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Soil salinity disrupts the development of wheat seedlings

The issue of increased soil salinity, a growing global problem in agriculture, has been the focus of recent research by scientists at Eötvös Loránd University (ELTE) in Hungary. The experts set out to investigate the effects of high salt concentrations on the development of wheat seedlings, particularly those germinating deep in the soil. 

This research is critical, given that salinization affects the livelihood of over one and a half billion people globally.

Plant greening 

The investigation revealed that the process of greening in wheat leaves, which includes chlorophyll biosynthesis and the development of chloroplasts, is significantly hampered when these leaves, growing in dark, saline soils, are suddenly exposed to various ions. This exposure can lead to stress and potentially the death of the seedlings.

“Many researchers have been investigating for a long time how high soil salinity inhibits the germination of most economically important crops and reduces their yields. However, no studies are available about how saline soils affect the leaves of plant seedlings developing from seeds sown deep into the soil according to agricultural planting protocols of many crops. This is even more surprising as salinization of croplands affects about one and a half billion people worldwide,” said senior author Katalin Solymosi, an assistant professor of Biology at ELTE.

The scientists discovered that sodium ions (Na+) have the most detrimental impact on plant greening, while potassium (K+) salts, such as those found in wood ash, and calcium chloride (CaCl2) are more benign alternatives for ice-melting purposes.

Focus of the study 

“In this context, it is particularly surprising that no study has so far investigated in detail how high salt concentrations affect the greening of wheat seedlings, even though it is obvious that the leaves of plants germinating in soil are directly exposed to soil salinity,” explained lead author Adél Sóti, a PhD student at ELTE.

“We found a simple method to investigate how salt affects the greening of plants. After 11 days of germination in complete darkness, for example in a closed box, leaf pieces of seedlings were first exposed to different concentrations of salt for 1.5 hours as a pretreatment and then illuminated in relatively low light to green them. Greening, that is the appearance or absence of green color after 16 hours of illumination, is readily visible to the eye and indicates the extent to which the saline solution was detrimental to the process.”

“With electron microscopic investigations we showed that the large and abnormal swelling of the water-containing inner space (called lumen) of the etioplast inner membranes did not occur during the application of only osmotic stress and was only observed in samples treated with high Na+ concentrations. Our comparative analyses showed that high concentrations (600 mM) of KCl, KNO3 or 300 mM CaCl2 also slowed down the greening, but did not induce such marked ultrastructural changes,” added Solymosi.

Study implications 

These findings highlight the significant role of soil salinity in affecting plant growth and point towards the need for more environmentally friendly approaches in areas such as road de-icing during winter. Moreover, they offer a foundation for understanding and combating the challenges posed by increasing soil salinity in agriculture worldwide.

The study is published in the journal Planta.

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