Plants Flashcards
Describe autotrophs and their role in plant growth.
Autotrophs are organisms that manufacture their own food, usually through photosynthesis, by absorbing carbon dioxide, water, and trace minerals.
Define primary growth in plants.
Primary growth refers to the elongation of plant cells at the tips of roots and shoots, involving cell multiplication through mitosis and growth in both length and width.
How do cells grow during primary growth?
Cells grow by filling their vacuoles with water, which causes elastic cell structures to stretch, leading to elongation.
What is the role of phytohormones in plants?
Phytohormones control various aspects of the plant life cycle, including growth, germination, and responses to environmental stimuli.
Explain the function of abscisic acid (ABA) in plants.
Abscisic acid (ABA) prevents germination within the fruit, helping to maintain seed dormancy during fruit maturation.
How do gibberellins (GA’s) affect seed germination?
Gibberellins initiate germination by promoting water absorption and breaking the dormancy of seeds.
What is the role of cytokines in plant growth?
Cytokines work with auxins to stimulate cell division and promote the growth and development of chloroplasts responsible for photosynthesis.
Describe the effect of ethylene on plants.
Ethylene stimulates the ripening of food and the abscission, or falling, of fruit and leaves.
How do plants respond to changing conditions without moving?
Plants respond to changing conditions by moving their organs in response to stimuli, a process known as tropism.
Define tropism in the context of plant growth.
Tropism is a directional growth response of plants to external stimuli.
Describe the long-term changes in plant cells due to environmental conditions.
Long-term changes in plant cells involve permanent alterations to the size and shape of the cells, allowing plants to adapt to favorable conditions for growth, such as high light intensity for photosynthesis, while avoiding unfavorable conditions.
Define auxins and their role in plant growth.
Auxins are water-soluble plant hormones produced in the tips of stems, shoots, and roots that promote cell growth by facilitating cell elongation, making cell walls more stretchable.
How do different concentrations of auxins affect plant growth?
Different concentrations of auxins result in varying rates of cell elongation on different sides of the plant, causing the plant to bend in one direction.
Explain the nastic response in plants.
The nastic response is a rapid, reversible change in turgor pressure of specific cells, resulting in non-directional movements that occur faster than tropic responses.
What is the role of K+ ions in the turgor pressure of guard cells?
K+ ions are pumped into guard cells, increasing turgor pressure, which controls the movement of water across the concentration gradient.
How does photoperiodism affect plant activity?
Photoperiodism is the regulation of plant activity based on the length of daylight, controlled by the phytochrome system.
Define phytochromes and their significance in plants.
Phytochromes are light-sensitive protein pigments in plants that exist in two forms and play a crucial role in regulating growth and development in response to light.
Describe the inactive form of phytochrome and its light absorption characteristics.
Pr (phytochrome red) is the inactive form that strongly absorbs red light.
How does sunlight affect the conversion of Pr to Pfr?
Sunlight, which contains a lot of red light, rapidly converts Pr to Pfr.
Define the role of Pfr in plant responses.
Pfr is the biologically active form that induces gene expression and the production of hormones for processes like flowering, bulb formation, and germination.
What happens to Pfr when it is exposed to far-red light?
When Pfr is exposed to far-red light, it absorbs it and gets converted back to Pr.
Explain the accumulation of Pfr during the day.
There is more red light than far-red light in sunlight, so more Pfr accumulates during the day compared to Pr.
How does the conversion of Pfr to Pr occur during the night?
During the night, active Pfr is slowly converted back to inactive Pr, allowing Pr to accumulate only if there is a long period of darkness.
Define photoperiod in the context of plant flowering.
Photoperiod is the length of the period of continuous darkness that determines whether or not a plant will flower.
