Spray application factors and plant growth regulator performance: II. Foliar uptake of gibberellic acid and 2,4-D

Effects of droplet size and carrier volume on foliar uptake and translocati on of gibberellic acid (GA(3)) and 2,4-D were investigated. Simulated spray droplets were applied to primary leaves of 10-day-old Phaseolus vulgaris ( cv Nerina) in droplet sizes and carrier volumes ranging from 0.5 to 10 mu l and 10 to 200 mu l per leaf, respectively. Doses of GA(3) (2 mu g per leaf ) and 2,4-D (100 mu g per leaf) were held constant. Total uptake of GA(3) a pproached a penetration equilibrium within 24 H after application, but upta ke of 2, I-D continued to increase. Decreasing droplet size and/or increasi ng carrier volume increased GA(3) and 2,4-D uptake. Translocation to stem and roots was positively related to total uptake. a p ositive linear relationship between the logarithm of the total droplet/leaf surface interface area and 2, I-D uptake or translocation was found, but f or GA(3) this relationship was quadratic. Potential mechanisms of the effec ts of spray application factors on foliar uptake are discussed. (C) 1999 So ciety of Chemical Industry.