CONSEQUENCES OF INCONGRUENCY IN DIURNALLY VARYING RESOURCES FOR SEEDLINGS OF RUMEX CRISPUS (POLYGONACEAE)

Citation
Jm. Cavenderbares et al., CONSEQUENCES OF INCONGRUENCY IN DIURNALLY VARYING RESOURCES FOR SEEDLINGS OF RUMEX CRISPUS (POLYGONACEAE), American journal of botany, 85(9), 1998, pp. 1216-1223
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
0002-9122
Volume
85
Issue
9
Year of publication
1998
Pages
1216 - 1223
Database
ISI
SICI code
0002-9122(1998)85:9<1216:COIIDV>2.0.ZU;2-1
Abstract
The incongruency of diurnally varying resources essential to plants ma y detrimentally affect plants early in their development as indicated by reduced water use efficiency and carbon gain. Typical diurnal patte rns of light and CO2 availability in a midsized temperate herbaceous o r forest gap were simulated in specially designed growth chambers. A s inusoidally varying CO2 treatment (400 ppm minimum, 800 ppm maximum) a pproximated the diurnal cycle of CO2 at the soil surface, while a stea dy-state CO2 treatment (600 ppm) with the same average CO2 concentrati on provided a control. Crossed with these two CO2 treatments were two light regimes, one with 3 h of high light (850 mu mol.m(-2).s(-1)) in the morning (west side of a gap), and the other with 3 h of high light in the afternoon (east side). All treatments received baseline low li ght (55 mu mol.m(-2).s(-1)) for 14 h during the day. Rumex crispus was selected as a model species because of its rosette leaves, which grow close to the ground where diurnal CO2 variation is greatest. The rela tive timing of diurnal variations in light and CO2 significantly affec ted seedling water use efficiency, carbon gain, and morphology. Total biomass, photosynthetic rates, daily integrated carbon, water use effi ciency, and leaf area were enhanced by morning exposure to high light. Seedlings that were exposed to peak values of light and CO2 incongrue ntly, i.e., those plants receiving intense afternoon light with diurna lly varying CO2, were detrimentally affected relative to control plant s receiving intense afternoon light with steady-state CO2. The results of this experiment indicate that the incongruent availability of requ ired resources-such as light and CO2-can detrimentally affect performa nce relative to when resources are congruent. These contrasting resour ce regimes can occur on the east and west side of gaps.