PARENT SESSION
Oral Session #13: Plant Ecology: Light Relationships. Presiding: J. Rebbeck.
Monday, August 6, 2001. 1:00 PM to 4:30 PM. Hall of Ideas P&Q.
Ecophysiological consequences of contrasting microenvironments on the desiccation tolerant moss, Tortula ruralis.
Hamerlynck, Erik1, Tuba, Zoltan2, Henebry, Geoffrey3, 1 2 3
ABSTRACT- The ectohydric desiccation-tolerant (DT) moss Tortula ruralis forms extensive cover in fully exposed and shaded microenvironments throughout semi-arid Central European grasslands. Field and laboratory studies were made to determine the consequences of contrasting microenvironments on the growth, nutrient content, and chlorophyll fluorescence responses of this widespread DT moss, and reciprocal transplants were performed to see if the DT habit limits physiological acclimation. Shade-plant mosses had greater plant mass, total N and pigment contents, and had higher diurnal maximum PSII quantum efficiency (Fv/Fm) compared to sun-plants. Fv/Fm in transplanted sun-plants increased by 14%, while Fv/Fm in transplanted shade plants declined by 19% from original values; however, Fv/Fm in both transplants differed significantly from levels in untransplanted sun and shade plants. Thermal dissipation capacity (NPQ) was higher across a range of photosynthetic photon flux densities (PPFD) in shade plants and in both transplant treatments compared to sun plants. PSII excitation pressure (1-qP) and quantum yield of PSII (PSII) showed limited responses to transplanting, and only at lower PPFD. These findings suggest T. ruralis in shaded habitats experience extended favorable moisture periods that could prolong activity and increase both resource acquisition and integrated daily PPFD. Also, these DT plants may have greater physiological plasticity than previously realized, and this might aid persistence across these highly variable grassland systems.
KEY WORDS: chlorophyll fluoresence, desiccation tolerance, microenvironment, Tortula ruralis