Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How Plants Sense Dry Air

16.04.2013
If the ambient air is very dry, plants need to protect themselves against excessive loss of water. For this purpose, they close special pores in their leaves. University of Würzburg researchers have explored how plants sense changes in humidity and translate this information into a signal.
Plants exchange gases, such as carbon dioxide and oxygen, with the atmosphere via special openings in their leaves, known as stomata. A ring-shaped arrangement of two so-called guard cells works like a swim ring: When the cells are swollen, they form an open ring; when the internal pressure drops, they shrink and the pore closes again.

In low humidity conditions, when there is a shortage of water, plants always face the following dilemma: Of course, they need to open their stomata as wide as possible in order to obtain carbon dioxide for photosynthesis, but at the same time they should close their stomata in order to prevent the risk of losing too much water in the form of water vapor.

Finely adjusted regulatory system of control signals

As a matter of fact, plants possess various partly overlapping mechanisms for ordering the stomata to open or close. The search for an ideal compromise under the respective conditions is subject to precise control. Professor Rainer Hedrich and his colleague, Dr. Peter Ache at the Department for Molecular Plant Physiology and Biophysics of the University of Würzburg, have gained new insight into this finely adjusted regulatory system and published their research in the journal Molecular Plant. The researchers used the well-understood genetic model organism Arabidopsis, also known as thale cress, in order to explore how the plants sense changes in humidity and translate this information into a chemical signal.

In a study published last November, Hedrich and Ache had already shown that guard cells can respond directly and independently to low humidity by producing the stress hormone abscisic acid (ABA). "ABA induces the guard cells to release salts from the cell inside. As a consequence, water flows outward and the guard cells shrink, which leads to stomatal closure," Rainer Hedrich explains.

Research on genetically modified plants

The two Würzburg researchers have now examined plants in which this signaling pathway is compromised due to mutation. "We worked with plants with a defect in an important switch gene," says Peter Ache. When compared with wild type plants, the activities of 100 genes were affected in each case by these mutations.

The researchers investigated which of these genes were preferentially expressed in guard cells and which of them responded to both the abscission hormone ABA and to dry air. They finally narrowed down the genes fulfilling all these criteria in both mutants to a total of four. "We consider these genes extremely important for stomatal response to reduced humidity," says Peter Ache.

The role of sugar molecules

One of these genes is also of crucial importance in the sugar metabolism of the guard cells. "It has long been our assumption that sugar plays an important role in stomatal closure due to dry air," Rainer Hedrich points out. Two scenarios are conceivable, which are not necessarily mutually exclusive:

"Firstly, the cell wall is amply equipped with sugar molecules, which attract water molecules. If this water is withdrawn due to dry air, the solubility of the cell wall sugars changes. This signal can be directly transmitted into the cell. Secondly, dry air may trigger the quick release of osmotically active sugars from the guard cells, leading to the release of water and to stomatal closure," the scientist explains.

The Würzburg plant biologists are going to tackle the open questions about the role of sugar in the dry air response mechanism by means of mutants with alterations in guard cell sugar metabolism and transport.

In their current study, for instance, Hedrich and Ache have already examined mutants in which the function of the sucrose synthase gen SUS3 is compromised. In their experiment, they investigated whether the genetic defect affects the ABA effect in low humidity conditions. This is in fact the case.

A new detail in a complex network

"The fact that some of the genes in the respective mutants are still activated, but others are not, supports our hypothesis that the respective proteins must be centrally involved in the humidity signaling pathway and that sugars play an important role in the process. Thus, we have made some headway in clarifying the whole network and identifying the possible humidity sensing mechanism," Peter Ache says with satisfaction.

Within the Bavarian research association ForPlanta, "Plants fit for the future", Hedrich and his colleagues have already used some other stimuli to induce stomatal closure and to analyze the respective changes in gene activity. They now intend to decipher the whole network with the help of bioinformatics. As to his future plans, Hedrich says: "When we have developed an understanding of stomatal closure due to dry air, we shall lock at the opposite stomatal response, namely the regulation of stomatal aperture".

"How do stomata sense reductions in atmospheric relative humidity?“, Hubert Bauer, Peter Ache, Florian Wohlfart, Khaled A.S. Al-Rasheid, Sophia Sonnewald, Uwe Sonnewald, Susanne Kneitz, Alistair M. Hetherington, and Rainer Hedrich. Mol. Plant, DOI:10.1093/mp/sst055

Contact
Prof. Dr. Rainer Hedrich, Department for Molecular Plant Physiology and Biophysics of the University of Würzburg , T +49 (0)931 31-86100, hedrich@botanik.uni-wuerzburg.de

Gunnar Bartsch | idw
Further information:
http://www.uni-wuerzburg.de

More articles from Life Sciences:

nachricht A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
21.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New bioimaging technique is fast and economical

21.08.2017 | Medical Engineering

Silk could improve sensitivity, flexibility of wearable body sensors

21.08.2017 | Materials Sciences

On the way to developing a new active ingredient against chronic infections

21.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>