The comparative drought resistance of sorghums
1930
Martin, J.H.
Grain sorghums, because of their superior drought-resistance, largely replace corn in the Southwest where the average annual precipitation is less than 25 inches. Sorghum leaves have more stomata per unit of area and smaller stomata than corn leaves, sorghums in each case showing typical xerophytic characters. Sorghum leaves and stems have a waxy and cutinized epidermis which reduces evaporation. Sorghum plants are less leafy than corn plants and have more secondary roots. The osmotic concentration of leaf juices is lower and that of the stalk, crown, and root juices is higher in sorghums than in corn. Sorghum stalks have a lower moisture content than corn stalks. Sorghum has a lower transpiration ratio than corn under conditions of high evaporation. Sorghum leaves and stalks wilt and dry more slowly than those of corn. The slower drying permits sorghum plants to withstand drought longer than corn and they may subsequently recover when moisture becomes available. The waxy cuticle apparently is largely responsible for the slow drying of sorghums. It's believed that the sorghum stalk recovers from a dormancy induced by drought chiefly because it has not wilted beyond recovery. Sorghum plants can send up tillers and still produce a good crop if rains come after the main stalks have been killed by drought. Ear]y types of grain sorghum sometimes partly escape drought and produce some grain before the soil moisture becomes exhausted when kafir is a complete failure.
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