EFFECT OF PLANT MOISTURE STRESS AND APPLICATION SURFACE ON UPTAKE AND TRANSLOCATION OF TRICLOPYR WITH ORGANOSILICONE SURFACTANT IN RED MAPLE SEEDLINGS

This study investigated the effect of plant moisture stress and surface of application on the absorption, translocation, and ''rainfastness'' (short-term ability to retain herbicide) of organosilicone-adjuvated (adjuvant added) [C-14]triclopyr amine on greenhouse-grown, 4-month-old red maple (Acer rubrum L.) seedlings. Xylem water potentials were -1.6 and -0.9 MPa and leaf conductances were 0.07 and 0.13 cm . s(-1) for the stressed and control seedlings, respectively At 2 h, rainfastness was 13% less for stressed seedlings. Uptake increased with time, and by 72 h no effect of moisture stress treatment was apparent. Abaxial absorption into living leaf tissue was 57% greater at 72 h than was adaxial absorption, but application surface did not significantly affect translocation. Plant moisture stress did, however, reduce translocation of herbicide into the shoots and roots. Organosilicone surfactants may enhance long-term triclopyr uptake in water-stressed seedlings, but do not appear to facilitate translocation in stressed seedlings. Plant moisture status, therefore, should continue to be a concern when scheduling herbicide applications.