New
Phytologist 115: 503-510 (July
1990)
Drought
acclimation and the morphology of mycorrhizal Rosa hybrida L. cv. 'Ferdy' is
independent of leaf elemental content
Janet C.
Henderson, Freed T. Davies Jr.
SUMMARY
Rosa
hybrida L. cv.
‘Ferdy’ is a low maintenance landscape plant which is considered drought
resistant. To determine the effects of endomycorrhizae on plant water relations
and growth, rooted cuttings of uniform size were established in containers
under moderately high P fertilization. Vesicular arbuscular
(VA) mycorrhiza inoculated and noninoculated plants were placed under three
water regimes: drought acclimated, non acclimated
and later exposed to drought, or non stressed.
Acclimated plants were conditioned by four 3-d
and three 4-d drought cycles. Non acclimated plants received water daily prior to a single
4 d drought cycles, and non stressed plants were watered daily throughout the study.
Under water deficits, non acclimated plants had
lower leaf water potentials (ΨL),
transpiration rates (E) and stomatal conductances (g), than acclimated or non stressed plants. Non acclimated
plants also had a greater leaf area, leaf number and shoot dry weight than
acclimated plants, yet had a comparable leaf area ratio (LAR) and root shoot ratio. Mycorrhizal plants had a higher E, than non mycorrhizal plants, even though non mycorrhizal plants were of comparable biomass (leaf area,
shoot and root dry weight and LAR). However, the root shoot ratio was greater with mycorrhizal plants which had
fewer leaves (due to abscission), and lower cuticle and epicuticular wax
weights than non mycorrhizal plants. There was no
affect of VA mycorrhiza on leaf osmotic potential (Ψn) stomatal density, leaf cell density, leaf area, or macronutrient
uptake. Acclimation of this low maintenance
landscape rose cultivar to water deficits and the mechanism of drought
avoidance via leaf abscission, were as beneficial to drought resistance as was
mycorrhizal symbiosis.