Co-Authors:
Philosoph-Hadas, S., Dept. of Postharvest Science of Fresh Produce, ARO, Volcani Center, Bet-Dagan 50250, Israel
Friedman, H., Dept. of Postharvest Science of Fresh Produce, ARO, Volcani Center, Bet-Dagan 50250, Israel
Meir, S., Dept. of Postharvest Science of Fresh Produce, ARO, Volcani Center, Bet-Dagan 50250, Israel
Berkovitz-SimanTov, R., Dept. of Postharvest Science of Fresh Produce, ARO, Volcani Center, Bet-Dagan 50250, Israel
Rosenberger, I., Dept. of Postharvest Science of Fresh Produce, ARO, Volcani Center, Bet-Dagan 50250, Israel
Halevy, A.H., Kennedy-Leigh Centre for Horticulture Research, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel
Kaufman, P.B., Dept. of Biology, University of Michigan, Ann Arbor, MI 48109, United States
Balk, P., ATO-DLO, P.O. Box 17, 6700 AA Wageningen, Netherlands
Woltering, E.J., ATO-DLO, P.O. Box 17, 6700 AA Wageningen, Netherlands
Abstract:
The negative gravitropic response of cut flower stalks is a complex multistep process that requires the participation of various cellular components acting in succession or in parallel. The process was particularly characterized in snapdragon (Antirrhinum majus L.) spikes with regard to (1) gravity stimulus perception associated with amyloplast reorientation; (2) stimulus transduction mediated through differential changes in the level, action and related genes of auxin and ethylene and their possible interaction; (3) stimulus response associated with differential growth leading to stalk curvature; (4) involvement of cytosolic calcium and actin cytoskeleton. Results show that the gravity-induced amyloplast reorientation, differential over-expression of two early auxin responsive genes and asymmetrical distribution of free IAA are early events in the bending process. These precede the asymmetrical ethylene production and differential stem growth, which was derived from initial shrinkage of the upper stem side and a subsequent elongation of the lower stem side. Results obtained with various calcium- and cytoskeleton-related agents indicate that cytosolic calcium and actin filaments may play essential roles in gravitropism-related processes of cut flower stalks. Therefore, modulators of these two physiological mediators may serve as means for controlling any undesired gravitropic bending.