Seasonal variation in AMF colonisation, soil and plant nutrient content in gypsum specialist and generalist species growing in P-poor soils

Abstract

Aims Gypsum soils are P-limited atypical soils that harbour a rich endemic flora. These singular soils are usually found in drylands, where plant activity and soil nutrient availability are seasonal. No previous studies have analysed the seasonality of P nutrition and its interaction with the arbuscular mycorrhiza fungi (AMF) colonisation in gypsum plants. Our aim was to evaluate the seasonal changes in plant nutrient status, AMF colonisation and rhizospheric soil nutrient availability in gypsum specialist and generalist species. Methods We evaluated seasonal variation in the proportion of root length colonised by AMF structures (hyphae, vesicules and arbuscules), plant nutrient status (leaf C, N and P and fine root C and N) and rhizospheric soil content (P, organic matter, nitrate and ammonium) of three gypsum specialists and two generalists throughout a year. Results All species showed arbuscules within roots, including species of Caryophyllaceae and Brassicaceae. Root colonisation by arbuscules (AC) was higher in spring than in other seasons, when plants showed high leaf P-requirements. Higher AC was decoupled from inorganic N and P availability in rhizospheric soil, and foliar nutrient content. Generalists showed higher AC than specialists, but only in spring. Conclusions Seasonality was found in AMF colonisation, rhizospheric soil content and plant nutrient status. The mutualism between plants and AMF was highest in spring, when P-requirements are higher for plants, especially in generalists. However, AMF decoupled from plant demands in autumn, when nutrient availability increases in rhizospheric soil.

Gypsum endemics accumulate excess nutrients in leaves as a potential constitutive strategy to grow in grazed extreme soils

“…Indeed, generalists showed a higher accumulation of P in fine roots. This was probably because they have more root colonisation by arbuscular mycorrhiza fungi than endemics (Cera, Duplat, et al, 2021). More research on nutrient acquisition and growth of gypsum-adapted species is needed to fully understand the implications of the different nutritional strategies of gypsum endemics and generalists.…”

Nutritional strategy underlying plant specialization to gypsum soils

“…Compared to other alkaline soils with high Ca content, gypsum soils have higher Ca cation activity than soils with calcite (CaCO 3 ) as the main mineral component due to the higher solubility of gypsum ( Harmsen 1984 ). The result is higher Ca availability and lower P availability to plants due to precipitation of P as Ca 3 (PO 4 ) 2 (calcium phosphate) in soils ( Novozamsky and Beek 1976 ), which is added to the lower concentration of inorganic P in gypsum soils as compared to soils with calcite ( Cera et al 2021 a , b ). Gypsum soils only occur in drylands in arid, temperate and continental climates ( Eswaran and Zi-Tong 1991 ; Herrero et al 2009 ; Casby-Horton et al 2015 ), where low precipitation prevents gypsum from being leached from the soil, affecting plant performance and distribution ( Moore et al 2014 ; Escudero et al 2015 ).…”

“…We hypothesize that gypsophiles use sulphate as a counter anion to assimilate high Ca concentrations in cells and manage Ca accumulation and P depletion. Hence, plant specialization to gypsum soils would be related to plant specialization to alkaline soils with high Ca and low P, since gypsum soils are hypercalcic with remarkably limited P availability ( Cera et al 2021 a ). Similarly, calcicolous species display several physiological solutions to tolerate high Ca in cells and avoid interactions with P nutrition, as organic acid metabolism ( White and Broadley 2003 ).…”

“…Although there are few studies of plant-available P in gypsum soils, there are some recent studies that support this idea. Gypsophiles have less arbuscular mycorrhizal colonization than gypsovags ( Palacio et al 2012 ; Cera et al 2021 a ), and consequently have a lower reliance on the strategy of mycorrhizae for P acquisition, which is very costly in carbon. Furthermore, in contrast to gypsophiles, when gypsovags are grown in gypsum soil, they display lower P concentration than when they are grown in calcareous soil ( Cera et al 2021 b ).…”

Plant Growth Promoting Rhizobacteria (PGPR) and Arbuscular Mycorrhizal Fungi Combined Application Reveals Enhanced Soil Fertility and Rice Production

“…Meanwhile, the growth of the plant is enhanced due to its beneficial association with AMF. Thus, due to this increase in growth, the hyphae present in the soil absorb the maximum amount of nutrients [18][19][20][21][22][23][24][25]. Interconnected hyphae around the roots of a plant are reported to harm the roots of the nearby plant [26,27].…”