Better logic is needed for predicting genetic and environmental effects on canopy leaf expansion and stem extension. We measured leaf area and intemode lengths and dry masses for 19 strains of Zea mays L., with mature leaf numbers ranging from 10 to 27, at a uniform population density. Similar measurements were made on plants growing in four different plant densities for one of the cultivars (Pioneer 3344). The number of the ear nodes correlated well with total leaf number. In generál, area per ear-node leaf increased up to 20 total leaves, with considerable variability among strains having roughly the same total leaf number. Other generál relationships were found between total leaf number and (a) the nodal position of the leaf with maximum area, as well as (h) the two positions above and below the ear node for 1/2 maximum area, (c) intemode lengths, and (d) intemode dry masses. Such information can be ušed for developing better maize production management models, as well as better selection methods for increased productivity.
Soybean [Glycine mctx (L.) Merr. cv. Jack] was grown in the field in rain-prolected plots to study effects of drought and atmospheric CO2 enrichnient on leaf gas exchange. Midday depressions in leaf photosynthetic CO2 exchange rates were found in drought-sfressed plants and the diumal changes were inostly stoinatal- regulated, although accumulated drought stress eventually resulted in some non- stomatal limitations. However, seasonal changes in were mostly limited by non- stomatal factors. Water use efficiency was always higher for drought stiessed plants and depended on the severity of stress and associated stomatal or nonstoinatal limitations. At enriched atmospheric CO2 levels, stomatal limitations to Pyj under drought stress were less important than at ambient atmospheric CO2 levels. Morning and aftemoon leaf starch levels were enhanced in both irrigated and nonirrigated plants in enriched CO2. Aftemoon starch levels were higher in stiessed leaves than in non-stressed leaves at normál CO2 levels.