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.
A versatile and inexpensive systém with a hand scanner was developed and evaluated for measuring leaf area. A BASIC programme was created for processing the image fíles and calculating the area of scanned objects. The accuracy was better than 1 % of the reference area and it fell only when the area/perimeter ratio was less than 0.3 or when the measured object size was smaller than 0.1 cm^.