Photosynthetic and biochemical responses to soil water deficit and re-watering of two "long storage" tomato landraces

Long-storage tomato landraces are niche crops traditionally cultivated in southern Italy for drought tolerance and high nutritional and organoleptic quality of fruits. Nowadays, there is a growing interest in these crops as for exploiting biodiversity and the "Made in Italy" food production. We studied the physiological and biochemical performances of two landraces in response to soil water deficiency and re-watering. The potted-plant experiments were carried out in greenhouse during 2012 and 2013. During the first year, an intense water stress determined a decrease of stomatal conductance (gs) and net CO2 assimilation (A) along with an increase in both proline and ABA content, without any effect on photochemistry. In the second year, a more severe water stress leaded to a greater decline of both gs and A, and a reduction in photochemistry. During the re-watering, the full recover of gas exchanges and photochemistry, indicated the occurrence of efficient stomatal control and photochemical regulation, rather than impairment of photosynthetic apparatus. The activity of poly ADP-ribose polymerase (PARP), a key regulator of the energy homeostasis during stress conditions, showed during the first cycle of stress an evident increase, followed by a decrease. Re-watering, instead, produced a new non-expected increase of activity, which returned to control values during the second cycle of water stress. The two tomato landraces succeeded to cope with water stress by a useful synergy of biochemical and physiological regulatory mechanisms.This work was financially supported by "CISIA for the Made in Italy" Project of the National Research Council of Italy.