Breeding for drought resistance has been limited by the lack of a simple method of screening. Observations in the field cannot be made regularly, nor can the condition be repeated. A laboratory method of testing for drought resistance was needed. To investigate techniques, 10 cultivars of sorghum, Sorghum bicolor (L.) Moench, were planted in washed sand in plastic plots in a growth chamber. Five plants in each pot were fed a nutrient solution for 3 weeks. When they were harvested, wet root weight, root length, root volume, and root/shoot ratio were determined. The purpose of this study was to evaluate the root characteristics among 10 sorghum cultivars known to vary for drought resistance. Significant varietal differences for all characters were found. In general the most drought‐resistant cultivars had heavier root weight, greater root volume, and higher root/shoot ratios. This technique shows promise for identifying drought‐resistant lines, but it involved a considerable amount of time and labor. Root weight would probably be the most indicative and easiest characteristic to determine.

Three varieties of Sorghum bicolor (L.) Moench, (i.e., 'Early Hegari,' '80-Day 2Vlilo,' and 'Wheatland') were grown in controlled environment chambers and subjected to all combinations of 10-, 12-, and 14-hour photoperiods, 27 and 32 C day temperatures, and 16 and 21 C night temperatures. Days to floral initiation were determined for each variety under each treatment combination. In addition, days to anthesis and days in the floral period (from initiation to anthesis) were determined for the treatment combinations involving 21 C night temperatures. Ten-hour days hastened floral initiation and anthesis of each variety at all temperature combinations. ~'ourteenhour days delayed development, but with some temperature regimes the delay was not significant, compared to the shorter days. The rate of development for the varieties under 12-hour days was highly dependent upon day and night temperatures, since floral initiation ranged from as early as that obtained with 10-hour days to later than that obtained with 14-hour days. The response to day temperature during the floral period was small, but statistically significant. The time to anthesis followed a pattern similar to that for the time to floral initiation.

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