Plant phenology, shoot growth and branching patterns in Mulinum spinosum (Apiaceae), a cushion-shrub of the arid Patagonian steppe of Argentina.

DAMASCOS, M. A.,; BARTHÉLÉMY, D.,; EZCURRA, C.; MARTINEZ, P.; BRION, C.

JOURNAL OF ARID ENVIRONMENTS

Elsiever

Lugar: Amsterdam; Año: 2008 vol. 72 p. 1977 - 1988

0140-1963

Although species of arid environments share physiological and morphological strategiesto reduce plant transpiration and protect leaves from excessive radiation and winddesiccation, they differ significantly in growth form, aboveground architecture,and rate of leaf turnover. We studied shoot growth pattern and leaf phenology inrelation to rainfall and air temperatures during the growing season in Mulinumspinosum, a cushion shrub having a broad distribution in the Patagonian steppe, a windy,temperate region with summer water deficit. The partitioning of aerial biomass inplants with different basal areas was also studied. Shoot formation began in latesummer when annual shoots (AS) produced temporary short shoots which restartedextension again in spring. AS exhibited continuous leaves senescence during the midand late growing season. Delayed branching of AS was related to total leaves senescenceon parent shoots in late summer. Fast leaf turnover reduces the transpiring area andwould allow plant re-hydration from soil water reserves, thus facilitating branchinginitiation. Plant annual biomass was reduced to a thin external layer, which becamedenser in plants of higher basal area, protecting buds and leaves in this arid and windyenvironment.Keywords: Annual shoots, Drought deciduous shrubs, Leaves survival, Plant biomass, Plant morphology, Temporary short shoots.