Controlling Plant Growth
After elaborate research and carrying out experimentations. I am now able to summarise what I researched and what information I have gathered. I then was able to produce two possible solutions to growing as many plants as possible in a small space.
Auxins
Firstly, auxins are a type of plant growth substance, or plant hormone, with morphogen-like characteristics. Morphogens are substances that govern the pattern of tissue development (how the tissue grows) via morphogenesis and the position of various specialized cell types within a tissue (where the cells grow). Therefore auxins, having alike characteristics to morphogens, are “in charge”, they coordinate many growth and behavioural processes of a plant’s life cycle, which is why they are essential for a plant’s body development.
Auxins have many effects on the plant body, for example they can increase the plasticity of young plant cell walls allowing cells to elongate and therefore direct the growth of a plant (as it only works on young/new plant cells). Auxins promote stem elongation and growth, resulting in the plant being able to compete for light and maximise the amount of light is can attain by reaching greater heights for photosynthesis. Auxins promote the formation of adventitious roots (branches off a primary root), this means the plant is able to find water and attain a larger amount of water for photosynthesis. They also promote the inhibition of leaf abscission (keep leaves from drooping), so that the leaves present a wider surface area to absorb more light for photosynthesis. They promote cell division, which frankly without the plant wouldn’t be living. Promoting lateral bud dormancy is another job of auxins; this means the growth of the bud has been delayed for a long time, meaning the auxins choose when the best time to allow it to finish developing will be. Finally they induce ethylene production; this is the hormone that regulates fruit ripening and the blossoming of flowers and even the shedding of leave.
The decisions of auxins aren’t simply random, they respond to the surrounding environment accordingly as I will explain further on. In a way you could liken auxins to the brain of a mammal, it influences movement, growth, reproduction and even nutrition to a certain extent as without auxins plants wouldn’t grow to absorb enough of the essential components for photosynthesis. The behaviour of auxins is also alike to that of neurones, sending signals or stimulating certain responses based on the surrounding environment.
Tropisms
As previously mentioned auxins are influenced by the environment, this is because they play a key role in tropisms. Tropisms can be either positive or negative but either way they are plants’ growth responses to external stimuli, more often when the stimuli are consistent (coming from one direction). Positive tropisms in plants are when the plant grows towards the stimulus, whereas negative tropisms are where the plant grows away from the stimulus. Tropisms are the opposite to nastic movements (which occur independently of the direction of stimuli); tropisms are directional and compensate for a plants inability to move as freely as would an animal when the environmental conditions become unfavourable. There are two types of tropism that influence a plant the most, these are phototropism and geotropism.
Phototropism
Phototropism is a tropism that responds to light stimulus (photo- is the Latin for light). Plant stems are mostly positively phototropic and in the few cases where they are negatively phototropic it is only weakly. A plant being positively phototropic is essential for its survival and is a beneficial adaptation. Without this characteristic plants wouldn’t be able to grow towards the light and compete with other plants to absorb a sufficient amount of light for photosynthesis. Leaves can individually be positively phototropic also maximising the amount of light a plant absorbs.