Response of photosynthesis and respiration of resurrection plants to desiccation and rehydration

Abstract

Using non-invasive techniques (CO2 gas exchange, light scattering, light absorption, chlorophyll fluorescence, chlorophyll luminescence), we have analysed the response of respiration and photosynthesis to dehydration and rehydration of leaves of the resurrection plants Craterostigma plantagineum Hochst., Ramonda mykoni Reichb. and Ceterach officinarum Lam. et DC. and of the drought-sensitive mesophyte spinach (Spinacia oleracea L.). The following observations were made: (i) The rate of water loss during wilting of detached leaves of drought-tolerant resurrection plants was similar to that for leaves of the sensitive mesophyte, spinach. Leaves of Mediterranean xerophytes lost water much more slowly. (ii) Below a residual water content of about 20%, leaves of spinach did not recover turgor on rewatering, whereas leaves of the resurrection plants did. (iii) Respiration was less sensitive to the loss of water during wilting in the resurrection plants than in spinach. (iv) The sensitivity of photosynthesis to dehydration was similar in spinach and the resurrection plants. Up to a water loss of 50% from the leaves, photosynthesis was limited by stomatal closure, not by inhibition of reactions of the photosynthetic apparatus. Photosynthesis was inhibited and stomates reopened when loss of water became excessive. (v) After the leaves had lost 80% of their water or more, the light-dependent reactions of photosynthetic membranes were further inhibited by rewatering in spinach; they recovered in the resurrection plants. (vi) In desiccated leaves of the resurrection plants, slow rehydration reactivated mitochondrial gas exchange faster than photosynthetic membrane reactions. Photosynthetic carbon assimilation recovered only slowly.

Desiccation Tolerance in the Resurrection Plant Craterostigma plantagineum. A Contribution to the Study of Drought Tolerance at the Molecular Level

“…As a consequence of the lower CO 2 availability, carbon assimilation is inhibited and ultimately photosynthetic capacity is lost. This observation is common to dehydration-sensitive and drought-tolerant species (Schwab et al, 1989). These physiological changes are reflected at the molecular level: The steady-state levels of transcripts related to photosynthesis are down-regulated in response to water stress, e.g.…”

Genetic and Physiological Analysis of Germination Efficiency in Maize in Relation to Nitrogen Metabolism Reveals the Importance of Cytosolic Glutamine Synthetase

“…It is likely that the increase in soluble Pro during germination was the result of the degradation of storage proteins, which generally have a high Pro content (Lea and Joy, 1983). However, it cannot be completely excluded that the increase in this amino acid is attributable to de novo synthesis as the result of a transient stress during the first stages of rehydration similar to that observed during salt and drought stress (Farrant et al, 1989;Schwab et al, 1989). Although our knowledge about the precise route of Pro synthesis in germinating seedlings is limited, its increase during seed germination has been reported in several species (Lea and Joy, 1983).…”

Photosynthetic carbon assimilation and associated metabolism in relation to water deficits in higher plants

“…Although physical damage to the mesophyll may occur, in some species the epidermis is removed relatively easily. Schwab et al (1989) and Dietz & Heber (1983) applied this technique to Ramonda mykoni and Primula palinuri, respectively, and showed most of the decline in A, induced by decreasing RWC from about 100 to 50%, was explained by stomatal closure. This is clear evidence of a Type 1 response.…”