It seems that light is a physical medium that we have little control over in agriculture, but that is not entirely true. If we have greenhouse or indoor cultivation, light is a factor that we can control 90%, playing with liming or removing it depending on the development of the plant.
On the other hand, in an outdoor crop we have less capacity to act but we can play with pruning to get more light and aeration in the lower parts or intercrop larger crops with smaller ones.
In any case, light and luminosity is an important factor in the development of the plant, as we will see in some images that we will show you as we develop the article.
LIGHT IN INDOOR PLANTS
Whether in greenhouse cultivation, urban garden seedlings or indoor plants, there are different ways to manage light. Whether it is the placement of an awning, playing to put it on or take it off on hot days, or something more professional such as grow cabinets (for planting Cannabis sativa , germination of seeds, flowers, etc.), we have different ways of be able to increase the luxes or remove them.
Even on many occasions, the crystals act as diffusers to change the light path, as in Dutch glass greenhouses, and have an impact on the photosynthesis production capacity in horticultural crops .
Above all, in the central hours of the day, the difference in light and temperature received by the aerial part of the plant with respect to the lower leaves and stems is usually important.
Therefore, this has a negative effect on a decrease in photosynthetic performance . The upper leaves are capable of producing more photosynthesis than the lower ones, and the plant must manage the resources by mobilizing these sugars to the parts with the highest demand (roots or fruits).
This is negative for any plant. As it is a living being, it must be in continuous physiological adaptation to the heterogeneity of temperature and light currents.
THE EFFECT OF LIGHT ON DEVELOPING SEEDLINGS
Different development of absorbent hairs due to greater or lesser availability of light. Photo: Agricultural Homo
This image could be used by many fertilizer houses to position a product based on stimulating rooting . However, both melon seedlings have been grown under the same nutritional media.
[alert style = »yellow»] So? It turns out that the top plant, with a greater number of leaves and a much more abundant root production, has had much more light than the other plant, because it has been grown in a tray with fewer alveoli and has had more availability to it. . [/ alert]However, the plant below responds to the lack of light with a much longer stem, which is quite high energy consumption.
As we have already talked about in other articles about the C / N ratio and the energy disposition of sugar, the entire energy reserve has gone to generate a much longer stem to look for more light, and it has not had enough “strength” to produce roots.
As a curiosity, tell you that the plant above is 3 days less , but is much more developed.
LACK OF LIGHT IN CROPS
There are mathematical formulas to calculate the minimum radiation required from different crops. When it comes to horticulture and plant breeding, C3 (horticultural) plants are used to receiving at least 9000.10000 lux. It is known as photosynthetically active radiation or PAR radiation ( P hotosynthetically Active Radiation ), where it basically measures the photons necessary to avoid an excessively low photosynthetic rate.
We can see that in rainy areas with many cloudy days.
THE POINT OF COMPENSATION
It is known as the light-related compensation point when the photosynthetic rate equals the transpiration rate.
To explain it better, the plant loses the same amount of energy (measured in carbon or sugars) that it is capable of producing, remaining at a 0 ratio of energy production. Obviously, if this were to be continuous, the survival of the plant would be questioned, but fortunately this does not happen usually, at least in duration.
What you want to explain with this graph is that there is always a limit . The higher the light intensity, the more photosynthesis, up to a point. From here on, the plant is not capable of absorbing CO2 and the line becomes a plant.
Photosynthetic activity is based on the production of sugars or carbohydrates through respiration. When the energy of light is sufficient to initiate this activity and more oxygen is produced than is consumed in respiration, we say that the plant can develop.
This point begins when the energy of the light is sufficient to carry out photosynthetic activity to produce more oxygen than is required by the plant for respiration. From here, at high levels of light and net absorption of CO2, the respiration rate of the plant increases excessively, until it reaches energy level 0.
[alert style = »green»] Net photosynthesis = Photosynthesis – Respiration [/ alert]
THE DIFFERENT TYPES OF LIGHT THAT A PLANT RECEIVES
Light has different colors and each living thing can receive a different spectrum. For example, in the case of humans , we are able to see wavelengths from 380 to 770 nm, known as visible light .
Plants do not stray very far on this scale from humans as the range is from 400 to 700 nm. From here we can divide it into the following wavelengths:
- Violet (380 to 430 nm)
- Blue (430 to 500 nm): the photosynthetic process is most efficient when the wavelength range is in this caliber (like the melon seedling from before). Blue light is responsible for vegetative and leaf growth, and that is why it is so critical and necessary for the initial phases (germination, formation of new leaves, etc.). Many specialized seedlings play with this light to encourage more vigorous seedling development.
- Green (500 to 570 nm): plants absorb little the wavelength of the green spectrum. Many times it is irradiated and they return it, hence the color of the leaves is this, due to the chlorophyll pigment.
- Yellow (570 to 590 nm)
- Naranja (590 a 630 nm)
- Red (630 to 770): although the spectrum of plants is only up to 700 nm , it is important in regulating flowering and fruit production, helping to increase the thickness of the stem and branching of the plant.
From artificial light and depending on the apparatus used, we play with the following wavelengths:
Incandescent lamp: plays with the blue spectrum and generates a lot of light from the red spectrum.
Fluorescent lamps: they generate a large amount of blue, green and red spectrum, but especially blue.
High pressure sodium lamp: they produce red and green spectrum, so they would not be so interesting for agriculture except to regulate flowering and fruit setting processes.
Halogen lamp: generates a large amount of light in the green spectrum. Later red and blue to a lesser extent.
Led light : with this type of lamps you can play to generate the type of spectrum you want, depending on its manufacturing process.