Super veg
Find out more about the food you eat.
To help plant breeders improve the potatoes and tomatoes we eat we need to understand the background to the qualities (e.g. flavour) we are interested in. Below are some of the qualities investigated by EU-SOL and how genes can affect them.
Processes and texture
We have seen how the texture of a tomato is dependent on the physical properties of the tomato. Here we will take one of these properties, cell wall strength, and explore how and why that changes during ripening.
Plant cell walls
The cell wall of a plant is in fact a highly complicated structure but it has three fundamental components.
- Tough cellulose fibres. Mostly parallel but interwoven, like fibres of a cotton thread, cellulose fibres provide much of the tensile strength of the wall.
- Molecules known as hemi-celluloses. By weaving around the cellulose fibres and bonding to them, hemi-celluloses help bind the wall together.
- Sugar molecules called pectins. Pectins form an additional network of connections within the cell wall in which the cellulose / hemicellulose network is embedded.
Diagram showing interactions between these elements in a plant cell wall
Photographer: LadyofHats. Copyright free
A plant cell wall is a bit like a microscopic version of a traditional cob wall. A cob wall is made by mixing clay based soil with straw and water). The straw (quite literally cellulose) provides toughness and a structure for the clay to cling to and the clay binds the straw together.
The construction of a traditional cob wall.
Photographer: Fountains of Bryn Mawr. Copyright: GNU
Ripening of a tomato
The strength of cell walls in a tomato is down to both the original construction of the walls and the ripening process. The structure of this cell wall and hence its strength are heavily modified during ripening. The affect of ripening on the physical structure and hence properties of tomatoes is of great interest to plant breeders and is the focus for the work on tomato texture within EU-SOL.
Broadly speaking the ripening of a tomato consists (in textural terms) of the breakdown or digestion of the cell walls and intercellular glue.
During ripening enzymes are secreted into the gaps between cells and attack the structure of the cell walls and the glue between them.
Different enzymes will control the breakdown of different aspects of the cell wall and intercellular glue. So for example one might assist the break down of cellulose strands in the cell wall and another one might break the connections between cellulose strands and the pectin between cells.
