| Growth and Metabolism of Three Introduced Summersed Plant Species in Relation to the Influences of Temperature and Light. (2002) | |||||||||
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| Under controlled experimental conditions, the influences of light and temperature on the growth and metabolism of Egeria densa Planch, Hydrilla verticillata Royle, and Myriophyllum spicatum L. were comparatively examined. Light was controlled at six levels ranging between 5 and 75 percent of full sunlight at peak solar noon. Water temperature was controlled at five levels ranging between 16 and 32 C. Growth considerations included morphology, biomass, and nutrition. Photosynthesis, respiration, and CO2 compensation points were determined to evaluate physiological differences in plant growth due to the effects of temperature and light. External morphology in these species was significantly affected by the experimental ranges of light and temperature conditions. Both low light and high temperature promoted extensive shoot elongation and associated canopy formation. Biomass production and carbon metabolism were affected more by temperature than light. Each of the species demonstrated metabolic acclimation to light over a broad range. Conversely, they were not strictly capable of acclimating to temperature, and the productivity of individual species was strongly responsive to this factor. Growth rate and the seasonal progression of senescence were interrelated in these species. Higher temperature stimulated growth and promoted a compression of the growth cycle. The relationship between photosynthesis and respiration (P:R) was appreciably reduced by senescence, but the CO2 compensation point did not reflect this condition. In the species examined, CO2 compensation points decreased with increasing temperature, suggesting adaptions to low free CO2 levels in the environment. (Author) | |||||||||
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