Removing leaves can bosst production

摘要

Removing the young leaves from cucumber plants can theoretically generate 7% higher production. In other words: an optimal leaf surface area in a greenhouse offers growers the opportunity to harvest more kilos. However, this is subject to a certain number of conditions. A plant needs leaves to be able to intercept light. Via photosynthesis the plant converts the light into the assimilates (sugars) needed for growth. The surface area of the leaves is expressed as the Leaf Area Index (LAI), which represents the number of square metres of leaf per square metre of greenhouse surface area. Below a LAI of 3 a plant intercepts more light as the LAI increases, as shown in the figure. For optimal growth, the available sunlight (and/or supplementary lighting)must be utilised to the maximum. This means allowing leaves to intercept as much light as possible, so that the light reaching the ground is restricted to a minimum. This requires a LAI of 3. If the LAI is higher than 3, then the extent of light interception and the corresponding photosynthesis in plants hardly alters. However, the lower leaves often start to turn yellow and the fruit quality deteriorates. If no leaves are removed from the growing cucumber plants, then the LAI will quickly exceed 3, asthe plants produce more leaves than strictly necessary. But with cucumbers grown on high wires, often so many leaves are removed that the LAI drops below 3. This is a not an ideal situation so the question arises, how can photosynthesis, and subsequently yield, be optimised.