LE3 .A278 2010

2010

Reekie, Edward

Acadia University

Bachelor of Science

Honours

Environmental Science

Earth & Environmental Sciences

The current rise in atmospheric CO2 concentration will have a direct positive effect on plant growth in that CO2 is a substrate of photosynthesis. The extent to which elevated CO2 enhances plant growth varies widely among species and environments. This research attempts to explain some of this variation by examining the effect of CO2 on representative shade- tolerant and - intolerant species. Plants preferentially absorb red light so plants grown in shade experience a low ratio of red to far- red light ( R: FR). R: FR is used as a developmental signal by plants. When grown in a low R: FR shade- intolerant plants grow tall and thin to avoid the shade of competitors. We hypothesize that a shade- intolerant plant will not respond as well to elevated CO2 at a low R: FR as a shade tolerant species because it will attempt to avoid shade by increasing allocation to height growth at the expense of roots. This will cause nitrogen and other mineral resources to become limited reducing response to elevated CO2. Plants were grown in growth chambers at ambient ( 380 ppm) elevated CO2 ( 760 ppm). Within each chamber pots were arranged under far- red and incandescent lamps to achieve a range of R: FR values that simulated full sun and shade light conditions. As predicted, the growth response of the shade- tolerant species to elevated CO2 was greater at a high R: FR than at a low R: FR, while the response of the shade tolerant species did not vary with R: FR. However, R: FR had no significant effect on root allocation. We conclude that although shade- tolerant and shade- intolerant species do differ in their response to elevated CO2, the mechanism behind this response is unclear.

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https://scholar.acadiau.ca/islandora/object/theses:672