Can Plants Drink Water from Minerals?

Where can we find water? The most obvious sources are bulk water (e.g. rivers, lakes, tap and bottled water), foods (e.g. fruits and vegetables), but then there are more obscure sources. Many minerals, such as gypsum, can hold water in their chemical structure. But can living organisms extract this water?

Palacio et al. (Palacio et al., 2014, Nat. Comm. 5:4660) set out to determine whether a plant that grows in and around gypsum can use water contained in the mineral. Helianthemum squamatum is a plant with shallow roots that remains active even during drought. How do you determine if a plant is using water from the soil or from gypsum? Well gypsum water has a different composition of hydrogen and oxygen isotope. An isotope is a different form of an atomic element – all atoms are made up of protons, neutrons and electrons. Elements differ based on the number of protons – hydrogen for example has 1 proton, while carbon has 6 protons – while isotopes vary in the number of neutrons. Special machines can determine which isotopes of different elements are present in things such as water.

Palacio et al. looked at the isotopes of hydrogen and oxygen present in soil water, gypsum water, and water contained in the plant tissue. They found that the plants used gypsum and soil water in about equal proportions during the relatively wet spring, however during the dry summer, the isotope composition of the water was extremely close to that found in gypsum. This tells us that H. squamatum can ‘drink’ water from gypsum so-to-speak. Furthermore, the authors speculate that the dehydrated gypsum could be rehydrated simply by moisture in the air, which means that water could be available for the plant even through long droughts.

What are the implications? Exobiology: Mars contains gypsum on its surface, which means that some plants may be able to survive Martian soils (but maybe not the atmosphere). Furthermore, our search for habitable planets outside our solar system might miss some candidates that might lack bulk water, but are covered in water-containing minerals such as gypsum. More down-to-Earth implications include understanding how life can survive very dry habitats and how we might be able to reclaim such land according to Palacio et al.

Stay safe and stay informed,
Joe

 

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Eating Fewer Resources

The food we eat has some kind of environmental cost – usually in the form of land to grow the food, water, fertilizer and pollution due to the machinery used. We tend not to think of which foods have a greater impact on the environment – growing crops requires land, water and (often) fertilizer. And it is easy to see how meat would incur a greater environmental cost – first we need to grow crops to feed the animals, then we need to provide additional water and land. But how much greater is the environmental impact of eating meat compared to plants? Further, how do meat sources compare in their environmental impact?

In a recent paper, Eshel et al. (Eshel et al., 2014, PNAS 111:11996–12001) compared the environmental impact of various animal food sources. They used a standardized method to compare dairy, beef, pork, poultry, and eggs in the United States. On the whole, Eshel et al. found that the animal-based portion of the American diet uses 40% of the US land area, water use is comparable to that of the American population, half of fertilizer use goes to animal food sources, and 5% of American greenhouse gas emissions are due to producing food from animals. The main conclusion is that beef production uses far more resources than the other major animal protein sources, which are generally equivocal in their resource requirements (see graphs below).

food source
Resource use per million calories consumed of animal products for A) land, B) water, C) greenhouse gas, and D) fertilizer.

Clearly reducing beef consumption could have a significant impact on reducing the environmental impact of one’s diet.  On further analysis, Eshel et al. find that beef uses 160 times the land as crops do per calorie produced.  It is then interesting to note that simply eliminating beef from your diet, without giving up meat consumption, can still dramatically reduce your environmental footprint. 

The article from Eshel et al. outlines how important it is to  determine all resource requirements of a food source in a comparable manner, to inform us as to how we can reduce the environmental impact of our diet.  This in turn can help to increase the sustainability of our agricultural systems moving forward.

Stay safe and stay informed,
Joe