EFFECTS OF TEMPERATURE AND SUNLIGHT ON THE RATE OF ELONGATION OF STEMS OF MAIZE AND GLADIOLUS

Abstract

Measurements of the height of the main stems of maize and gladiolus plants were made at four-hour intervals starting at 4 a.m. The increases in elongation were analyzed statistically, together with mean temperature, hours of sunlight, and mean relative humidity.Partial correlation coefficients showed that there was a highly significant positive association between the rate of stem elongation (growth) and temperature, regardless of the time of day, the variations in temperature accounting for from 40 to 70% of the variability in growth rates. There was likewise a significant negative correlation between growth and sunlight, but sunlight was apparently effective only during the midday periods (8 a.m. to 4 p.m.). The depressing effect of sunlight on the growth of gladiolus was approximately four times as great as on maize. This depressing effect on maize was entirely removed by shading the plants with light white cotton.Variations in relative humidity were only slightly associated with growth rates. No significant effect was observed for any of the periods. It seems possible that these factors might be more important under conditions of deficiency in soil moisture.The approximate minimum temperature at which growth look place was 40° F.