species Was Also Evaluated Together With The Water Source Analysis. For This Purpose, Field Experiments Using Pearl Millet intercropped With Cowpea in The Seasonal Wetland in Namibia University (Exp. 1) and Monocropped Pearl Millet in The Local Farmers Field (Exp. 2) Were Conducted in Northern Namibia. Both Pearl Millet and Cowpea Developed Deeper Root Systems As The Distance From The Seasonal Wetland Water increased. At Flowering Time, The δD Value of intercropped Cowpea Was Similar To That of Wetland Water, While That in Pearl Millet Was Much Lower Than Those of Both The Wetland Water and Groundwater. This indicated That intercropped Pearl Millet Did Not Have Full Access To The Wetland Water When There Was Competition With Cowpea For Water Derived From Various Water Sources. Under Such Circumstances, intercropped Pearl Millet Probably Relies More On The Rainfall Water, Which Is Just Sufficient To Sustain Its Growth in A Semiarid Environment. By Contrast, intercropped Cowpea Wins in The Competition With Pearl Millet and Can Acquire Water From The Existing Stored Wetland Water.     

Genotypic Variation in Biomass Production at the Early Vegetative Stage among Rice Cultivars Subjected to Deficient Soil Moisture Regimes and Its Association with Water Uptake Capacity

References

Genetic improvement in water uptake ability and/or water use efficiency (WUE) of rice cultivars is one option to enhance productivity under water-limited conditions. We examined the genotypic variation in biomass production among 70 rice cultivars (69 cultivars of NIAS global rice core collection and Azucena) under different soil moisture conditions, and to identify whether water uptake ability or WUE is responsible for the variation, if any. Two-week-old seedlings were transplanted into pots and grown for three weeks in an environmentally-regulated growth chamber under three soil moisture regimes: flooded (?0.02 MPa soil water potential) and two unflooded (?0.10 and ?0.52 MPa) conditions. Substantial genotypic variations in total dry weight (TDW) were observed under all three regimes. Among all the cultivars tested, TDW was significantly correlated with water uptake ability, but not with WUE. However, several cultivars exhibited comparably higher WUE while showing superior biomass production under the ?0.52 MPa regime. The amount of water uptake was significantly correlated with root dry weight among cultivars regardless of moisture regimes, while substantial genotypic difference in the amount of water uptake per unit root dry weight was observed. These results indicate that a marked genotypic difference exists in biomass production at the early vegetative growth under water-deficient conditions, and that this difference appears to be ascribed primarily to greater water uptake capacity, and additionally to higher WUE in drought-tolerant cultivars.     

Hydraulic Conductivity and Aquaporins of Cortical Cells in Gravitropically Bending Roots of Pisum sativum L.

Abstract

We examined the differential elongation of gravitropically bending roots of Pisum sativum L. in terms of cell enlargement and water uptake by cells in the growing tissue. Hydraulic conductivity between the elongating and mature tissues (Lp) was estimated from the equation G = A × Lp × Δψ, where G is the water-uptake rate, A is the surface area of a single cell and Δψ is the driving force. The rate of entry of water into a cell was estimated from the rate of increase in the volumes of cells in the outer cortex, which were calculated from longitudinal sections at given times. Gravitropic bending occurred 1 h after the application of gravi-stimulation and the curvature increased rapidly for the next 3 h. The biggest difference in the partial elongation rate between opposite sides of a root was found in the region 3 to 4 mm from the root tip at the start of stimulation. Cell enlargement rate was 2.8 to 3.8 times greater on the upper side of the root than on the lower side. The water potential and the osmotic potential, in both the elongating and mature tissues, were the same on both sides of the root. Therefore, there was no difference in the driving force for water flow. Hydraulic conductivity was 2.3 to 4.2 times greater on the upper side of the root than on the lower side. There was no difference between the upper and lower sides of the root in the amounts of 19-kD and 24-kD proteins in membrane fractions, which we assumed to be aquaporins (putative aquaporins), as estimated with two preparations of polyclonal antibodies. The differential elongation that occurred during root gravitropism was caused by a difference in Lp. However, the difference in Lp did not appear to be regulated by the concentration in cell membranes of the putative aquaporins.     

玉米主要抗旱性状的配合力及遗传参数分析Ⅲ.生育时期

按Griffing双列杂交(Ⅳ)方法,分析了8个玉米自交系的播种至散粉期日数、播种至吐丝期日数和散粉至吐丝间隔在雨养地和水分胁迫下的GCA、SCA及遗传变量.结果表明:三者均以加性基因效应为主,选择时GCA较为重要;水分胁迫对生育时期的影响较大,对其遗传改进和选择应在正常条件下进行。     

百色干热河谷地区降雨氢氧稳定同位素特征及芒果树水分来源研究

百色市右江河谷是我国著名的干热河谷之一,干旱是该地区最严重的气象灾害。芒果是该地区地理标志农产品,但其水分利用策略尚不清楚。本文基于氢氧稳定同位素示踪技术研究该地区降雨同位素特征及影响因素,利用多元线性混合模型方法量化不同来源水分对芒果树根系吸水的贡献比例,揭示芒果树生育期内水分利用策略。结果表明：（1）研究区氢氧稳定同位素具有明显的季节变化,δ值和氘盈余（d）具有旱季富集、雨季贫化的规律,建立了研究区的大气降水线方程：δD=8.2587δ18O+12.308,δD和δ18O值有极显著相关性（r=0.9968, n=35, P<0.001）;(2)季风气候影响下大气降水稳定同位素值具有显著的降雨量效应和反温度效应（P<0.05）;(3)在芒果花期、幼果期、果实膨大期和成熟期,土壤水氢氧稳定同位素总体上随土壤深度的增加而变贫;在花期和幼果期,芒果树对各层次土壤水分及地下水利用比例较为均匀,果树膨大期和成熟期则主要利用深层次土壤水及地下水,表明该地区芒果树主要以深层次土壤水及地下水为水源,说明芒果树更接近于保守型水分利用策略。降雨氢氧稳定同位素特征反映了该地区干热的气候特征,芒...