Coatings enable maximum efficiency of photosynthesis

The more light, the better the yield. But at a certain moment the leaves at the top of the crop have reached their maximum capacity. Therefore it is better to distribute the available light throughout crop. That can be seen in the photo response curve.

For each crop, higher light intensity leads to more net photosynthesis within a certain section (see chart). The rise in this section is almost proportional to the increase in the light level. But at a given moment it stops. Then the efficiency flattens out and can even fall if the light increases further. Then more light is harmful to the plant. The relationship between light intensity and photosynthesis is different for each crop, as well as the point where the graph bends, but the shape of the graph is always the same. It starts at a point where net photosynthesis at low light intensity is negative. That occurs because the plant always respires, in other words it uses assimilates (sugars).

If there is insufficient light, it is at the expense of net assimilates because then consumption is greater than production. But when the light level rises enough sugars are very quickly produced again. This is the steep part of the graph where the efficiency increases. This is followed by the flat part and eventually the part where the line bends downwards and the efficiency decreases again. Decreasing efficiency, or even damage to the photosynthetic mechanism mostly occurs in countries where light intensity is very high. But also in temperate regions, such as the Netherlands, shade-loving plants can receive so much light that they become damaged.

Better light distribution
When the radiation is high the leaves at the top of the crop are at their maximum capacity. Extra light doesn’t result in more photosynthesis and can even be harmful. Meanwhile many leaves at the bottom of the crop are a long way off their maximum production capacity. They would benefit greatly from more light. The chart makes it easy to understand the effect of coatings. A solar reflecting coating such as ReduSol ensures that the upper leaves don’t enter the part of the response chart where more light becomes harmful, therefore they continue to produce optimally. Also, the reflection of light ensures that the plant temperature doesn’t become too high. ReduHeat focuses specifically on this last point: prevention of an excessively high plant temperature.

When using ReduFuse light is better distributed throughout the greenhouse, both horizontally and vertically. Due to the vertical distribution, the upper leaves receive less light and therefore return to the steep part of the curve instead of the flat part. Leaves at the bottom of the crop receive more light as a result of the coating and their efficiency makes a move up the line on the graph. Both the leaves at the top and the bottom of the crop will function better. Together this leads to higher productivity when the light is diffuse compared with ordinary light. Thus the better distribution of light improves the total efficiency of photosynthesis. The aim is to have as many leaves as possible functioning in the steep part of the curve.

For more information
Mardenkro The Netherlands
Geerstraat 8
5111 PS Baarle-Nassau
The Netherlands
T: +31 (0)13 507 70 69
sales@redusystems.com
www.redusystems.com