Stomatal density was recorded on every leaf of plants sampled from six varieties of grain sorghum, Sorghum bicolor (L.) Moench, and their 15 F1 hybrids. The plants were grown in the field at two locations in Kansas. Stomatal density on abaxial leaf surfaces was highest at the basal portion of the leaves. Heterosis was not observed when stomatal densities of parents and hybrids were compared. Among the 15 uppermost leaves, the second leaf from top had the highest density, and leaf no. 15 had the lowest. Stomatal density was higher on abaxial surfaces than on adaxial sides. Heritability estimate for stomatal density was high. That high befitability and little heterosis were observed for stomatal density supports the general principle that traits showing little or no heterosis tend to have high heritabillties. Total stomatal number per plant was higher in hybrids than in parents; the difference was attributable to more leaf‐blade area. Stomata on abaxial surfaces were longerthan those on adaxial surfaces; hybrids tended to have longer stomata than did parents. Grain yield per unit leaf area and per 106 stomates showed a similar trend: the performance of progeny resembled that of their parents. However, neither leaf area nor total stomatal number was significantly correlated with grain yield. Stomatal density was negatively correlated with grain yield and with stomatal length; total stomatal number was positively correlated with total leaf blade area.

ORGHUMS are a typical warm-season crop. Planting them in soil at low temperatures is deleterious to rapid establishment and vigorous seedling growth. Perhaps considerable variation in low temperature tolerance exists among currently available genotypes, but little information is available on this. Most sorghums originated in tropical areas near the equator (5), but Vavilov (5) places the origin of kaoliang in the Chinese center of crop origin. This center includes the mountainous regions of central and western China and their adjacent lowlands. Most kaoliangs are 'tall and have dry, woody, slender stalks. In general, they are sparsely leaved (3). Because of their northerly origin, it is reasonable that the kaoliangs might germinate and grow at lower temperatures than present-day grain sorghums grown in the United States (2). No critical data are available this question, however, and only limited information is available on temperature-germination responses in sorghums. Martin et al. (4) germinated four types of sor

Iron‐efficient and Fe‐inefficient sorghum [Sorghum bicolor (L.) Moench.] inbred lines and their F1 hybrid differed in response to Fe deficiency. These lines were used in growth chamber studies with a soil and with several liquid‐nutrient media to determine Fe‐use efficiency. An Fe‐deficient Colby silt loam soil (5.2 ppm DTPA extractable Fe) with 22.4 kg Fe/ha and without added Fe was used for a potted‐soil, growth study. In the remaining studies seedlings were grown in Hoagland nutrient solution to induce Fe deficiency, to determine effects of P levels and Fe sources, and to measure root reduction potential. The respective solutions used were: (i) 0.2‐strength solution with no Fe; 2.0 μM Fe and 3.0 mg CaCO3/ liter; 2.0 μM Fe and 5.0 mM P; 2.0 M Fe and 2.5, 25.0, and 10.0 μM Cu, Mn, and Zn, respectively; (ii) 0.5‐strength solution with 10.0 μM Fe at O, 0.5, 1.0, 2.5, and 5.0 mM levels of P; (iii) 0.5‐strength solution with 10.0 μM ferric and ferrous Fe; (iv) 0.2‐strength solution containing 2.0 μM Fe with the last 24 hours' growth in a ferrichloride‐ferricyanide solution. Plants from all studies were separated to roots and shoots, wet‐ash digested, and assayed for Fe, Cu, Mn, Zn, Ca, and Mg by atomic absorption spectrophotometry. Phosphorus was determined by the vanadomolybdophosphoric method. The Fe‐efficient inbred usually maintained lower P concentrations in shoots and commonly in roots under Fedeficient conditions. Antagonism from other nutrients except P was not involved consistently in differential response of Fe‐efficient and Fe‐inefficient lines. Root reduction potential for ferrichloride‐ferricyanide was lower for sorghum than for other crops, but did not differ between inbred lines. Shoot and root growth was always greater with ferrous than with ferric Fe. Efficiency of Fe use by sorghum apparently was not inherited by the hybrid. Iron efficiency in sorghum probably can be improved by accumulating genes that increase uptake of Fe, or by decreasing interference of P in utilization of Fe.

Genotypic and phenotypic correlations among 12 characters were estimated in segregating populations and in pure lines of grain sorghum (Sorghum bicolor Moench). Grain yield was positively and significantly correlated with head weight, kernel number, half bloom date, and leaf number, but negatively correlated with germination percentage and protein percentage. The inverse relationships between kernel weight and kernel number, and between kernel weight and head number per plant may arise from developmentally induced relationships or be genetically dependent. Head weight and half bloom date are considered best indicators for yield, while germination percentage may be of value as an indicator for protein content. Magnitudes of the estimates of expected progress in improving yield by selecting for characters other than yield appear to be greater than those for protein, indicating that direct selection for protein may be more effective in improving protein content.

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