关键词: 木霉菌剂, 枸杞, 耐盐能力, 光抑制, 非损伤微测技术

Abstract:

【Objective】This research aimed to investigate the effect of Trichoderma on salt tolerant ability of Chinese wolfberry (Lycium chinense), and to reveal the salt tolerant mechanisms in terms of in ion homeostasis, oxidative stress and photosystem II (PSII) performance.【Method】Chinese wolfberry was used as the experimental material, and Trichoderma agent was applied around roots. Salt treatment was carried out by irrigation with NaCl solution (300 mmol·L^-1), so as to compare the differences of biomass, K⁺/Na⁺, K⁺ and Na⁺ absorption and transport in roots, leaf oxidative damage and PSII performance in plants applied with and without Trichoderma agents under salt stress.【Result】Under salt stress, the biomass decreased less in plants applied with Trichoderma agents, indicating that Trichoderma could improve salt tolerance in Chinese wolfberry and alleviate the inhibition on growth. Under salt stress, Trichoderma alleviated the decline of photosynthetic rate and actual photochemical efficiency of PSII, inhibited the elevation of PSII excitation pressure, and aided in defending PSII photoinhibition. The decrease in Fv/Fm and the loss of PSII reaction center protein were relatively less in plants applied with Trichoderma agents under salt stress, confirming that Trichoderma alleviated PSII photoinhibition and protected PSII reaction center. Consistent with the result of photoinhibition, the oxidative damage was slighter in plants applied with Trichoderma agents according to lower leaf lipid peroxidation extent and H₂O₂ content. Under salt stress, the lower decrease in the efficiency that an electron moved beyond Q_A was noted in plants with Trichoderma agents application, while J step of chlorophyll a fluorescence transient (OJIP) did not obviously rise, indicating that Trichoderma protected the electron transporters at PSII acceptor side. Trichoderma also protected oxygen-evolving complex at PSII donor side of PSII, because the application of Trichoderma agent prevented a significant increase in variable fluorescence intensity at K step and an emergence of K step in OJIP curve under salt stress. Therefore, Trichoderma played a protective role for all PSII components, alleviated the decline of PSII performance index under salt stress, and improved PSII integral stability. Under salt stress, the lower Na⁺ content and higher K⁺ content were noted in roots and leaves in plants applied Trichoderma agents, indicating that Trichoderma inhibited the decline of K⁺/Na⁺ for maintaining ion homeostasis by reducing Na⁺ accumulation and K⁺ loss in roots and leaves. As the key mechanism for maintaining ion homeostasis, Trichoderma enhanced root Na⁺ efflux, improved root K⁺ uptake and promoted K⁺ transport to shoot in Chinese wolfberry under salt stress.【Conclusion】Trichoderma regulated the uptake and transport of Na⁺ and K⁺ in roots under salt stress, maintained ion homeostasis, reduced oxidative stress on PSII, and enhanced salt tolerant capacity in Chinese wolfberry and alleviate the inhibition on its growth.

Key words: Trichoderma agent, Chinese wolfberry, salt tolerance, photoinhibition, mon-invasive micro-test technology