PHLOEM EXUDATE COLLECTED VIA SCALE INSECT STYLETS FOR THE CAM SPECIESOPUNTIA-FICUS-INDICA UNDER CURRENT AND DOUBLED CO2 CONCENTRATIONS

A method was devised for collecting phloem sap from the CAM species Op untia ficus-indica using severed stylets of a scale insect (Dactylopiu s opuntiae), for which exudation could continue for up to 5 d. For bot h basal (planted) cladodes and first-order daughter cladodes, the conc entrations of sucrose and total amino acids in the phloem exudate were virtually constant over 24-h periods whereas the chlorenchyma osmolal ity had sizeable increases during the night under both current and dou bled atmospheric CO2 concentrations. Sucrose, total amino acids, and p otassium accounted for 56, 21, and 9%, respectively, of the osmolality of the phloem exudate, which was about 350 mOsm at the two CO2 concen trations; valine, isoleucine, leucine, tyrosine, glutamine, and lysine accounted for about 70% of the total amino acids. Doubling the CO2 co ncentration led to approx. 5% more sucrose, 560% more mannose and 17% less amino acids in the phloem exudate and also significantly increase d mannose, starch and glucomannan in the chlorenchyma. Atmospheric CO2 concentrations thus affected various solute properties in the phloem and the chlorenchyma of O. ficus-indica.