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CHEMICAL CONTROL, PHYSIOLOGY, ANATOMY, AND GLYPHOSATE ABSORPTION-TRANSLOCATION IN FIELD BINDWEED UNDER WATER STRESS
Abstract
Control of field bindweed (Convolvulus arvensis L.) with glyphosate {N-(phosphonomethyl)glycine} alone and glyphosate in combination with growth regulators was studied under field conditions and the effect of soil moisture on physiological, morphological-anatomical, and ('14)C-glyphosate absorption translocation characteristics of field bindweed were studied under greenhouse and laboratory conditions. Discing at least 4 weeks before herbicide application resulted in better control of field bindweed (79%) than in non-disced plots (55%) when other weeds were present. Field bindweed control was generally over 81% and up to 100% at glyphosate rates as low as 0.8 kg/ha following a discing when soil moisture was good. Low soil moisture without tillage gave under 66% control at rates up to 3.4 kg/ha. Of two ecotypes, the most common to Nebraska was more tolerant to glyphosate than a narrow-leaved type. Field bindweed control was best (88 to 100%) with 2 years application of glyphosate. Combining glyphosate with growth regulators, dicamba (3,6-dichloro-o-anisic acid), 2,4-D {(2,4-dichloro-phenoxy)acetic acid}, chlorflurenol {a combination of IT3456 (methyl-1-2-chloro-9-hydroxyfluorene-9-carboxylate), IT3294 (methyl-9-hydroxyfluorene-9-carboxylate), and IT5733 (methyl-2,7-dichloro-9-hydroxyfluorene-9-carboxylate)}, and ethephon (2-chloroethyl phosphonic acid) showed little improvement in control unless glyphosate was used at rates less than 0.8 kg/ha. The most effective treatment time for a single treatment was in September during rapid vegetative growth compared to October, or fruiting stage. Field bindweed control went from 21% with glyphosate alone at 0.6 kg/ha to over 88% when 2,4-D (0.6 or 0.1 kg/ha), dicamba (0.1 or 0.6 kg/ha), or ethephon (0.6 kg/ha) were added to glyphosate. Laboratory plants were grown from root segments for 65 days (young plants) and 100 days (mature plants). Water potential and leaf conductance were measured on young and mature plants which were kept under high (field capacity), medium (1/2 field capacity), and low (1/3 field capacity) soil moisture for 15 and 35 days, respectively. An overall reduction of the vegetative organs occurred in plants under moisture stress in the greenhouse. Water potential measurements showed that mature plants adapted to low soil moisture. Plants under medium soil moisture conditions and younger plants which were stressed only for 15 days maintained lower leaf water potentials (down to -19 bars). Leaf conductance per unit area was highest in plants under low soil moisture after adaptation and lowest in plants under medium soil moisture conditions. Low soil moisture caused an increase in cuticle and leaf thickness, more compact mesophyll cells and increased epicuticular wax deposition. Correlation coefficients were determined between physiological characteristics and morphological-anatomical characteristics and were more predictable in plants not adapted to stress (young plants) compared to those that adapted more to stress (mature plants). ('14)C-glyphosate was applied to exporting leaves of the young and mature plants and harvested 72 h later. About 20 (+OR-) 5% of recovered herbicide was taken up by the plants and from this amount, 45 (+OR-) 10% was translocated out of the treated leaf and accumulated in growing leaves and roots. Slightly more (6 (+OR-) 3%) herbicide was absorbed in plants under no stress than in plants under medium or low moisture stress. In young plants four to eight times more radioactivity accumulated in roots than in foliage (excluding treated leaf). Similar quantities of radioactivity accumulated in foliage and roots of mature plants. Such translocation may be a major factor in susceptability of young plants to glyphosate. Absorption and translocation were not affected enough by water stress to be a major factor in reduced glyphosate control of field bindweed under stress.
Subject Area
Agriculture
Recommended Citation
RASHED-MOHASSEL, MOHAMMAD-HASSAN, "CHEMICAL CONTROL, PHYSIOLOGY, ANATOMY, AND GLYPHOSATE ABSORPTION-TRANSLOCATION IN FIELD BINDWEED UNDER WATER STRESS" (1981). ETD collection for University of Nebraska-Lincoln. AAI8201039.
https://digitalcommons.unl.edu/dissertations/AAI8201039