Ecophysiology of Amaranthus palmeri, a sonoran desert summer annual
Tóm tắt
Basic photosynthetic and water relations characteristics in relation to soil water availability were investigated in Amaranthus palmeri, a common C4 summer annual of the Sonoran Desert. Under conditions of high soil water availability, photosynthetic capacity exceeded 70 μmol CO2 m-2 s-1 at a leaf temperature optimum of 42°C, and photosynthesis was not light saturated at an irradiance of 2.0 mmol m-2 s-1 (400–700 nm). Leaves of A. palmeri exhibited diaheliotropic movements, allowing them to take advantage of their high photosynthetic capacity. In response to a long term drought cycle, both photosynthetic rate and leaf conductance to water vapor decreased, reaching minima at an approximate leaf water potential of-2.9 MPa. Active leaf osmotic adjustment appeared to play an important role in allowing leaves to maintain gas exchange activities down to these low leaf water potentials. The photosynthetic rate became light saturated at the lower leaf water potentials. Although the two parameters decreased in concert, the decreased photosynthetic rate was not due to increased stomatal diffusion limitations, since intercellular CO2 concentrations remained constant over the range of leaf water potentials. Instead it appeared that during the drought cycle, both intrinsic photosynthetic capacity and leaf protein content decreased as well. These results suggested a coordination of gas exchange parameters during long term drought such that the intercellular CO2 concentration remained constant.
Tài liệu tham khảo
Armond PA, Mooney HA (1978) Correlation of photosynthetic unit size and density with photosynthetic activity. Carnegie Inst Wash Yb 77: 234–237
Bell KL, Hiatt HD, Nikes WE (1979) Seasonal changes in biomass allocation in eight winter annuals of the Mohave Desert. J Ecol 67: 781–787
Björkman O (1975) Environmental and biological control of photosynthesis: inaugural address. In Marcelle R (ed), Environmental and Biological Control of Photosynthesis. Junk, The Hague, pp 1–16
Clark DD, Burk JH (1980) Resource allocation patterns of two California Sonoran Desert ephemerals. Oecologia 46: 86–91
Ehleringer J (1981) Leaf absorptances of Mohave and Sonoran Desert plants. Oecologia 49: 366–370
Ehleringer J (1983) Adaptations of annuals and perennials to warm deserts. In Chabot BF, Mooney HA (eds), Physiological Ecology of North American Plant Communities. Chapman and Hall, London (in press)
Ehleringer J, Forseth I (1980) Solar tracking by plants. Science 210: 1094–1098
Forseth IN, Ehleringer J (1982a) Ecophysiology of two solar tracking desert winter annuals. I. Photosynthetic acclimation to growth temperature. Aust J Plant Physiol 9: 321–332
Forseth IN, Ehleringer J (1982b) Ecophysiology of two solar tracking desert winter annuals. II. Leaf movements, water relations, and microclimate. Oecologia 54: 41–49
Forseth IN, Ehleringer J (1983) Ecophysiology of two solar tracking desert winter annuals, III. Gas exchange responses to light, CO2 and VPD in relation to long-term drought. Oecologia (in press)
Forseth IN, Ehleringer J, Werk KS, Cook CS (1983) Field water relations of Sonoran Desert annuals. Ecology (in prep.)
Körner C, Scheel JA, Bauer H (1979) Maximum leaf diffusive conductance in vascular plants. Photosynthetica 13: 45–82
Monson RK, Szarek SK (1981) Life cycle characteristics of Machaeranthera gracilis (Compositae) in desert habitats. Oecologia 49: 50–55
Mooney HA, Ehleringer JR (1978) The carbon gain benefits of solar tracking in a desert annual. Plant, Cell, Environ 1: 307–311
Mooney HA, Ehleringer J, Berry JA (1976) High photosynthetic capacity of a winter annual in Death Valley. Science 194: 322–324
Mulroy TW, Rundel PW (1977) Annual plants: adaptations to desert environments. Bioscience 27: 109–114
Osmond CB, Björkman O, Anderson DJ (1980) Physiological Processes in Plant Ecology. Springer-Verlag, New York
Robichaux RH, Pearcy RW (1980) Environmental characteristics, field water relations, and photosynthetic responses of C4 Hawaiian Euphorbia species from contrasting habitats. Oecologia 47: 99–105
Seemann JR, Downton WJS, Berry JA (1979) Field studies of acclimation to high temperature: winter ephemerals in Death Valley. Carnegie Inst Wash Yb 78: 157–162
Sesták Z, Catský J, Jarvis PG (1971) Plant Photosynthetic Production Manual of Methods. Junk, The Hague
Shreve F, Wiggins IL (1964) Vegetation and Flora of the Sonoran Desert. Stanford University Press, Stanford
Werk KS, Ehleringer J, Forseth IN, Cook CS (1982) Photosynthetic characteristics of desert winter annuals. Oecologia (in review)
Wilson JR, Ludlow MM, Fisher MJ, Schulze E-D (1980) Adaptation to water stress of the leaf water relations of four tropical forage species. Aust J Plant Physiol 7: 207–220