INVESTIGADORES
ECHARTE Laura
artículos
Título:
Effect of Verticillium dahliae on Photosynthesis, Leaf Expansion and Senescence of Field-grown Sunflower
Autor/es:
V.O. SADRAS; F. QUIROZ; L. ECHARTE; A. ESCANDE; V.R. PEREYRA
Revista:
ANNALS OF BOTANY
Referencias:
Año: 2000 vol. 86 p. 1007 - 1015
ISSN:
0305-7364
Resumen:
On the basis of known sunflower (Helianthus annuus L.) responses to soil water deficit, it is proposed that the effect of
the fungus Verticillium dahliae Klebahn on plant leaf area precedes and is greater than its effect on leaf photosynthesis
and stomatal conductance. To test this hypothesis, we measured shoot and leaf area growth, leaf photosynthetic rate,
stomatal conductance and disease symptoms in a field experiment including hybrids of high (Sankol) and low
(Dekasol 3900) susceptibility to V. dahliae. Plants inoculated with V. dahliae and controls were compared. We also
investigated the effect of V. dahliae on key components of plant leaf area, leaf expansion and senescence, in inoculated
and control plants of Sankol and Toba, a hybrid of intermediate susceptibility to V. dahliae. Reduction in plant leaf
area caused by V. dahliae was first detected 31 d after inoculation (DAI), when visual symptoms of disease in
inoculated plants were slight (Sankol) or absent (Dekasol 3900). Reduction in leaf photosynthesis was ®rst observed
66 DAI; stomatal conductance and leaf dark respiration were both unaffected by V. dahliae during the whole
experiment. In comparison with controls, V. dahliae reduced seasonal duration of plant leaf area by 25% in Dekalb
3900 and by 55% in Sankol, whereas the average reduction in leaf photosynthetic rate was 9 %. In correspondence
with the reduction in leaf area duration, inoculation reduced shoot dry matter of mature Sankol by 50 %. In both
experiments, less leaf expansion accounted for most of the early reduction in plant leaf area; as the disease progressed,
increasing senescence also contributed to reduced plant leaf area. It is concluded that the response of sunflower to
V. dahliae resembled the response of the plant to soil water deficit: (1) plant leaf area, rather than leaf photosynthetic
rate, accounted for the reduction in growth in mass; and (2) reduced leaf expansion early in the season and faster leaf
senescence in older plants accounted for the decrease in plant leaf area.