Effects of Glucose with 8-Hydroxyquinoline Sulfate or Aluminium Sulfate on the Water Balance of Cut «Sonia» Roses

Abstract

Glucose concentrations of 1%, 2% and 4%, combined with 50 mg 1 −1 8-hydroxyquinoline sulfate (8-HQS), elicited the following reactions in cut «Sonia» roses, as compared with water controls: - restricted initial transpiration, and less restricted solution uptake; - in the course of time slower decreases in these water-turnover rates; - a reversion in stomatal status: from initially most open in water and most closed in 4% glucose, to tightest in water and least tight in 4% glucose at the end. As the glucose concentration was higher, these effects resulted in: - ever greater water-uptake surpluses (with smaller total water turnover); - ever smaller light/dark weight fluctuations; - prolonged continuation of gain in fresh weight, with accordingly higher final bloom weigt; - better-looking blooms, at 4% almost indistinguishable from intact roses. From these observations and data from the literature it is concluded that, apart from effects on the energy and hormone levels, the ultimate net resultant action of glucose on the water balance is two-fold: - protection against excessive initial water loss, by rapid stomatal closure; - improved cellular water retention and solute-uptake capability, by metabolism-dependent preservation of membrane integrity. The most effective glucose concentration was found to depend on combinational interaction with the antimicrobial agent used. Whereas with 8-HQS 4% glucose — about the highest sugar concentration the cut «Sonia» rose can stand in continuous application — was best, with 200 mg 1 −1 aluminium sulfate similar results were obtained at 2% glucose. In addition, a strong tendency to axillary-bud sprouting indicated the latter combination to provide more favourable physiological conditions.