Influence of mycorrhizal fungi on seed germination and growth in terrestrial and epiphytic orchids

Abstract

Epiphytes constitute over 70% of orchid diversity, but little is known about the functioning of their mycorrhizal associations. Terrestrial orchid seeds germinate symbiotically in soil and leaf litter, whereas epiphytic orchids may be exposed to relatively high light levels from an early stage of development and often produce green seeds. This suggests that seedlings of the two groups of orchids may differ in their responses to light and requirements for mycorrhiza-supplied carbon. The interactive effects of light, exogenous carbon and mycorrhizal status on germination and growth were investigated in vitro using axenic agar microcosms for one tropical epiphyte and three geophytic orchid species . The geophytic species strongly depended on their mycorrhiza for growth and this could not be substituted by exogenous sucrose, whereas the epiphytic species achieved 95% of the mycorrhizal seedling volume when supplied with exogenous sucrose in the dark. Mycorrhiza status strongly interacted with light exposure, enabling germination. Light inhibited or severely reduced growth, especially for the terrestrial orchids in the absence of mycorrhiza. For the first time, this study showed the parallel ecological importance of mycorrhizal fungi in overcoming light inhibition of seed germination and growth in both terrestrial and epiphytic orchids.

Stress tolerance of Xerocomus badius and its promotion effect on seed germination and seedling growth of annual ryegrass under salt and drought stresses

“…The improvement under stress conditions was markedly higher than that under non-stress conditions (P ≤ 0.05, Tables 4 and 5). Similar improvements in seed germination and seedling growth induced by mycorrhizal fungi inoculation with seeds have also been reported on Dendrobium officinale (Tan et al 2014) and other epiphytic orchid species (Alghamdi 2019). The results also showed that X. badius inoculation led to earlier seed germination and greater survival of seedlings compared with the non-inoculated seeds under non-stress and stress conditions.…”

Growth improvement of Lolium multiflorum Lam. induced by seed inoculation with fungus suspension of Xerocomus badius and Serendipita indica

“…In recent years, fungal inoculation implemented through seed sowing has been widely confirmed beneficial to crop seed germination and seedling growth (Vujanovic and Germida 2017). For example, promotion effects on seed germination induced by PGPF inoculation with seeds have been reported on barley (Murphy et al 2017), soybean (Waqas et al 2012), rice (Doni et al 2014), maize (Nayaka et al 2010), orchid (Alghamdi 2019), and ect. During seed germination, the symbiotically associated fungi degrade cuticle cellulose resulting in alleviated retardation effect, provide available carbon and produce phytohormones (especially gibberellins and indole acetic acid) (Hock 2012; Hossain et al 2017).…”

Progress and Prospects of Mycorrhizal Fungal Diversity in Orchids

“…Factors, such as rainfall and humus type, predict and affect the presence and richness of OMF-associated epiphytic orchids (Izuddin et al, 2019). Interestingly, although epiphytic orchids and terrestrial orchids exhibit different responses to light at the early growth, OMF have parallel ecological importance in overcoming the photoinhibition during germination and early growth (Alghamdi, 2017).…”