Penetration of foliar-applied chemicals can be influenced by a number of environmental conditions including: light, temperature, and humidity. These change during the day. 14C-benzyladenine (BA) was applied to the upper or lower surface of McIntosh apple leaves from 6:0 0 to 21:OO hours at 3 hour intervals. The amount of BA entering a leaf over a 24-hour period was not influenced by the time of application. Temperature was correlated with BA retention in the wax layer (correlation coefficients, r=0.06 4 and r=0.70 for the upper and lower surfaces, respectively) and with penetration through the upper surface (r=0.58). BA penetration into the leaf was not correlated with light intensity, relative humidity, or time of droplet drying.
Z. Y. Mao and D. W. Greene
Z.Y. Mao and Lyle E. Craker
Mulch, light level, and nitrogen fertilization were tested for their effects on productivity of horehound (Marrubium vulgaris L.). Yield of this plant increased under mulched conditions and with the addition of nitrogen fertilizer. Yield decreased with reduced light levels. Productivity of individual plants correlated with the number of branches per plant, leaf size, and leaf chlorophyll content. The number of branches per plant decreased with increased shading, but increased with increased nitrogen fertilization. The influence of mulch and shading on productivity could be due to the changes in soil temperature and in soil water potentials. Full-sun, high nitrogen, and mulch are suggested for optimum field production of horehound.