Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New effects of herbicides on plants

22.01.2004


The aim of Navarre engineer Ana Zabalza Aznárez’s PhD thesis - entitled “The inhibition of the biosynthesis of amino acids in ramified chain and their use as a target-site for herbicides” - was to find out what effects herbicides produce on the metabolism of plants so as to enable a more rational use of them.

According to lecturer Zabalza Aznárez, herbicides have undergone considerable development since they began to be developed in the fifties of the last century in order to eliminate weeds which interfered with crop cultivation. Amongst the great variety of existing herbicides, affecting different aspects of the metabolism of plants, the authoress of the thesis has analysed those which inhibit the biosynthesis of amino acids in ramified chain.

These herbicides were discovered in the eighties and have experienced great success in the market, given their high effectiveness. Moreover, as they are applied in very small doses to crops, they have a minimum toxic effect amongst animals, given that inhibition of the biosynthesis of amino acids in ramified chain is a process which only takes place in plants and microorganisms, and is why these herbicides do not attack animals.



Nevertheless, Ms Zabalza has pointed out that, despite knowing the target-site of the herbicides that inhibit the biosynthesis of amino acids in ramified chain, its mechanism of action is still under investigation an the exact reason for the death of the treated plants is unknown. In her opinion, research on herbicides should reveal the reasons for the death of the plants treated with the compound, i.e. its mechanism of action.
This is precisely the aim of her PhD work, analysing two chemical groups of herbicides - sulphonylureas and the imidazolinones. The mechanism of action of these herbicides is one of the inhibition of activity of the first enzyme common to the biosynthesis pathway of the three existing amino acids in ramified chain - valine, leucine and isoleucine -: the acetolactate synthase enzyme (ALS).

Thus, the main aim of the PhD thesis was to investigate the mechanism of action of ALS activity-inhibiting herbicides on. To this end the pea was chosen as a target species for study, working in a growth chamber and under controlled conditions of temperature, humidity and period subjected to light. The effects of these herbicides were assessed in the first phases of the treatment, over the first seven days.

Lack of oxygen

The PhD concluded that one of the physiological effects provoked by the inhibiting activity on ALS, and which had not previously appeared in the literature, is that the plant roots thus treated with these herbicides activate a series of enzymes related to metabolism involving oxygen starvation, although the consumption of oxygen of these roots are not affected. In this way, an intensification is produced in the plant roots of the fermenting activity of the enzymes and of that of the alanine aminotransferase, an intensification triggered by a greater availability of piruvate, substrate that the ALS enzyme and these routes share, Ana Zabalza explains.

It has also been shown that plants treated with these herbicides have a greater energy load than those that are not thus treated. Likewise, the treated plants, on ceasing to produce amino acids in ramified chain, commence degrading the pre-synthesised proteins in order to obtain these amino acids and continue synthesising proteins, although this situation inhibits growth.

Another novel aspect arising out of the thesis was the study of an imidazolinone on the antioxidant systems and on the oxidative damage markers. Regarding this, the authoress concluded that a relation between oxidative stress and the mode of action of the inhibitors on ALS activity, although this oxidative stress does not appear to be involved in any major way in the lethality of the herbicides.

Sugars in the leaves

Apart from this, work was done on the more controversial effects of ALS-inhibiting herbicides: the accumulation of carbohydrates in the leaves of treated plants, an effect that is independent of whether the treatment is applied to the leaves or to the roots. The research revealed that, apart from the accumulation of carbohydrates in the leaves, these herbicides triggered the accumulation of carbohydrates in the roots of the plants, from which the authoress concluded that the inhibition of transport from leaves to roots is due to a lack of demand of the latter. Moreover, the results obtained indicate that the lack of growth of the plant is not due to a lack of respirable substrates.

Contact :
Iñaki Casado Redin
Nafarroako Unibertsitate Publikoa
inaki.casado@unavarra.es
(+34) 948 16 97 82

Iñaki Casado Redin | Basque research
Further information:
http://www.basqueresearch.com/berria_irakurri.asp?Gelaxka=1_1&Berri_Kod=389&hizk=I
http://www.unavarra.es

More articles from Agricultural and Forestry Science:

nachricht Cereals use chemical defenses in a multifunctional manner against different herbivores
06.12.2018 | Max-Planck-Institut für chemische Ökologie

nachricht Can rice filter water from ag fields?
05.12.2018 | American Society of Agronomy

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

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

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>