Effect of Drought and Nitrogen Availability on Osmotic Adjustment of Five Pearl Millet Cultivars in the Vegetative Growth Stage

Growth of pearl millet (Pennisetum glaucum (L.) R. Br.) is affected in areas with limited and erratic rainfall, often combined with nitrogen deficiency. Therefore, effects of severe drought and nitrogen availability on mechanisms of dehydration avoidance were investigated. Five pearl millet genotypes were cultivated in soil differing in nitrogen availability, low (N1), medium (N2) or high (N3) in a climate chamber. Thirty‐five days after sowing, the plants were exposed to drought for 12 days. Drought decreased leaf area and stomatal conductance strongly and caused leaf rolling. In the youngest fully expanded leaves, drought led to an osmotic adjustment from around ?0.5 to ?0.9 MPa, in N1 and N2 substantially achieved by potassium accumulation. Nitrate contributed to the osmotic adjustment in N2 and N3, proline only slightly, increasingly from N1 to N2, whereas the sum of glucose, fructose and sucrose did not play a role. The dehydration independent osmotic force for water uptake (osmotic potential at full turgor) was under drought strongest at N2 and in the landrace Dembi Yellow stronger than in the cultivars Ashana and Ugandi. This contributed to the higher relative water content (RWC) of ‘Dembi Yellow’, whereas due to other factors nitrogen had no effect on the RWC.     

黄淮海棉区棉麦两熟光能流与物质流研究 Ⅲ 麦棉共生期复合群体作物层温度分布与总积温

田间试验于１９９４／１９９５、１９９５／１９９６年采用满播小麦、一熟棉花和麦棉两熟不同配置方式４种处理研究了共生期麦棉复合群体作物层温度分布和总积温。结果表明，不同熟制、麦棉复合群体不同配置方式作物层温度垂直和水平方向廓线不同。与一熟棉花相比，共生期５２ｄ不同群体近地面作物层日平均温度２ａ显著低，依次是：满播小麦低７．２和４．６℃ｄ－１、３—１式麦带低５．６和４．１℃ｄ－１、４—２式麦带低５．５和３．４℃ｄ－１、３—１式棉带低２．９和２．９℃ｄ－１，４—２式棉带南行低２．８和２．４℃ｄ－１、４—２式棉带北行低２．６和１．６℃ｄ－１；共生期５２ｄ近地面作物层≥１５℃积温亏缺顺序是：满播小麦群体（－３７２．９和－２４１．２℃·ｄ）＞３—１式配置（－２３１．５和－１８４．６℃·ｄ）＞４—２式配置（－１８９．２和－１２８．７℃·ｄ）。不同复合群体温度日较差大小的顺序是：一熟地（２０．６℃ｄ－１）＞４—２式北行（１９．６℃ｄ－１）＞４—２式南行（１９．１℃ｄ－１）＞３—１式（１７．９℃ｄ－１）。共生期间温度日较差达到２０℃，有利于棉花培育早壮苗，唯４－２式棉带北行棉花趋于一熟棉花。本研究揭示出麦棉复合群体的低热量胁迫