Estimation de la capacité photoautotrophique de vitroplants de porte-greffe de vigne (var. Gravesac): mise au point d'un système de mesure de la photosynthèse nette de vitroplants
DOI:
https://doi.org/10.5073/vitis.1996.35.73-78Keywords:
in vitro, Vitis, rootstock, photosynthesis, respiration, autotrophyAbstract
La capacité photosynthétique de vitroplants de vigne (var. Gravesac) a été déterminée à l'aide d'un dispositif de mesures des échanges gazeux en circuit ouvert. L'activité photosynthétique et la respiration de la plante sont importantes en culture in vitro. La photosynthèse nette maximale est de 2 µmol m-2 s-1 a 500 µ11-1 de CO2. A 350 µ11-1 de CO2 la photosynthèse est de 1,6 µmol m-2 s-1. La respiration a l'obscurité est de 0,018 µmol s-1 g-1 de poids sec total. La quantité totale des sucres solubles dans le milieu de culture reste constante pendant les deux mois de culture. Le saccharose est totalement hydrolysé en glucose et en fructose. Les vitroplants de Gravesac ne prélèvent pas de sucres dans le milieu, ce qui confirme leur degré élevé d'autotrophie dans ces conditions de culture. La comparaison entre les échanges gazeux de vitroplants et des plantes cultivées en serre met en évidence une réduction de 80% de l'activité in vitro.
Evaluation of the photoautotrophic ability of Vitis plantlets (rootstock var Gravesac): Set-up of a special open flow gas exchange system
The photosynthetic ability of Vitis rootstock plantlets (var. Gravesac) was estimated in vitro with an open flow system specially designed for in vitro culture. CO2 response curves were established and respiration was also measured. The maximum net photosynthetic rate, reached at 500 µ11-1 of CO2, is 2 µmol m-2 s-1. At 350 µ11-1 CO2 the photosynthetic activity is 1.6 µmol m-2 s-1. The dark respiration rate is 0.018 µmol s-1 g-1 of total dry weight. The total amount of soluble carbohydrates in the medium remains the same whether plantlets were present or not. In the medium with plantlets, the sucrose is entirely hydrolysed in glucose and fructose within two months. No carbohydrate uptake from the medium was recorded indicating an autotrophic behaviour. Measurements of CO2 exchange were also performed at leaves of plants cultivated in a greenhouse. The photosynthetic activity of in vitro plants accounts only for 20% of the level of greenhouse-grown plants.
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