PHOTOSYNTHETICA

Photosynthetica 2013, 51(1):75-84 | DOI: 10.1007/s11099-012-0080-0

Photosynthesis, energy partitioning, and metabolic adjustments of the endangered Cistaceae species Tuberaria major under high temperature and drought

M. L. Osório^1,2,*, J. Osório^1,2, A. Romano^1,2

¹ Institute for Biotechnology and Bioengineering, Centre of Genomics and Biotechnology IBB/CGB, Faculty of Sciences and Technology, Ed. 8, University of Algarve, Campus de Gambelas, Faro, Portugal

² Institute of Mediterranean Agricultural and Environment Sciences ICAAM, Faculty of Sciences and Technology, Ed. 8, University of Algarve, Campus de Gambelas, Faro, Portugal

In view of predicted climatic changes for the Mediterranean region, study of high temperature and drought impacts on physiological responses of endangered species regains relevance. In this context, micropropagated plants of Tuberaria major, a critically endangered species, endemic of Algarve, were transferred to a controlled-environment cabinet with day/night temperatures set at 25/18°C (Reference) or 32/21°C (HT). After 15 days of HT acclimation, some plants were subjected to progressive drought followed by rewatering. The enhancement of temperature alone did not affect water relations and photosynthetic rates (P _N) but the stomatal conductance (g _s) exhibited a 3-fold increase in comparison with reference plants. The maximum quantum yield of photosystem (PS) II (F_v/F_m), the effective quantum yield of PSII photochemistry (Φ_PSII), carotenoid (Car) and anthocyanin content enhanced, whereas the quantum yields of regulated (Φ_NPQ) and nonregulated (Φ_NO) energy dissipation decreased. Drought combined with HT reduced predawn leaf water potential to values of about -1.3 MPa, which had adverse effects on gas exchange and PSII activity. Values of P _N and g _s were 71 and 79% lower than those of HT plants. An impairment of photochemical activity was also observed: the decrease in Φ_PSII and the increase of Φ_NPQ. However, an irreversible photoinhibitory damage had not occurred. Carotenoid and anthocyanin content remained elevated and soluble sugars (SS) increased twice, whereas proline and MDA accumulation was not detected. On the first 24 h after water-stress relief, g _s, P _N, Φ_PSII, and Φ_NPQ did not recover, but SS returned to the reference level. Overall, T. major acquired an adequate capacity for a protection against the development of oxidative stress during drought and water recovery under HT. These findings suggest that T. major is prepared to deal with predicted climate changes.

Additional key words: anthocyanins; chlorophyll fluorescence imaging; energy partitioning; malondialdehyde; proline; soluble sugars

Received: June 25, 2012; Accepted: November 6, 2012; Published: March 1, 2013  Show citation