biology exam 1
what is the role of expansins in cell and plant growth? how are expansins activated?
Pressure of the vacuole and the expansion.. There is a massive bag in the cell that creates a uch of water and once it gets to the membrane it makes it more acidic and that activates it. H+ ions goes across breaking down the cell wall. It will rebuild it bigger and it can take in more water making it grow.
what is the function of guard cells and how do they contribute to the function of the leaf?
Guard cells allow the stomata to be the open during wet conditions and to close when conditions are dry. This prevents the plant from losing too much water. The wax helps prevent the water from leaving the leaf.
Explain why nitrogen fixation important for plants.
Nitrogen fixation is the process by which atmospheric nitrogen is combined with hydrogen to produce ammonia. Although earth's atmosphere is 78% nitrogen gas, plants cannot utilize this nitrogen gas. Soil nitrogen must occur in a combined form with ammonia
Explain how plants can modify their structure and/or physiology to respond to either excessive light or low light conditions?
Plant cell can shift chloroplast towards or away from the light based on how much light is available, which will increase or decrease photosynthesis. Dermal (epidermis)- any of outer part of a plant (root, leaf, stem) ex: leaf that has it on top and bottom; it produces the cuticle--- cuticle is a waxy substance that prevents desiccation, UV damage, diseases, and herbivores Ground (cortex)- Parenchyma: food reserve, repair any damages, soft (leaves, flowers, and fruit), main tissue that's present in most plants, usually unspecialized except for a few like spongy and palisade Collenchyma: soft, less abundant than parenchyma tissue, alive at maturity, contribute to structure and flexibility, (if you have more collenchyma then more herbaceous plant like in tropical) Sclerenchyma: dead at maturity, used for strength and structure, typically have star-like structures Vascular tissue (vascular bundles)- supporting and protective tissue Xylem-tracheid (smaller, only in gymnosperms) and vessels (bigger) internal of ANY plant Phloem-food (sugars), sieve tubes (no nuclei), companion cells (has nuclei and a lot of ribosomes and mitochondria, power sieve tubes to function)
if a plant produces less expansins than normal, how is the growth of a plant affected? how is the growth of a plant affected if it produces more expansins than normal?
1. The plant wouldn't grow because there would be no expansion. 2. The cell wall is weakened therefore the plant would be weak and wouldn't grow normally/ healthily.
1. Are apical meristems important in vegetative growth? Explain how. 2. Are apical meristems important in reproductive growth? Explain how. 3. Are lateral meristems important in vegetative growth? Explain how. 4. Are lateral meristems important in reproductive development?
1. Yes they help in the growth of length of the plant 2. Yes, the stem growing taller allowing flowers to grown as well as fruits. 3. Yes, they promote the lateral growth of the stems helping with stability. Shoot Apical Meristems (SAM) are vital to vegetative growth because it produces tissues that make primary tissues and organs. Thus allowing it to grow in length. They grow in length by the activity of shoot and root apical meristems. They are equally as important for reproductive growth because the allow pollen, flowers, and fruit to grow. Both are known as primary meristems and primary growth. Lateral meristems (Secondary meristems) are important in vegetative growth by increasing the girth of woody stems and roots by producing secondary tissues. It is also more common in trees. However, itis not important nor does it control reproductive development. 4. NO. Apical is the reason it grows up and the auxin is why it grows up due to elongation. Lateral meristem is important in reproductive growth due to having buds and shots.
Explain how abscisic acid, brassinosteroids, and ethylene help plants cope with environmental stress.
Abscisic acid: helps plants cope with stress, slows and stops metabolism during environmental stress, induces buds and deed dormancy, prevents seed germination in unfavorable conditions and promotes stomatal closing Brassinosteroids: helps plants cope with stress, promote cell expansion, stimulate shoot elongation, prevents leaf drop, stimulate xylem development and promote stress responses thylene: promotes seedling growth, induces fruit ripening leaf and petal aging and drop, coordinates defenses against osmotic stress and pathogen attack
Lily placed a plant in her window and after a day or two, noticed that it had turned away from the room towards the window. She turned the plant, but after a few days, it had turned towards the window again. What hormone is involved and at the cellular level, how does it cause the plant to turn toward the window? What type of tropism is occurring?
Auxin is involved in this process, it is phototropism. Auxin goes to the shaded side causing growth on the shaded side pushing towards the light. Phototropism- a cellular perception of light and a growth response of stem tissue to an internal chemical signal. In this case, the plant senses light and responds by changing the location of the hormone auxin.Due to this the plant bends towards the light. AUXIN- INFLUENCE PLANT STRUCTURE, DEVELOPMENT, NX BEHAVIOR, FRUIT DEVELOPMENT
how does a plant establish its apical basal polarity? what hormones are important?
Auxin is the master hormone that is produced in the apical shoot tips. Results in the shoots growing up and the roots growing down
With respect to gravitropism, explain how auxin affects shoot growth and root growth differently.
