Nutritional strategy underlying plant specialization to gypsum soils

Abstract

Gypsum soils are amongst the most widespread extreme substrates of the world, occurring in 112 countries. This type of hypercalcic substrate has a suite of extreme physical and chemical properties that make it stressful for plant establishment and growth. Extreme chemical properties include low plant-available (N) and phosphorus (P) and high plant-available sulphur (S) and calcium (Ca), which impose strong nutritional imbalances on plants. In spite of these edaphic barriers, gypsum soils harbour rich endemic floras that have evolved independently on five continents, with highly specialised species. Plants that only grow on gypsum are considered soil specialists, and they have a foliar elemental composition similar to the elemental availability of gypsum soils, with high Ca, S and magnesium (Mg) accumulation. However, the physiological and ecological role of the unique foliar elemental composition of gypsum specialists remains poorly understood, and it is unknown whether it provides an ecological advantage over other generalist species on gypsum soils. This article reviews available literature on the impact of gypsum soil features on plant life and the mechanisms underlying plant adaptation to gypsum environments. We conclude with a hypothesis on the potential role of the nutritional strategy underlying plant specialisation to gypsum soils: Gypsum specialists primarily use SO42- as a counter anion to tolerate high Ca 2+ concentrations in cells and avoid P depletion, which is one of the most limiting nutrients in gypsum soils.

Calcium sulphate biomineralisation: Artefact of sample preparation?

“…These plants probably use other elements, such as magnesium, which has also been found to accumulate profusely in gypsum plants (Muller et al, 2017) to reduce the nucleation and growth kinetics of Ca‐sulphate crystals (Rabizadeh et al, 2017). This finding opens the window to new interpretations about the role of Ca‐sulphate accumulation in plants, such as the case of plant specialisation to gypsum soils (Cera et al, 2023), where gypsum endemics would accumulate Ca‐sulphate in oversaturation and not biomineralise.…”

Shipwrecked on the Rock, or Not Quite: Gypsophytes and Edaphic Islands

“…Thus, plants were differentiated into gypsophiles, gypsoclines, and gypsovags [35,83,84]. While the former group of plants includes specialists exclusive to gypsum soils, the latter corresponds to the category indifferent to soil nature, being common outside gypsisols [35,62,[84][85][86][87]. Among the gypsophytes, narrow-(nG) and wide-area gypsophytes (wG) can be distinguished according to their distribution area.…”