PHLOEM SAP COLLECTION FROM LETTUCE (LACTUCA-SATIVA L) - CHEMICAL COMPARISON AMONG COLLECTION METHODS

The chemical composition of phloem sap from lettuce, collected by thre e different methods, was compared. Phloem sap from stylectomy samples contained sucrose and 14 amino acids. Honeydew and EDTA chelation samp les showed considerable breakdown of sucrose into fructose and glucose , several additional amino acids, and large differences in relative co ncentrations of amino acids, when compared to stylectomy samples. Hone ydew contained considerable amounts of other oligosaccharides, and few proteins in low amounts, while EDTA showed many proteins, HPLC chroma tograms showed numerous unidentified secondary plant compounds in hone ydew and EDTA samples. Comparison of phloem sap samples from near-isog enic susceptible and resistant lines showed no relation of phloem sap composition with monogenic resistance to the aphid Nasonovia ribisnigr i.