Over thousands of years, humans have "domesticated" wild type plants and animals through selective breeding. Examples from the plant world include the breeding of modern hybrid maize from teosinte, or the development of modern wheat from emmer.

As our knowledge of genomics and molecular technologies advances, we have developed much more precise and potentially more versatile ways to modify plants: genetic modification.

In these two lectures we have a brief look at what biotechnology actually means, and our challenges in the time of rapid population growth and climate change. Using the example of Bacillus thuringiensis toxin we explore the principles behind genetic modification, and follow that up with a brief description of the introduction of herbicide resistance into broad acre crops.

To conclude Plant Science in 2012, we move away from those input traits and take a look at Golden Rice, a genetically modified rice that produces beta-carotin in the grain. Golden Rice has the potential to save many thousands of children from blindness, and even death, caused by lack of vitamin A in the prevalent staple diet.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

Over thousands of years, humans have "domesticated" wild type plants and animals through selective breeding. Examples from the plant world include the breeding of modern hybrid maize from teosinte, or the development of modern wheat from emmer.

As our knowledge of genomics and molecular technologies advances, we have developed much more precise and potentially more versatile ways to modify plants: genetic modification.

In these two lectures we have a brief look at what biotechnology actually means, and our challenges in the time of rapid population growth and climate change. Using the example of Bacillus thuringiensis toxin we explore the principles behind genetic modification, and follow that up with a brief description of the introduction of herbicide resistance into broad acre crops.

To conclude Plant Science in 2012, we move away from those input traits and take a look at Golden Rice, a genetically modified rice that produces beta-carotin in the grain. Golden Rice has the potential to save many thousands of children from blindness, and even death, caused by lack of vitamin A in the prevalent staple diet.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

Over thousands of years, humans have "domesticated" wild type plants and animals through selective breeding. Examples from the plant world include the breeding of modern hybrid maize from teosinte, or the development of modern wheat from emmer.

As our knowledge of genomics and molecular technologies advances, we have developed much more precise and potentially more versatile ways to modify plants: genetic modification.

In these two lectures we have a brief look at what biotechnology actually means, and our challenges in the time of rapid population growth and climate change. Using the example of Bacillus thuringiensis toxin we explore the principles behind genetic modification, and follow that up with a brief description of the introduction of herbicide resistance into broad acre crops.

To conclude Plant Science in 2012, we move away from those input traits and take a look at Golden Rice, a genetically modified rice that produces beta-carotin in the grain. Golden Rice has the potential to save many thousands of children from blindness, and even death, caused by lack of vitamin A in the prevalent staple diet.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

The transition from water to land required plants to develop efficient transport pipelines for water and nutrients to the leaves, and for energy-rich carbohydrates (from photosynthetic carbon dioxide fixation) to tissues that require energy (e.g. roots, storage organs etc.).

Xylem and phloem are found together in vascular bundles and transport water (unidirectionally) and photosynthates (bidirectionally), respectively. While these vascular bundles, or steeles, are arranged in a circle in dicots, they are scattered throughout the stem in monocots. This means that monocots can not perform secondary, or thickness, growth.

Thickness growth in dicots is due to the activity of a secondary, or vascular, cambium that produces xylem towards the inside, and phloem towards the outside. Old phloem eventually dies and contributes to the bark which protects the active phloem.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

The transition from water to land required plants to develop efficient transport pipelines for water and nutrients to the leaves, and for energy-rich carbohydrates (from photosynthetic carbon dioxide fixation) to tissues that require energy (e.g. roots, storage organs etc.).

Xylem and phloem are found together in vascular bundles and transport water (unidirectionally) and photosynthates (bidirectionally), respectively. While these vascular bundles, or steeles, are arranged in a circle in dicots, they are scattered throughout the stem in monocots. This means that monocots can not perform secondary, or thickness, growth.

Thickness growth in dicots is due to the activity of a secondary, or vascular, cambium that produces xylem towards the inside, and phloem towards the outside. Old phloem eventually dies and contributes to the bark which protects the active phloem.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

A very important part of plant cells is located outside the cells themselves: plant cell walls.

Composed of numerous different building blocks (mostly polysaccharides, but also proteins and, particularly in cells that contribute to structural strength, lignin's), cell walls determine the shape of the cells and provide a counterforce to the osmotically generated turgor pressure.

In this lecture we look at the major polysaccharides that are found in the middle lamella, primary wall, and secondary wall, and a very simplified model of how we think the plant cell wall is organised. The role of lignin's as structural and water-proofing material is discussed briefly.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

A very important part of plant cells is located outside the cells themselves: plant cell walls.

Composed of numerous different building blocks (mostly polysaccharides, but also proteins and, particularly in cells that contribute to structural strength, lignin's), cell walls determine the shape of the cells and provide a counterforce to the osmotically generated turgor pressure.

In this lecture we look at the major polysaccharides that are found in the middle lamella, primary wall, and secondary wall, and a very simplified model of how we think the plant cell wall is organised. The role of lignin's as structural and water-proofing material is discussed briefly.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

So how does photosynthesis actually work?

In this lecture we explore the structures that capture light energy, photosystems 1 and 2, and how that light energy is harnessed to generate NADPH, and to build up a proton gradient across the thylakoid membrane. Just like in a hydroelectric plant, the proton gradient drives a little "turbine" that generates ATP. In this "light reaction" part of photosynthesis, light energy that is freely available from our sun is converted into chemical energy in the form of NADPH and ATP.

The chemical energy is then used in the Calvin-Benson cycle to fix atmospheric carbon dioxide. There are three main phases: actual fixation, catalysed by an enzyme referred to as Rubisco; reduction from an organic acid to an aldehyde which really is the first sugar; and recycling of the acceptor molecule.

Some plants employ a "carbon dioxide enrichment" process. The first fixation results in an organic molecule, most often malate, containing 4 carbon atoms - hence "C4 photosynthesis". Thanks to a very specialised leaf anatomy, the pre-fixed carbon dioxide is released in the bundle sheath cells, resulting in very high carbon dioxide concentrations which enable Rubisco to work very efficiently. The trade-off is a higher energy requirement.

A similar mechanism of pre-fixation with a temporal separation is used by CAM plants.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

So how does photosynthesis actually work?

In this lecture we explore the structures that capture light energy, photosystems 1 and 2, and how that light energy is harnessed to generate NADPH, and to build up a proton gradient across the thylakoid membrane. Just like in a hydroelectric plant, the proton gradient drives a little "turbine" that generates ATP. In this "light reaction" part of photosynthesis, light energy that is freely available from our sun is converted into chemical energy in the form of NADPH and ATP.

The chemical energy is then used in the Calvin-Benson cycle to fix atmospheric carbon dioxide. There are three main phases: actual fixation, catalysed by an enzyme referred to as Rubisco; reduction from an organic acid to an aldehyde which really is the first sugar; and recycling of the acceptor molecule.

Some plants employ a "carbon dioxide enrichment" process. The first fixation results in an organic molecule, most often malate, containing 4 carbon atoms - hence "C4 photosynthesis". Thanks to a very specialised leaf anatomy, the pre-fixed carbon dioxide is released in the bundle sheath cells, resulting in very high carbon dioxide concentrations which enable Rubisco to work very efficiently. The trade-off is a higher energy requirement.

A similar mechanism of pre-fixation with a temporal separation is used by CAM plants.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.

After finishing our quite extensive foray into leaf structure, function, and modifications, we finally start to look at what is arguably the main purpose of leaves: absorbing light energy, and using that energy to fix carbon dioxide.

In this lecture we will discuss the discovery of photosynthesis, and the general principle of the process.

Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.