CO2 increase in the atmosphere augments tolerance of barley to salinity

Jul 07, 2008

In future, climate change will bring an increase in salty surfaces on the Earth and in the concentration of CO2 in the atmosphere. However, this higher CO2 has some positive effects on the physiology of barley plants and increases its tolerance to salinity. This is the conclusion of the PhD thesis of Ms Usue Pérez-López, defended at the University of the Basque Country (UPV/EHU).

Barley is one of the most important crops in the world. In fact 56 million hectares are under barley crops, making it the fourth most grown cereal worldwide. It is widespread over all the Continents, given that it adapts very well in different habitats. As with other plants, the correct development of barley depends on a suitable balance between the availability of water, nutrients and CO2. Nevertheless, it is predicted that there will be an increase in salinity in the soil in future, causing various imbalances which will result in a reduction in the growth of barley.

According to a number of authors, an increase in the CO2 level in the atmosphere may mitigate this growth decrease of the plants caused by high concentration of salts. However, research to date differs as regards results, and it is not known if the increased levels of CO2 can mitigate the negative effects of salinity on barley. This question was addressed by UPV/EHU teacher, Usue Pérez-López, in her PhD, presented at the University's Faculty of Science and Technology: Physiological responses of barley to the interaction of salinity and increased CO2. Prospects with climate change. Ms Pérez-López, a graduate in Biological Sciences with an Extraordinary Degree Award, carried out her work under the direction of doctors Alberto Muñoz-Rueda and Amaia Mena-Petite, from the Department of Plant Biology and Ecology. Dr. Pérez-López developed part of her research at the Department of Chemistry and Agricultural Biotechnology of the University of Pisa (Italy).

Greater rates of salinity and CO2

According to data supplied by the Food and Agriculture Organization of the United Nations (FAO), some 20% of irrigated arable surface area is subject to some level or other of salinisation, thus being hostile terrain for agriculture. Moreover, it is predicted that, in the near future, salinity will increase due to factors such as the expansion of irrigated zones, inefficient irrigation systems, the use of poor quality water and the increase in soil water loss due to greater evaporation as a consequence of high temperatures.

As a result of this increase in salinity the hydric state of barley plants will deteriorate and imbalances in their nutrition will occur due to excess sodium and chlorine (components of salt) and due to lack of potassium, calcium and nitrogen. In essence, the plant will produce less carbohydrates and proteins, which means a reduction in its growth.

The Intergovernmental Panel on Climate Change (IPCC) predicts that the CO2 concentration in the atmosphere at the end of the XXI century will double current levels. An increase contributed to by human activity through the combustion of fossil fuels and the destruction of forests. However, Dr. Pérez-López believes that barley could benefit from this increase, at least as regards mitigating the negative consequences of high salinity. Her research was based on the hypothesis that the greater the concentration of CO2, the higher the rate of photosynthesis, the hydric state of the plant is enhanced due to its lower transpiration (losing less water) and absorbs less toxic ions and is better protected against oxidation.

Dr. Pérez-López selected two varieties of barley (Hordeum vulgare cv Alpha and Hordeum vulgare cv Iranis) and studied their development, their nutritional and hydric states, their antioxidant system and carbon and nitrogen metabolisms, under high salinity and CO2 conditions, both separately and together.

Positive effects of CO2

One of the goals of Dr. Pérez-López's thesis was to see if the increased CO2 levels would enable less chlorine and sodium to be accumulated in the tissues of the barley plant. After undertaking a study of the various plant organs, she concluded that CO2 does not mitigate the accumulation of sodium in the tissues, despite the plant showing greater growth and less transpiration.

This lower transpiration, cause by the presence of high concentrations of CO2, does attenuate the loss of water through the plant leaves, due to the fact that the stomas are kept closed and the plant tissues are dehydrated to a lesser degree. Moreover, Dr. Pérez-López observed that plants growing under these conditions show greater root development, which augments the surface for water absorption. As a consequence, deducing from Ms Pérez-López's thesis, high levels of CO2 considerably enhances the hydric state of barley.

Dr. Pérez-López also asked herself if higher concentrations of CO2 in the atmosphere mitigate the reduction in growth caused by salinity. According to her PhD thesis, high concentrations of CO2 have a positive influence on the photosynthesis of the plant because, despite the fact that the plant keeps its stomas shut, the diffusion of CO2 between the exterior and the interior of the leaf is greater.

Finally, Dr. Pérez-López determined the oxidative stress level of the barley (the oxidation suffered by a plant due to high salinity), studied its antioxidant capacity, that is its defence mechanisms. Her conclusion was that high concentrations of CO2 alleviate this stress.

In short, Dr. Pérez-López's research concludes that the increase in CO2 enables greater growth of barley plants subject to saline conditions, thanks to the improvement in their hydric state and turgescence, but, above all, to the increase in photosynthesis.

Source: Elhuyar Fundazioa

Explore further: For the first time scientists map elevation changes of Greenlandic and Antarctic glaciers

add to favorites email to friend print save as pdf

Related Stories

Tide turns for shark fin in China

24 minutes ago

A sprawling market floor in Guangzhou was once a prime location for shark fin, one of China's most expensive delicacies. But now it lies deserted, thanks to a ban from official banquet tables and a celebrity-driven ...

New research reveals clock ticking for fruit flies

33 minutes ago

The army of pesky Queensland fruit flies that annually inflict many millions of dollars-worth of damage on the nation's horticultural industry may be about to see their numbers take a significant dive thanks ...

Apple's freshly sliced shares climb

4 minutes ago

Freshly split Apple shares closed at a high on Tuesday, with investors evidently betting the California company will debut popular new gadgets, perhaps a smart watch and an iPhone 6.

France fights back Asian hornet invader

14 minutes ago

They slipped into southwest France 10 years ago in a pottery shipment from China and have since invaded more than half the country, which is fighting back with drones, poisoned rods and even chickens.

Recommended for you

NASA sees Depression 12-E become Tropical Storm Lowell

22 hours ago

In less than 24 hours after Tropical Depression 12-E was born in the eastern Pacific Ocean it strengthened into Tropical Storm Lowell. NOAA's GOES-West and NASA's Aqua satellite captured infrared images of ...

Why global warming is taking a break

Aug 19, 2014

The average temperature on Earth has barely risen over the past 16 years. ETH researchers have now found out why. And they believe that global warming is likely to continue again soon.

User comments : 0