GROWTH AND PHOTOSYNTHETIC CHARACTERISTICS OF 2 BIOTYPES OF THE WEED BLACK-GRASS (ALOPECURUS-MYOSUROIDES HUDS) RESISTANT AND SUSCEPTIBLE TO THE HERBICIDE CHLOROTOLURON
Cr. Sharples et al., GROWTH AND PHOTOSYNTHETIC CHARACTERISTICS OF 2 BIOTYPES OF THE WEED BLACK-GRASS (ALOPECURUS-MYOSUROIDES HUDS) RESISTANT AND SUSCEPTIBLE TO THE HERBICIDE CHLOROTOLURON, Annals of botany, 79(4), 1997, pp. 455-461
Response of two biotypes of black-grass (Alopecurus myosuroides Huds.)
to the herbicide, chlorotoluron, was characterized in glasshouse and
laboratory studies. ED50 values, defined as the amount (kg active ingr
edient ha(-1)) of chlorotoluron required to reduce fresh mass by 50% u
nder standard conditions, were determined for a resistant biotype (39.
3 kg a.i. ha(-1)) collected from Peldon, Essex, UK and a susceptible b
iotype (0.93 kg a.i. ha(-1)) obtained commercially, giving a resistanc
e factor of 42. The resistance factor was calculated as the ratio of E
D50 values and describes the increase in amount of herbicide needed to
reduce fresh mass by 50% in the resistant, compared to the susceptibl
e, biotype. Resistance was further characterized by measurements of wh
ole plant growth and photosynthesis. Relative growth rate, number of t
illers, leaf area and mean fresh mass were the same in untreated plant
s of both biotypes, and rates of photosynthesis at both high and low p
hoton flux were similar, with no difference in apparent quantum yield.
Photosynthesis by whole plants was studied over a 24h period followin
g chlorotoluron treatment. Resistant plants showed no reduction in pho
tosynthesis over this period, whereas photosynthesis by susceptible pl
ants ceased 10h after treatment and did not recover. (C) 1997 Annals o
f Botany Company.