For a significant portion of the year, the natural light levels in greenhouses often fall below the optimum for crop growth. Anne Elings, a Plant Physiologist at Wageningen University & Research, emphasizes that additional light in the greenhouse significantly enhances production and quality.
Photosynthesis, a complex process where plants convert CO2 and water into sugars, is crucial for plant nutrition. Sunlight or artificial light provides the energy needed for this process. Elings points out that the limiting factors in photosynthesis are typically the levels of CO2 and light. With water usually in abundance, the focus shifts to optimizing these two variables.
During low-light periods such as late autumn, winter, and early spring, light becomes the limiting factor. Elings suggests that increasing light in the greenhouse, achieved through assimilation lighting or coatings that enhance light incidence on the cover, is almost always beneficial. However, she notes the importance of maintaining a balance with CO2 levels, as an insufficient concentration can negate the positive effects of added light.
The interplay between light and temperature is another critical factor. While light influences sugar production, temperature dictates the demand for sugars in growing plants. Striking a delicate balance is essential. Too much light without a corresponding temperature increase can lead to slowed photosynthesis, affecting potential production. The challenge lies in the grower’s expertise to control this delicate balance, as calculation models offer guidance but cannot replace hands-on experience.
Contrary to light and temperature, humidity in the greenhouse air has a minimal impact on photosynthesis. Elings explains that extreme humidity conditions may cause plant pores to close, reducing CO2 absorption. However, maintaining an optimal balance between greenhouse climate, light, and CO2 remains a complex task for growers.
Addressing the question of whether a bit of additional light in winter makes a difference, Elings asserts its significance, particularly for fruiting vegetables planted in late autumn. The growth surge occurs as light levels increase toward spring, making the extra sunlight during low-light periods invaluable and, as Elings notes, essentially free.