title: Thermoperiodic growth control by gibberellin does not involve changes in photosynthetic or respiratory capacities in pea.
abstract: Active gibberellin (GA(1)) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA(1) compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la cry(s), this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la cry(s) were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la cry(s) plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.
authors.affiliation: Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, N-1432 As, Norway.
authors.forename: Jon Anders
authors.initials: JA
authors.lastname: Stavang
authors.forename: Rolf Inge
authors.initials: RI
authors.lastname: Pettersen
authors.forename: Micael
authors.initials: M
authors.lastname: Wendell
authors.forename: Knut Asbjørn
authors.initials: KA
authors.lastname: Solhaug
authors.forename: Olavi
authors.initials: O
authors.lastname: Junttila
authors.forename: Roar
authors.initials: R
authors.lastname: Moe
authors.forename: Jorunn E
authors.initials: JE
authors.lastname: Olsen
mesh_terms: D020240:Apraxia, Ideomotor; D019069:Cell Respiration; D005875:Gibberellins / Q000378:metabolism*; D018532:Pisum sativum / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018547:Plant Stems / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction; D013696:Temperature
chemical_list: D005875:Gibberellins