Chlorophyll Fluorescence and Flowering Behaviour of Annual-Fruiting Raspberry Cultivars under Elevated Temperature Regimes

• Published in: European journal of horticultural science 2013-10, Vol.78 (5), p.193-202
• Main Authors: Gotame, T. P., Andersen, L., Petersen, K. K., Pedersen, H. L., Ottosen, C.-O., Graham, J.
• Format: Article
• Language: English
• Subjects: Chlorophylls; Flower buds; Flowering; Flowers; Fluorescence; Heat stress disorders; High temperature; Leaf area; Pigments; Plants
• ISSN: 1611-4426; 1611-4434

The effects of a seven day period with increased temperature from a standard level of 20 to 27,32 or 37 °C during flower initiation on apparent quantum efficiency (Fv/Fm), chlorophyll content and flowering behaviour in raspberry 'Autumn Bliss', 'Autumn Treasure', 'Erika', 'Fall Gold' and 'Polka' were investigated. The Fv/Fm decreased steadily from 0.82 to 0.70 on the seventh day at 37 °C in 'Autumn Bliss' and 'Fall Gold'. A significant diurnal variation in Fy/Fm, characterized by a midday depression and partial recovery in the evening was observed in 'Polka'. Plants of 'Autumn Bliss' exposed for seven days to 37 °C had 58 % less chlorophyll a as compared to those grown at 20 °C. The chlorophyll a/b ratio decreased to 20 % at 37 °C in 'Autumn Bliss', and 'Fall Gold'. The number of days to anthesis of the terminal flower was not significantly affected by the temperature treatments. The number of unopened axillary buds decreased at 37 °C in 'Autumn Bliss', 'Autumn Treasure', "Fall Gold' and 'Polka'. The percentage of flowering lateral shoots per plant decreased by 16 % at 37 °C in 'Autumn Bliss' whereas it increased by 7 % at 37 °C in 'Autumn Treasure' and 'Erika'. Seven days at 37 °C during flower induction delayed flowering in 'Autumn Treasure' and 'Erika' resulting in 20 % less unopened flowers at the time of registration compared with reference plants. Thus the negative responses of heat stress was reflected in a decreased midday Fv/Fm in all cultivais, while there was a remarkable difference in chlorophyll content and flowering behaviour among cultivars. These responses suggest that there is a difference of annual-fruiting raspberry cultivars in their inherent ability to adapt to heat stress.