Auxins establish apical-basal polarity of seed embryos; induces vascular tissue development Shoots grow upwards, auxin inhibit leaf and fruit drop and stimulate fruit development and mediate phototropism Roots grow downward, auxin promotes formation of adventitious roots
What are adaptations of some plants to obtain nutrients when they are lacking in the environment.
Carnivorous plants might consume something that has CO2 such as venus fly traps eating flies. Snow buttercup flowers use sun tracking to aim closer to the sun for light absorption and it increases reproductive fitness and it allows it to get energy.
Why do plants form symbiotic relationships with bacteria (e.g. cyanobacteria) and fungi (e.g. mycorrhizae)? What nutrients do they obtain from these relationships?
Cyanobacteria feeds off nutrients and obtains CO2 and water while the plants obtains Nitrogen from the cyanobacteria. Plants and bacteria: bacteria can provide the plant with more fixed nitrogen and the plants give bacteria organic nutrients Plants and fungi: Fungi can provide water and mineral nutrients and help plants obtain phosphate and the plants give fungi organic food from the roots; pale plants lose photosynthetic pigments and rely on organic compounds supplied by fungi.
Explain the synergistic (combined) effect of auxin, cytokinins, and gibberellins in plant growth.
Cytokinins induce cell growth, Auxin facilitate cell division and growth and gibberellins induce elongation. These three together help the plant grow.
Explain the synergistic (combined) effect of cytokinins, gibberellins, and ethylene in plant reproductive development.
Cytokinins: promote cell division, root growth, vascular tissue development, flower and seed production, aging, cytokinesis Gibberellins: stimulates cell division and elongation, stimulates stem elongation and flowering and promote seed germination Ethylene: promotes seedling growth, induces fruit ripening, leaf and petal aging and drop, coordinates defenses against osmotic stress and pathogen attack
why might desert plants have fewer guard cells or trichomes than tropical plants?
Desert plants might have fewer guard cells or trichomes than tropical plants because it closes the stomata to avoid from drying out.
Explain how auxin, ethylene, and brassinosteroids regulate cell expansion or elongation.
Ethylene has to do with fruit ripening, it can also get involved with the maturing of the plants involved with the bending of stems. Ethylenes restricts cell wall expansion. Auxin: plant hormone responsible for root development, "master" growth hormone, phototropism, prevent fruit drop, apical-basal polarity Ethylene: promotes seedling growth, induces fruit ripening leaf and petal aging and drop, coordinates defenses against osmotic stress and pathogen attack Brassinosteroids: helps plants cope with stress, promote cell expansion, stimulate shoot elongation, prevents leaf drop, stimulates xylem development and promote stress responses
how can you tell whether a plant is a eudicot or a monocot?
Eudicots: possess two seed leaves (woody trees, shrubs, vines, bean plants); eudicot flowers typically have petals and other parts numbering four, five, or a multiple of those numbers; stem vascular bundles are around the outside, arranged in a ring (important for secondary growth) Monocots: only one seed leaf (corn, tiny duckweed), monocot flower parts usually occur in threes or multiples of three; stem vascular bundles are scattered; secondary growth is absent
Explain why the abaxial (lower) and adaxial (upper) surfaces of a leaf are different in eudicots.
The adaxial surfaces (upper) are made up of parenchyma palisade tissue filled with chloroplasts while the abaxial tissues (lower) are made of spongy parenchyma tissues and stomata. The reason why the abaxial and adaxial surfaces of a leaf are different is due to the fact that the palisade parenchyma needs to be located under the epidermis in order to function photosynthesis and be more exposed to sunlight as well. The spongy parenchyma is on the abaxial side due to its closeness to the stomata and it's where gas exchange and water exchange occurs and its filled with chloroplasts. The stomata allow CO2 to enter when open and O2 to leave.
Explain the functional importance of dermal, ground, and vascular tissues in roots, stems, and leaves.
The dermis protects the plant and prevents desiccation (drying out) with the use of the stomata, trichomes, and wax only in leaves and stems. Ground tissues in the stems are the cortex which is made up of the parenchyma (stores starch) , sclerenchyma (strengthens and supports) , and collenchyma (flexibility). Roots, leaves, and stems
Design the optimal soil composition for a plant that requires aerated roots and a lot of nutrients. Please provide a justification for the percentages of type of soil constituents chosen. Also consider the importance of cation exchange.
Top soil, subsoil, solid base, bedrock....sand allows roots to grow however lets water through, clay traps water but is too dense for roots to grow, silt is nutrient rich and allows the plant to grow
If a stem is flexible, what is the most likely dominant tissue of that stem? If a stem is rigid, is the same tissue likely dominant?
cortex - collechyma is the part of the cortex that makes it flexible Flexible: collenchyma Rigid: sclerenchyma likely dominant
