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Title: BENDING ALTERS WATER BALANCE AND REDUCES PHOTOSYNTHESIS OF ROSE SHOOTS

Author
item KIM, SOO HYUNG
item SHACKEL, KENNETH - UNIV OF CALIF, DAVIS
item LIET, J - UNIV OF CALIF, DAVIS

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2004
Publication Date: 11/1/2004
Citation: Kim, S., Shackel, K.A., Liet, J.H. 2004. Bending alters water balance and reduces photosynthesis of rose shoots. Journal of American Society for Horticultural Science. 129: 896-901.

Interpretive Summary: In the past decade, "shoot-bending" (bending unmarketable stems down between the rows) has become a common cultural practice in commercial cut-flower rose production. Physiological effects of the bending on carbon and water balances of a rose plant have not been thoroughly investigated. This paper identified that bending reduces the rates of photosynthesis and transpiration as a result of lowered stem water potential of the bent shoot. The results will help researchers, extension specialists, and rose growers understand what will be happening in a rose plant when a shoot is bent.

Technical Abstract: Shoot-bending has become a standard cultural practice in cut-flower rose [Rosa hybrida L.] production. Physiological effects of shoot-bending on net photosynthesis (A), stomatal conductance (gs), transpiration rate and stem water potential (SWP) were investigated for cut-flower roses. With saturating light conditions, shoot-bending decreased rates of A, gs, and E in comparison with the rates prior to shoot-bending. A, gs and E of bent shoots were significantly lower than of the control shoots that were not bent. The differences in A between bent and control shoots decreased over time, disappearing within three weeks after bending. Leaves on bent shoots exhibited reduced SWP. Leaves projecting upwards on a bent stem were found to have higher A, gs, and E than those projecting sideways or downwards. This was probably due to the destruction of xylem vessels at the kink in the stem, serving the leaves attached to the lower side (compression side) of the bent stem. Our results support the hypothesis that hydraulic conductivity is reduced in bent shoots; that this is due to disturbed xylem tissues, and that reduced photosynthesis rates of bent shoots are a function of water status.