Definitions
What is a hormone?
An internal regulator that stimulates or inhibits plant growth activity.
How many types of tropisms are there? and what are they?
There are two types: a positive tropism (plant growth towards the stimulus) and a negative tropism (plant growth away from the stimulus).
How many main plant hormones are there? What do they do?
5 main hormones that act as signals, stimulating or regulating plant growth activity.
What are some essential factors for plant growth?
Light energy (sun), carbon dioxide (from the surrounding atmosphere), water, etc.
What is the meaning of the acronym pH?
pH stands for Potential of hydrogen.
What is a macronutrient?
Nutrients required in volumes larger than 1% of a plant's dry weight.
Why do Roots typically display a positive gravitropism?
They grow alongside gravity to help with anchoring and contact with water and minerals.
What are gibberellins? What is their main function?
One of the 5 main plant hormones; they stimulate cell elongation and seed germination
How are the majority of plant nutrients structured?
They are mostly structured as dissolved chemical compounds and ions.
What is an example of a micro nutrient that plants need to grow?
Chlorine, iron, boron, manganese, zinc, copper, molybdenum, etc.
What is Meristematic tissue?
A type of tissue in plant cells where plant cells are produced.
Is phototropism a plant’s growth response to gravity? If not, what does it mean?
No, gravitropism is a plant's growth response to gravity. Phototropism is a plant's growth response to light.
What is an auxin? Would a plant be able to grow without it?
A group of compounds that stimulate the elongation of plant cells. Without auxin, a plant would most likely not be able to fully develop into an adult plant, as auxin is involved in the growth process from when the plant is an embryo.
What soil pH are the majority of plants able to survive in?
Slightly acidic soils (pH 6-7).
What is the only known gaseous plant hormone?
Ethylene is the only known gaseous plant hormone.
What is a tropism?
a plant’s growth response to an external stimulus, deriving from one direction in the environment.
What does a decreased level of auxin (hormone) on one side of a plant do?
Less auxin causes cells to elongate, thus the side that is away from light becomes longer and causes the plant stem to curve in the direction of the light.
How does weed killer use synthetic auxin?
2,4-D, a synthetic compound, works by accelerating growth so much that a plant quickly uses up its food reserves and effectively starves to death.
What would happen to a plant without macronutrients?
The plant would die out, as macronutrients are essential for providing energy to the plant, and are needed in amounts greater than 1 percent of a plant’s dry weight.
What is an example of Thigmotropism and why would it occur?
Vines twisting around a fence, as it is a plant’s growth response to mechanical stimulants (touch).
What is a thigmotropism?
A plant’s growth response to mechanical stimulants (touch); can include contact with objects, organisms, or wind.
Would a plant be able to grow in zero gravity? How would it do so?
The plant would use the other types of tropism, phototropism and thigmotropism to orient growth. It would grow towards a light source (phototropism) and would still grow in response to mechanical stimulants (thigmotropism).
Because ripe fruits and vegetables are bruised easily during shipping, growers ship unripe fruits and vegetables. Once they reach their destinations, a treatment with ethylene is used to speed up the ripening process. How does the treatment speed up the ripening process of these fruits and vegetables?
Since ethylene is a gas, it can diffuse through the spaces between cells. It weakens the cell walls of unripe fruit and breaks down complex carbohydrates (such as starches) into simple sugars (such as sucrose and fructose). An increased exposure to ethylene after shipping will speed up the diffusion and weakening process, making the food ripen faster.
Would photosynthesis occur in a plant if the soil surrounding it was extremely acidic? Why or why not?
No, the plant would not survive as soil contains dissolved nutrients, necessary for growth, reproduction, and other cellular processes (photosynthesis). If the soil was very acidic, the nutrients in the soil would become less available, thus, killing the plant.
What are two hormones that would be useful when farming and distributing fruits and vegetables?
Gibberellins, as they promote the growth of taller, stronger plants and plants that flower early. Ethylene, as it weakens the cell walls of unripe fruit and breaks down complex carbohydrates into simple sugars, ripening fruits and vegetables earlier.