You can manage bookmarks using lists, please log in to your user account for this.
Media type:
E-Article
Title:
An Analysis of the Balance between Root and Shoot Activity in Lolium perenne cv. Melvina. Effects of CO2Concentration and Air Temperature
Contributor:
Nijs, Ivan;
Impens, Ivan
imprint:
Cambridge University Press, 1997
Published in:The New Phytologist
Language:
English
ISSN:
0028-646X;
1469-8137
Origination:
Footnote:
Description:
<p>This study investigated the mechanisms which control the partitioning between roots and shoots in plants subjected to changes in environment. Two types of analyses were used: firstly, an examination of the cost and revenue associated with investment in different plant parts, and secondly, a test of the principle of functional equilibrium between roots and shoots, i.e. whether root dry matter x root specific activity balances shoot dry matter x shoot specific activity. Measurements were made on individual plants of Lolium perenne in sunlit controlled environments, grown from germination to canopy closure under optimal nitrogen supply. At the final harvest, increased air temperature (+4<sup>⚬</sup>C above ambient) reduced whole-plant dry matter by 12% relative to the control, whereas elevated CO<sub>2</sub>mole fraction (700 μmol mol<sup>-1</sup>) led to a 38% gain. The combined treatment yielded an intermediate result (+19%). Plants grown at +4<sup>⚬</sup>C maintained balanced activity between roots and shoots throughout the experimental period, irrespective of CO<sub>2</sub>concentration. This required enhanced allocation to roots in young plants to compensate for a strong negative effect of higher temperature on root specific activity, which suggests that plants conserve balanced activity by adjusting dry matter partitioning. The extra cost involved with the adjustment at +4<sup>⚬</sup>C significantly enhanced the cost:revenue ratio of plant investment. In ambient temperature, the balance between roots and shoots departed from equilibrium, slightly at ambient but substantially at elevated CO<sub>2</sub>: the plants accumulated excess carbon relative to nitrogen, and this imbalance increased with plant age. At elevated CO<sub>2</sub>, the cost:revenue ratio increased in young plants but this was later reversed owing to loss of root specific activity, which explains the gradually declining CO<sub>2</sub>stimulation with time. The strategies in equilibrating root and shoot functioning observed in the different treatments are discussed in the light of whole plant performance.</p>