Controlled long-term water deficiency and its impact on the fluorescence emission of tomato leaves during stress and re-watering.

摘要

We explored the potential of fluorescence ratios, based on multiple fluorescence excitation indices, as compared to chlorophyll fluorescence (ChlF) recorded with the pulse amplitude modulation (PAM) technique, for early and sensitive detection of water deficiency (WD) in tomato (Solanum lycopersicum) leaves. In this context, we hypothesized that the indices BFRR_UV (ratio of BF (blue fluorescence) to FRF (far-red fluorescence), both excited with UV-light), FLAV (logarithm of the ratio of red-excited FRF to the UV-excited FRF) and NBI (ratio of UV-excited FRF to the red-excited red fluorescence) of the multiple fluorescence excitation technique reveal the onset and intensity of WD in plants exposed to long-term WD, as well as during re-watering. For this purpose, three tomato genotypes were grown in the greenhouse under well-watered or long-term WD conditions. The decrease of the osmotic potential, relative water content and chlorophyll concentration as well as the increase in proline concentration confirmed the impact of WD leading to drought stress. ChlF recorded with the PAM technique showed significant differences between control and WD treatment in the relative apparent electron transport rate and the coefficient of photochemical quenching (qP). The indices BFRR_UV and FLAV significantly increased while the NBI significantly decreased during WD. As compared to the qP, the ratios BFRR_UV and FLAV provide information of equivalent quality concerning the genotype-specific responses to WD. Thus, the multiple fluorescence excitation technique establishes a valuable, fast and practical tool for the in situ monitoring of the physiological status of the plants without the need of dark adaption as required for the PAM recordings.