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Physiological Differentiation (physiological + differentiation)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Morphological and Physiological Differentiation among Vegetative Compatibility Groups of Verticillium dahliae in Relation to V. longisporum

JOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2001
K. Zeise
Abstract Twenty-four isolates of Verticillium dahliae from various geographic regions and host origins were assigned to vegetative compatibility groups (VCG) based on complementation between nitrate-non-utilizing (nit) mutants. The VCG assignment was associated with clearly distinguishable morphological and physiological characteristics. Most isolates of VCG 2B produced deep black colonies, small conidia (3.62 × 0.02 , m), and spherical microsclerotia. They exhibited polyphenol oxidase (PPO) activity, high sporulation rate in shake cultures, fluorescence on sanguinarine-amended PDA (snPDA) and excretion of dark pigment on Czapek Dox agar. The isolates assigned to VCG 4B had significantly longer conidia (4.73 × 0.04 , m), spherical microsclerotia and white, fluffy colonies due to enhanced production of aerial mycelium. They excreted only traces of dark pigment, exhibited PPO activity, did not fluoresce on snPDA and had limited ability to sporulate in shake cultures. Except for lacking PPO activity the only heterokaryon self-incompatible isolate (HSI) was similar to VCG 4B. Ten isolates of Verticillium longisporum from cruciferous hosts did not produce nit mutants. They had clearly longer conidia (7.41 × 0.05 , m), formed elongate microsclerotia, and only poorly sporulated in shake cultures. They did not excrete dark pigment, lacked PPO, and failed to fluoresce on snPDA. The results indicate a clear morphological and physiological differentiation not only between the two species V. longisporum and V. dahliae but also among the VCGs of V. dahliae. [source]

Minimizing energy expenditure facilitates vertebrate persistence on oceanic islands

ECOLOGY LETTERS, Issue 5 2002
Brian K. McNab
Abstract The characteristics of terrestrial vertebrates on oceanic islands are examined. They often include a reduced body size, a tolerance of conspecifics, flightlessness, a reduced basal rate of metabolism, and a propensity to enter torpor. On oceanic islands ectotherms frequently replace endotherms. These changes reduce the energy expenditure and resource requirements of vertebrates. Such reductions are permitted by the absence of mammalian predators and facilitate the survival of island endemics in the face of a restricted resource base and a variable environment through an increase in population size. Some insular species increase body size, but this occurs only when the resource base is large, due either to a fortuitously abundant resource, or to the absence of other species that exploit normally abundant resources. Some questions are posed to guide future work. They examine of the characteristics that permit species to disperse over water barriers, the conditions that require a reduction in resource use, the rapidity of response by immigrants to island conditions, whether supertramps show physiological differentiation with respect to island distance or size, and whether island size is absolute or relative to the size of the immigrants. [source]

Morphological and Physiological Differentiation among Vegetative Compatibility Groups of Verticillium dahliae in Relation to V. longisporum

Sexual dimorphism and seasonal changes of leaf gas exchange in the dioecious tree Ilex paraguariensis grown in two contrasted cultivation types

ANNALS OF APPLIED BIOLOGY, Issue 2 2009
M. Rakocevic
Abstract Yerba maté (Ilex paraguariensis, Aquifoliaceae) is a subtropical, evergreen, dioecious, South American tree. In one preliminary study, it was observed that the functional strategy of yerba mate females, aiming to finish reproductive process, was increased transpiration relative to photosynthetic rates compared with males, on self-shaded leaves. We hypothesised that the long-term gas exchange response of males and females can evolve independently of phenological stage and cultivation type. In this spirit, the primary aim of the study was to analyse the physiological sexual dimorphism of this species, evaluating fluctuations of gas exchanges related to microclimate and phenological stages. A field study was conducted on adult plants of yerba maté cultivated in monoculture (MO) and in forest understorey (FUS), and measurements carried out in situ on microclimate and leaf gas exchange parameters. The photosynthetic photon flux density that was attained at leaf level in FUS was reduced roughly 10-fold compared with that in MO. Various leaf age populations were observed during a 2-year period at 2-month intervals and grouped into four categories: young, young-fully-expanded, fully-expanded and old. Young and young-fully-expanded leaves were the most active in photosynthesis. Leaves of female plants showed greater photosynthetic rate than those of male plants, which was expressed on all leaf age categories in MO, but only during vegetative stages previous to flowering and fruit ripening. The photosynthesis of young-fully-expanded leaves of females grown in FUS was superior to males but only during winter growth pause. The stomatal conductance differed in relation to cultivation type and leaf age but did not show the sexual differentiation. Physiological sexual dimorphism in yerba mate is shown to be plastic, responding to environmental conditions. The cost associated to the reproduction of yerba maté could be most easily met showing physiological differentiation of both sexes. A higher reproductive investment of females might be compensated for by exhibiting greater leaf photosynthesis than males that occurs in vegetative stages that precede flowering and fruit ripening. [source]