Differential protection mechanisms against water stress of Araucaria araucana seedlings from contrasting pluviometric provenances

PICCOLI PATRICIA; PAPÚ SOFÍA; BOLCATO LEONARDO; ROIG FIDEL A.

Santa Fe

Jornada; XXXIII Argentinian Meeting of Plant Physiology; 2021

CONICET

Water stress triggers acclimatization responses and/or cause damage in plants, which varies according to local adaptation of species to certain climatic conditions and stress levels. Ongoing climate change is projected to result in longer and more intense water stress conditions leading to an alarming increase in drought-induced forest decline. The aim of this study was to evaluate the physiological responses of Araucaria araucana pot-grown three-year old seedlings, originated in mesic environments (2000 mm year-1) (Verde Chico), intermediate (Villa Pehuenia) (1200 mm year-1) and xeric (Lonco Luan) (600 mm year-1). Plants were subjected to moderate and severe water restriction regimes and compared to well-watered controls during 120 experiment days. Origin dependent defense strategies against water stress effects were observed, evidenced by a differential behavior of xeric site seedlings under water stress: (i) the relative water content did not markedly decrease, while the growth was practically stopped, (ii) a higher leaf temperature and a lower decrease in matric potential was related to lower leaf transpiration, (iii) the photosynthetic pigments had a low degradation values, (iv) the monoterpene concentration remained low, (iv) the sesquiterpenes and total terpenes concentration dropped drastically, (v) seedlings produced a greater synthesis of the amino acid L-proline, and (vi) they did not exhibit a marked trade-off between growth and defense. This differential behavior would indicate that A. araucana is a species of great physio-ecological amplitude, allowing to classify xeric individuals as "water-saving" plants and mesic individuals as “water-wasters”. Those responses could be intensified under climate change context, which includes decreases on rainfall volume and increases of surface temperatures. Specifically an imbalance could occur in mesic sites plants, due to their greater water use.