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Effect of Herbicides on Photosynthesis

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by Nate Nugent on 1 May 2013

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Transcript of Effect of Herbicides on Photosynthesis

Herbicides Herbicides & Agriculture Photosynthetic Inhibitors 4 Types of Inhibitors Photosynthesis Defining a Herbicide Two Types:
Selective
-Used for tillage and/or other
agronomic practices
-No-till or low-till systems
Nonselective
-Toxic to all plants
-Used for complete control on
plants growth Effects of Herbicides
on Photosynthesis Photosystem I (PSI) Inhibition
-Energy of sunlight captured by chlorophyll
-Diverts flow resulting production of reactive free radicals
-Within hours during bright sunlight
-Non-selective
Photosystem II (PSII) Inhibition
-Transfer energy through Photosystem II
-Herbicides bind to protein in transfer chain
- Some diversion of electrons but slower results
-Protoporphyrinogen Oxidase (PPO) Inhibitors
-Interphere with enzyme which produces chlorophyll
-No chlorophyll; leaves turn yellow
-Unused building blocks chlorophyll with oxygen form reactive free radicals
Carotenoid Biosynthesis Inhibition
-Prevent production of leaf pigments
Roles in protecting chlorophyll from being destroyed
Several different targets; one result Nate Nugent Types of Herbicides -Some interfere the growth of weeds and based on plant hormones -Selective kill certain targets -Kill unwanted plants -Widely used for agriculture and landscape turf management Contact Herbicides
- Kill only parts of plant touched
Systematic Herbicides
-Absorbed by foliage or roots; translocated to parts of plant
Spray Applied Herbicides
-Contact chemicals mixed with liquid & sprayed on fields
Soil Applied Herbicides
-Injected into the ground
-Three types
*Pre-Plant Incorporated Herbicides
*Pre-Emergence Herbicides
*Post-Emergence Herbicides -Process of plants using sunlight, carbon dioxide &
water to make sugars and oxygen
-Creates oxygen for animals & humans needed for
breathing
-Fairly complicated process within the plant cell
-Requires many enzymes and transfer electrons
-If disrupted for any reason, process will shut
down and plant will die
-Main target of herbicides known as photosynthetic
inhibitors Soil Applied
-Interfere with photosynthesis; blocking electron transfer
-Applied to soil to penetrate root and translocate
-Oldest leaves turn chlorotic first
-Plant becomes stunted & may die
Foliar Applied
-Block photosynthetic reaction; disrupt cellular membranes
-Penetrate leaves; tissue surrounding spray looses color
-Plant becomes stunted & may die Works Sited Infoplease.com (n.d.). Herbicide. Retrieved from http://www.infoplease.com/encyclopedia/science/herbicide.html

Lehman, Christine (2013). Herbicide Effects on Photosynthesis. Retrieved from http://www.ehow.com/about_6540515_herbicide-effects-photosynthesis.html

Paraquat Information Center (2013). Mode of Action: How Herbicides Work. Retrieved from http://paraquat.com/knowledge-bank/crop-production-and-protection/mode-of-action-how-herbicides-work

Pike, D and Hager, Aaron (n.d.). How Herbicides Work. Retrieved from http://web.aces.uiuc.edu/vista/pdf_pubs/herbwork.pdf

Science Daily (2012). Herbicides. Retrieved from http://www.sciencedaily.com/articles/h/herbicide.htm

Wessels (2009). How Herbicides Work. Retrieved from http://www.livinghistoryfarm.org/farminginthe70s/pests_03.html

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