What are Vernalization Requirements and Why Plants Need Vernalization?
Vernalization refers to the process of removing leaves from plants during the winter season. Leaves have many functions such as insulating the plant, regulating temperature and water content, providing food for insects and other animals, and protecting against frost damage. During cold weather or when temperatures drop rapidly, leaves lose their ability to perform these vital tasks. Leaves must therefore be replaced.
The most common method of replacing leaves is through pruning, which involves cutting off parts of the plant to make room for new growth. Pruning may also occur naturally due to environmental factors like drought or flooding. However, it is not always possible to do so with precision and speed, especially if the plants are small or growing close together. Other methods include mechanical means, such as the use of hoes or tractors to remove leaves. Mechanical removal of leaves is less efficient than pruning because it requires constant attention and labor.
Finally, there are biological means of leaf removal that require no human intervention at all. These include viruses and bacteria that attack leaves during the dormant period (when they are inactive).
In order to increase efficiency in leaf removal, some plants produce chemicals called auxins. These chemicals trigger stem growth on the lower parts of the plant, causing it to bend over and touch the ground. The shoots on top of the plant grow upward, allowing sunlight to reach the lower parts of the plant. With more sunlight reaching these parts, they can photosynthesize more efficiently. In addition, leaves that would have fallen off are now protected by being buried in soil.
Why Do Some Plants Have Different Vernalization Requirements?
These plants undergo vernalization before they can germinate. In plants that are vernalized, there are certain genes that are not expressed unless the plant has experienced a period of cold weather. This is called conditional necessity, and these genes code for proteins such as enzymes that are involved in various metabolic processes. The most important of these for our purposes are those involved in the synthesis of enzymes necessary for the breakdown of stored starches into simpler sugars. If vernalized, these plants can break down these starches in the winter so that they can grow when other sources of food are not available.
How Does vernalization Occur?
Most plants cannot grow until certain conditions are met. In order to grow, they need certain temperatures, light levels, and nutrient availability. These conditions are called thresholds, and a plant will not grow until these thresholds have been met. For example, many plants cannot grow until day length reaches a certain level. This is called the day-length threshold. Other plants require a certain temperature before they can grow. This is called the temperature threshold. There may also be other requirements that need to be met, such as the availability of certain nutrients. Some plants require specific levels of nutrients in the soil before they can grow, this is called the nutrient threshold.
Vernalization is a process in which the plant is exposed to a cold temperature for a period of time. This process mimics the conditions of winter and causes certain biochemical changes to occur within the plant. These changes include the synthesis of certain enzymes necessary to break down stored starches within the plant so that it can grow.
In order for vernalization to work, a plant must have certain genes turned on that code for certain proteins. These genes may be “turned off” in the summer, and not expressed at all. However, when exposed to cold these genes are “turned on”, and the necessary proteins are expressed. These proteins are then responsible for the biochemical changes within the plant.
How Are Some Plants Temperature Intolerant?
Some plants require a specific temperature in order to grow. If the temperature is too low, these plants will not grow and will be unable to photosynthesize. This type of plant is called temperature intolerant. These plants have adapted in such a way that they are only able to grow within a narrow range of temperatures. Outside of this range, they are unable to grow and photosynthesize.
In order to survive in areas that have inconsistent or limited supplies of water, some plants have adapted in such a way that they can survive long periods of drought. These plants enter a state of dormancy in which they stop actively growing and lowering their water consumption until more water becomes available. These plants will remain in this state until water is once again present in the soil, at which point they will resume growth.
Vernalization: Making a Seed Plant Grow
Most plants grow and develop using the energy from the sun in a process called photosynthesis. During this process, plants take carbon dioxide out of the air and convert it into food. This food is stored within the plant so that it can use it later to grow and develop.
Vernalization tricks a plant into thinking that winter has arrived. This causes a specific series of biochemical reactions to occur that are normally only active during the winter. One of these reactions is the breakdown of stored starches within the plant so that new growth can occur.
When spring arrives, a plant that has gone through the process of vernalization will begin to grow again using the energy from the sun just like it did the previous year.
Classes of Plants: How Are They Different?
Not all plants need the same things to grow. Some may need more sunlight than others, while some may require less water. This can be due to a variety of factors including where the plant naturally occurs or what the plant is adapted to. There are three main classes of plants:
Herbaceous: Plants that have a soft texture. The top of the plant can usually be eaten, such as the leaves of a lettuce plant or the root of a carrot. These plants usually die back in the winter and begin to regrow in the spring when there is more sunlight and warmer temperatures.
Woody: Plants that have a hard texture. These plants do not die back in the winter, but continue to grow with the seasons. They may turn a different color during the fall and lose their leaves during the winter, but they continue to grow due to a underground stem structure called a rootstock or stump.
Bulb: Plants that grow from a hardened bulb, such as an onion or a tulip. These plants store nutrients in their bulbs over the winter to use later when there is limited sunlight.
During the summer months, many plants will have flowers that attract pollinators. Pollinators are animals that carry pollen from one flower to another as a way of spreading seeds. After the flower has been pollinated, it will produce fruit. Fruits can be used as a food source during the winter after they have ripened.
Living Things Can Be Classified in a Variety of Ways
There are many different ways to classify living things. One easy way to do it is to split everything into two groups: plants and animals. This can be further split down into subgroups, such as aquatic plants, plants that fly, or plants that crawl.
The Kingdom Plantae contains all the plants. Some popular plants found here include:
Angiosperms: Plants that produce seeds inside a protective cover called a hull, such as an oak tree. These are the most common kind of plant and can be recognized by their flowers.
Gymnosperms: Plants that produce seeds without a hull. These plants tend to have cones.
Bryophytes: Also known as the moss family. This is the oldest plant group that still exists today. They are commonly found growing on rocks, trees, and in soil.
Fungi: The second largest kingdom of living things. These organisms do not produce their own food, but rather get their energy by absorbing nutrients from other plants or animals. There are three main groups of fungi: mushrooms, molds, and yeast.
Protozoa: Single-celled living things that are found in water.
Sources & references used in this article:
Vernalization, competence, and the epigenetic memory of winter by R Amasino – The Plant Cell, 2004 – Am Soc Plant Biol
Responses of wheat to vernalization and photoperiod by JL Davidson, KR Christian, DB Jones… – Australian Journal of …, 1985 – CSIRO
Vernalization and epigenetics: how plants remember winter by S Sung, RM Amasino – Current opinion in plant biology, 2004 – Elsevier
Relationships among vernalization, shoot apex development and frost tolerance in wheat by ITOM PRÁŠIL, P PrášIlová, K PáNková – Annals of Botany, 2004 – academic.oup.com