Vegetative desiccation tolerance of Tripogon spicatus (Poaceae) from the tropical semiarid region of northeastern Brazil

Abstract

The vegetative desiccation tolerance of Tripogon spicatus (Nees) Ekman was confirmed by its ability to recover the physiological functionality of intact plants previously subjected to extreme dehydration. Photosynthesis became undetectable when leaf relative water content (RWCleaf) achieved ~60%, whereas photochemical variables showed a partial decrease. Until the minimum RWCleaf of 6.41%, total chl decreased by 9%, and total carotenoids increased by 29%. Superoxide dismutase (SOD) activity decreased by 57%, on average, during dehydration, but catalase (CAT) and peroxidase (APX) activities showed no significant differences throughout the experiment. Malondialdehyde (MDA) content increased by 151%, total leaf and root amino acids decreased by 62% and 77%, respectively, whereas leaf and root proline decreased by 40% and 61%, respectively, until complete desiccation. After rehydration, leaves completely recovered turgidity and total chl contents. Carotenoids and MDA remained high, whereas SOD was 60% lower than the measured average measured before dehydration. With the exception of root amino acid contents, total amino acids and proline concentrations recovered completely. Gas exchange and photochemical variables remained substantially higher 4 days after rehydration, compared with the control. Besides increasing MDA, the overall physiological results showed that membrane functionality was preserved, leading to the vegetative desiccation tolerance of T. spicatus during the dehydration–rehydration cycle.