Cellular response of two turfgrass cultivars to selected herbicides

Root meristem and root and foliage growth responses of Penncross' creeping bentgrass (Agrostis palustris Huds.) and Tifgreen' bermudagrass [Cynodon dactylon (L.) Pers. x Cynodon transvaelensis Burtt-Davy] to preemergence herbicides in solution culture were observed. The ability of the test species to recover following herbicide exposure was also evaluated.

Calcium arsenate [Ca₃(A₅O₄)₂] resulted in no significant shoot or root weight reductions of 'Penncross' bentgrass. Root meristem cells appeared similar to untreated plants. Chlorsulfuron [2-chloro-N-[[(4-methoxy-6-methyl-1,3,5- triazin-2-yl)amino]carbonyl)benzenesulfonamide] and fenarimol [α-(2-chlorophenyl)α-(4-chlorophenyl-5- pyrimidinemethanol) treatments resulted in considerable reductions of bentgrass shoot and root weights. Chlorsulfuron showed little effect in apical root cells but abnormally large numbers of root initials occurred in the sub-apical root region. Fenarimol exhibited little effect in both apical and sub-apical root cells. Pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] resulted in severe reductions of shoot and root weights of bentgrass. Extensive cell malformations and lateral root proliferations occurred in both the apical and sub-apical root region. Oryzalin [4-(dipropylamino)-3,5-dinitrobenzenesulfonamide) and sulfometuron [2-[[[[(4,6- dimethyl-2-pyrimidinyl)amino] carbonyl)amino]sulfonyl]- benzoic acid) resulted in very severe shoot and root weight reductions with massive damage in root meristem cells which eventually killed all plants.

Fenarimol and pendimethalin treatments resulted in only slight but significantly reduced shoot and root weights of bermudagrass. Apical root tips of fenarimol treatments appeared similar to untreated bermudagrass but a few abnormal lateral root proliferations were present in the sub-apical region. Pendimethalin resulted in greatly enlarged and malformed root meristems. Calcium arsenate and chlorsulfuron caused medium reductions in shoot and root weights of bermudagrass and cells in root meristems appeared similar to untreated plants. For the first 2 weeks following treatments with oryzalin and sulfometuron, bermudagrass shoots and roots grew rapidly, then a severe decline in overall growth occurred during the third week, followed by death of all plants between 4 and 8 weeks.