Effects of arbuscular mycorrhizal fungus on photosynthesis and water status of maize under high temperature stress

Abstract

The purpose of this study was to investigate the effects of arbuscular mycorrhizal (AM) symbiosis on gas exchange, chlorophyll fluorescence, pigment concentration and water status of maize plants in pot culture under high temperature stress. Zea mays L. genotype Zhengdan 958 were cultivated in soil at 26/22°C for 6 weeks, and later subjected to 25, 35 and 40°C for 1 week. The plants inoculated with the AM fungus Glomus etunicatum were compared with the non-inoculated plants. The results showed that high temperature stress decreased the biomass of the maize plants. AM symbiosis markedly enhanced the net photosynthetic rate, stomatal conductance and transpiration rate in the maize leaves. Compared with the non-mycorrhizal plants, mycorrhizal plants had lower intercellular CO 2 concentration under 40°C stress. The maximal fluorescence, maximum quantum efficiency of PSII photochemistry and potential photochemical efficiency of mycorrhizal plants were significantly higher than corresponding non-mycorrhizal plants under high temperature stress. AM-inoculated plants had higher concentrations of chlorophyll a, chlorophyll b and carotenoid than non-inoculated plants. Furthermore, AM colonization increased water use efficiency, water holding capacity and relative water content. In conclusion, maize roots inoculated with AM fungus may protect the plants against high temperature stress by improving photosynthesis and water status. KeywordsArbuscular mycorrhiza . Chlorophyll fluorescence . Gas exchange . High temperature stress . Water status Abbreviations AM arbuscular mycorrhiza Ci intercellular CO 2 concentration E transpiration rate Fm maximal fluorescence Fo primary fluorescence Fv variable fluorescence Fv/Fm maximum quantum efficiency of PSII photochemistry Fv/Fo potential photochemical efficiency g s stomatal conductance Pn net photosynthetic rate PSII photosystem II RWC relative water content WHC water holding capacity WUE water use efficiency

Effect of cucumber mycorrhiza inoculation under low and high root temperature grown on hydroponic conditions

“…In the present experiment, Fv/Fm was significantly reduced in plants grown with 1,000 and 2,000 spores of mycorrhiza in low and high temperature root zones. In agreement with the present experiment, high temperature stress decreased Fv/Fm in non-mycorrhizal plants while mycorrhiza inoculation increased Fv/Fm under high temperature stress (Zhu et al 2011). Zhu et al (2011 stated that mycorrhiza alleviated the damage to PSII reaction center and the structural and functional distribution of photosynthesis.…”

“…Jinlv 3) dry weight reduced by low root temperature (12ºC) (Qiu-yun et al 2013). Zhu et al (2011) reported that maize shoot fresh and dry weight decreased by high temperature stress and mycorrhiza inoculation had no influence on plant weight under high temperature stress.…”

“…High temperature stress caused a reduction of chlorophyll in Zhu et al (2011) experiment and they stated that this may have been due to stopping chlorophyll biosynthesis or degeneration of chlorophyll under high temperature. Opposite to the present study, Zhu et al (2011) improved chlorophyll content via mycorrhiza inoculationand enhanced light harvesting. Furthermore, mycorrhiza increased carotenoids of maize and resulted in photoprotection of chlorophyll and photosynthesis apparatus (Wahid et al 2007).…”

Review on Arbuscular Mycorrhizal Fungi: An Approach to Overcome Drought Adversities in Plants

“…Ruiz Sánchez et al, (2010) found that AM symbiosis ameliorated the response of plants to drought by improving photosynthetic performance but mainly through the accumulation of the antioxidant compound glutathione, which was concomitant with a reduction in oxidative damage to membrane lipids and to low cellular levels of hydrogen peroxide. In maize, Zhu et al, (2011b) have reported low melondialdehyde content in mycorrhizal plants under drought stress which was 17.50% lower than that of 365 non mycorrhizal plants. In several systems, melondialdehyde has been shown to damage the membranes and disrupting the cell metabolism.…”

“…Uptake and movement of sufficient water to the evaporative surface helped the plants to maintain guard cell turgidity leading to opening of stomata for a gaseous exchange process (Nelsen and Safir, 1982). Through the opened stomata, more CO 2 enters the plants thereby the photosynthesis is improved in such plants (Zhu et al, 2011b). As the AM inoculated plants has the ability to mine water from soil, it could supply the water requirement of the evaporative surface and thus, the transpiration rate was also found to be significantly higher in fungal colonized plants (Roumet et al, 2006).…”