MODULATION OF GIBBERELLIN PHYSIOLOGY IN THERMOPERIODIC CONTROL OF SHOOT ELONGATION DOES NOT AFFECT PHOTOSYNTHETIC OR RESPIRATORY CAPACITIES

J.E. Olsen, R. Moe, J.A. Stavang
In commercial greenhouse production of a number of flowering plant species, a short temperature drop in the beginning of the light period or a lower day than night temperature (negative DIF = a negative temperature difference) may be used to reduce stem elongation. In our studies of the mechanisms underlying the responses, we have shown that thermoperiodic control of stem elongation involves a transcriptional regulation of the gibberellin (GA) metabolism in the model plant pea (Pisum sativum ‘Torsdag’). Particularly the levels of GA2-oxidase2 were strongly up-regulated in negative DIF or when temperature was dropped in light, but not in the dark. This resulted in decreased levels of active GA1. Furthermore, elongation growth of the la crys mutant in pea, which is elongated due to mutations in the DELLA genes encoding key compounds in GA signalling, was less sensitive to a negative DIF and temperature drop in light than the wild type. This suggests a role also of GA signalling in the response, and confirms that modulation of GA physiology is an important factor in control of shoot elongation by temperature-light interactions. We have also investigated effects of thermoperiodically regulated changes in GA1 levels on photosynthesis and respiration in pea. Our results suggest that thermoperiodic growth control by GA does not involve changes in photosynthetic or respiratory capacities. Thus, it appears that the main effect of reduced GA1 content under negative DIF is morphological changes due to reduced carbon allocation to stem tissue. Reduced biomass accumulation in negative compared to positive DIF appears to be a consequence of a combination of a direct effect of growth temperature on metabolism, and secondary effects of GA mediated changes in morphology.
Olsen, J.E., Moe, R. and Stavang, J.A. (2011). MODULATION OF GIBBERELLIN PHYSIOLOGY IN THERMOPERIODIC CONTROL OF SHOOT ELONGATION DOES NOT AFFECT PHOTOSYNTHETIC OR RESPIRATORY CAPACITIES. Acta Hortic. 907, 163-168
DOI: 10.17660/ActaHortic.2011.907.22
https://doi.org/10.17660/ActaHortic.2011.907.22
light, hormone, temperature, thermoperiodism, photosynthesis, respiration
English

Acta Horticulturae