Font Size: a A A

Thermotolerance Of Photosynthesis In Salt-adapted Halophyte And Glycophyte

Posted on:2005-11-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:N W QiuFull Text:PDF
Abstract/Summary:PDF Full Text Request
Saline soil distributes abroad in the world. Few of researches focus on the response of plants grown in saline soil to heat stress frequently appeared in summer days. The thermotolerance of photosynthesis in five salt-adapted plants (Suaeda salsa, Atriplex centralasiatica, Artemisia anethifolia, Gossypium hirsutum and Triticum aestivum) was evaluated in this study and its possible mechanisms were analyzed.1 The effects of salinity (0, 100, 200, 400 mM NaCl for S.salsa, A. centralasiatica and A. anethifolia; 0,50,100,150 mM NaCl for cotton and wheat) on plants growth were different. Salt treatment resulted in a decrease in whole plant's dry weight of A. anethifolia, A. centralasiatica, wheat and cotton, but nbt in S.salsa. This result shows the different salt-tolerance in these five plants. Photosynthetic gas exchange and PSII photochemistry were analyzed in the halophytes and glycophytes exposed to salinity. Salt treatment did not show any obvious effects on the maximal efficiency of the maximal efficiency of PS II photochemistry (Fv/Fm), the efficiency of excitation energy capture by open PSII reaction centers (Fv'/Fm'), the photochemical quenching coefficient (qP), the efficiency of excitation capture by open PS II ( ps II). Though stomatal conductance and internal CO2concentration of S. salsa decreased a little, its CO2 assimilation rate of S. salsa increased with increasing salt concentration up to 200 mM NaCl and showed no decrease even at 400 mM NaCl. But CO2 assimilation rates of A. centralasiatica, A. anethifolia, wheat and cotton decreased significantly in parallel with obvious decrease in stomatal conductance and internal CO2 concentration with increasing salt concentration. These results suggest that the decrease in CO2 assimilation rate induced by salinity is not due to damaging PSII but associated with the closure of stoma.2 Higher thermostability of photosynthesis was found in salt-adapted leaves than that of in non-salt-treated plants of the five plants expbsed to a combination of high salinity (0-400 mM NaCl) and heat stress(36℃ ~48℃). At extremely high temperature (above 42 ℃ or 45℃), CO2 assimilation rates in control plants decreased nearly to zero, but the salt-adapted plants still presented a certain extent of CO2 assimilation capacity. On the other hand, theresponses of PSII photochemistry to heat stress were modified by salinity treatment. When temperature was above 42 °C, the declines in Fv/Fm, Fv'/Fm', qP and PSII were smaller in salt-adapted leaves than in non-salt-treated leaves. Though these five plants differ significantly in salt-tolerance and treated with different concentrations of NaCl, the increased thermostability of photosynthesis induced by salinity was found in all of these five plants. These results suggest that sonie protective effects on photosynthesis are inducedby salt treatment in these five plants, which can protect photosynthesis in salt-adapted plantsnot only against salt-stress but also heat-stress.3 The response of the antioxidant system to salt-stress and heat-stress was studied in the leaves of S. salsa. Activities of catalase (CAT; EC, ascorbate peroxidase (APX; EC, monodehydroascorbate reductase (MDHAR; EC, glutathione reductase (GR; EC, and contents of the antioxidants ascorbate and glutathione decreased with the increase of salinity, In contrast, the activity of dehydroascorbate reductase (DHAR; EC increased with the increasing salinity, while the activity of superoxide dismutase (SOD; EC increased only when treated with 400 mM NaCl. Similar results were found in the leaves of S. salsa treated with 42 C. Contents of MDA, aproduct of lipid peroxidation, in salt-adapted leaves of S. salsa were higher than in leaves of non-salt-treated plants exposed to 30℃ or 42℃. It is speculated that thermostability of photosynthesis does not depend on the antioxidant system in salt-adapted plants of S. salsa.4 The contents of proline and soluble sugar in salt-adapted leaves of S.salsa, A. centralasiatica an...
Keywords/Search Tags:salt-stress, heat-stress, halophyte, glycophyte, chlorophyll fluorescence, photosystem Ⅱ
PDF Full Text Request
Related items