PHOTOSYNTHETIC ACTIVITY, GROWTH AND PRODUCTIVITY IN A S-TRIAZINE-RESISTANT BIOTYPE OF SOLANUM-NIGRUM

Triazine-resistant (R) and -susceptible (S) biotypes of Solanum nigrum were compared in terms of photosynthetic activity and ecological fitn ess. Chlorophyll fluorescence assays showed lower electron transport r ates in R biotypes than in their S counterparts. For photosynthetic ac tivity, R biotypes showed lower rates than S biotypes in photosystem I I (PSII) electron transport (R/S ratios of 0.5), this apparently being correlated with an increased (F-I-F-O)/(F-P-F-O) ratio (fluorescence at O, I and P levels of the rapid rising phase of the induction curve) . Similar rates were observed, however, both in photosynthetic electro n transport by thylakoids and in photosynthetic oxygen evolution at di fferent light intensities, by leaf discs. The S-biotype of S. nigrum e xhibited significantly higher growth parameter values (plant height, a rea and number of leaves as well as root, stem and leaf dry weight), b ut the reverse held true for productivity parameters (seed numbers and 100-seed weight), where values for the R-biotype were significantly h igher.