Recovery rates of chlorophyll-fluorescence parameters in desiccation-tolerant plants: fitted logistic curves as a versatile and robust source of comparative data

Desiccation-tolerant plants vary greatly in the rate of recovery of chlorophyll-fluorescence parameters on re-wetting. This paper seeks general curves that will adequately describe the course of recovery, and quantify the variations in rate within and between species. Recovery of F-v/F-m is closely fitted in many species by a logistic curve, starting from zero, on a logarithmic time-scale (seconds to days). Such curves have three parameters, an asymptote at maximum F-v/F-m, a half-recovery time (T-0.5), and a slope constant (S). If F-v/F-m in dry material differs substantially from zero, four-parameter logistic curves can give a better fit. In either case, T-0.5 and S show wide ecologically-significant variation. Some species show anomalously high values of F-v/F-m, in the early minutes of recovery, alongside low absolute values of F-v/F-m; these invite further investigation. Logistic curves give good fits to the recovery in light of Phi(PSII), q(P), and photosynthetic CO2 fixation. The results provide the means to quantify 'high-inertia' versus 'low-inertia' strategies of desiccation tolerance, and to explore the factors influencing recovery time and rate, and the reasons for some discrepancies from the common course of recovery. There is substantial overlap in all parameters between the bryophytes and pteridophytes studied.