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BIO Exam 2 - Stack 3
Plant Structure, Growth, and Responses
Question | Answer |
---|---|
___, ___, and ___ produce the plant body. | - growth - morphogenesis - cell differentiation |
___ link signal reception and response. | Signal transduction pathways |
Plant ___ help coordinate growth, development, and responses to stimuli. | hormones |
development | - the specific series of changes by which cells form tissues, organs, and organisms - requires growth, morphogenesis, and cell differentiation |
What factors affect development? | - genetic information - external environment |
A single genotype can produce different phenotypes in different environments. This is called ___. | developmental plasticity |
Explain the developmental plasticity of the aquatic plant Cabomba caroliniana. | - underwater leaves are feathery, which protects them from damage caused by moving water - surface leaves are pads that aid in flotation - both have genetically identical cells, but the different environments turn off/on different genes |
growth | an irreversible increase in size |
morphogenesis | - morph=shape, genesis=creation - the process that gives a tissue, organ, or organism its shape - also determines the positions of cell types |
cell differentiation | - the process by which cells with the same genes become different from one another - change in what the cells are like from one another |
The ___ refers to development of the new cell wall that bisects a plant cell during cytokinesis. | plane of cell division |
cytokinesis | the division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II |
What is transverse division and what does it lead to in leaf growth? | - the plane is crosswise - associated with leaf elongation (length) |
What is longitudinal division and what does it lead to in leaf growth? | - the plane is vertical - associated with leaf broadening (width) |
Do mutations that affect the plane of cell division (e.g., tangled-1) affect leaf shape? | no (only appear different when looked at under microscope) |
Although the plane of cell division does not determine the shape of plant organs, the ___ of cell division is important in determining cell fate. | symmetry |
What do we mean by symmetry of cell division? | - whether or not plant cells divide into two equal halves during mitosis - cytoplasm can be distributed unevenly |
What is asymmetrical cell division and what does it signal? | - when one daughter cell receives more cytoplasm than the other during mitosis - usually signals a key event in development (differentiation) |
What do guard cells have to do with asymmetrical cell division? | - an asymmetrical cell division precedes the development of epidermal guard cells (cells that border stomata) - unspecialized epidermal cell --asymmetrical cell division-->unspecialized epidermal cell+guard cell (less cytoplasm) |
Asymmetrical cell division also plays a role in establishment of ___. | polarity |
polarity | the condition of having structural or chemical differences at opposite ends of an organism |
What is the first cell division of a plant zygote like? What does the establishment of polarity lead to in plants? | the first division of a plant zygote is normally asymmetrical, initiating polarization of the plant body into shoot and root |
What happens if the first cell division of a plant zygote is symmetrical instead (e.g., the gnom mutant)? | - establishment of polarity is defective - the first cell division of the zygote is abnormal because it is symmetrical - the resulting ball-shaped plant has neither roots nor shoots - the plant dies |
Growing plant cells expand mainly through ___ and ___. | - water uptake - “packaging” of water in the large central vacuole of the cells |
What is the usual orientation of cell growth and how is that determined? | - plant cells' expansion usually oriented along the plant's main axis - (so lengthwise...cells expanding vertically) |
cellulose microfibrils | - the main structure of plant cell walls made of cellulose - these strands do not stretch, so plant cells expand perpendicular to the orientation of the microfibrils |
During morphogenesis, cells acquire different identities in an ordered spatial arrangement. What does that mean? | the position of a cell has a lot to do with what it is going to become |
pattern formation | - the development of specific structures in specific locations - ex. humans have 2 ears on the sides of their heads |
Experimental work has shown that a plant cell’s fate is established ___ in development and largely depends on ___. | - late - signaling from neighboring cells |
Given that the cells of a developing organism share a common genome, what controls differentiation? | cell differentiation depends on the control of gene expression (the regulation of transcription and translation, resulting in the production of specific proteins) |
Although cell differentiation depends on the control of gene expression, the fate of a plant cell is determined by ___. | its final position in the developing organ |
___ is communicated from one cell to another. | Positional information |
phase changes | - the morphological changes that arise from the transitions in shoot apical meristems - (unlike animals, plant developmental stages [phases] occur within a single region, the shoot apical meristem) |
What does dual foliage show? | - juvenile vs adult phase of apical meristem - it reflects a phase change in the development of the apical meristem of each shoot |
Flower function involves a phase change from ___ growth to ___ growth. | - vegetative - reproductive |
This phase change involves the conversion of ___ vegetative meristems to ___ floral meristems and is associated with the switching on of floral ___. | - indeterminant - determinant - meristem identity genes |
meristem identity gene | - a plant gene that promotes the switch from vegetative growth to flowering - controls whether meristem a branch or floral |
What are the four main floral organs? | - sepals - petals - stamens - carpels |
How are floral organs arranged? | - the floral parts form 4 whorls that can be roughly described as concentric circles when viewed from above - sepals form the first (outermost) whorl, petals the second, stamens the third, and then carpels form the first (innermost whorl) |
What are organ identity genes, what do they control, and how do they control it? | plant homeotic genes that use positional information to determine which emerging leaves develop into which types of floral organs |
homeotic gene | genes that control the placement and production of parts in the body plan of an organism |
A ___ in a plant organ identity gene can cause abnormal floral development, such as petals growing in place of stamens. | mutation |
By studying mutants with abnormal flowers, researchers have identified three classes of floral identity genes: | A, B, and C |
What genes code for what floral organs? (Remember the memorization sentence!) | - A gene activity codes for sepals - A+B gene activity codes for petals - B+C gene activity codes for stamens - C gene activity codes for carpels - (“It's as easy as ABC in Sepe Street, California!”) |
In the ABC hypothesis, what happens if A is missing? If C is missing? | - if A is missing, C takes its place (carpels grow) - if C is missing, A takes its place (sepals grow) |
Animals, being mobile, respond to stimuli mainly by moving toward positive stimuli and away from negative stimuli. What about plants? | - plants, being stationary, generally respond to environmental cues by adjusting their individual patterns of growth and development...or - plants receive specific signals and respond to them in ways that enhance survival and reproductive success |
___ link signal reception to response. | Signal transduction pathways |
The de-etiolation (greening) of dark-grown potatoes are an example of: | how a plant cell's reception of a signal (in this case light) is transduced into a response (greening) |
In the de-etiolation of potatoes, the light signal is detected by the ___. | phytochrome receptor |
What initiates a de-etiolation response? | - post-translational modification of preexisting proteins - transcriptional regulation |
What is post-translational modification of preexisting proteins? When did it actually happen? | - activation of preexisting enzymes - happens during transduction stage - second messengers are made that activates protein kinases |
What is transcriptional regulation and where is it happening? | - genes transcribed in the nucleus - transcription factors phosphorylated by kinases, they bind to DNA, it turns genes on |
What are de-etiolation response proteins and what do you think they’re doing? | - enzymes that function in photosynthesis directly - had to be turned on (stimulated by light) |
Plant ___ help coordinate growth, development, and responses to stimuli. | hormones |
hormone | - a signaling molecule that is produced in tiny amounts by one part of an organisms body and transported to another part - transported through plants and activate signal transduction pathways that greatly alter the functioning of plants |
tropism | - tropos=turn - any growth response that results in plant organs curving (turning) toward or away from stimuli |
phototropism | - the growth of a shoot toward or away from light - positive phototropism = toward light, negative = away |
In 1880, ___ removed and covered parts of grass coleoptiles to determine what part senses light. (Coleoptile is the covering of the young shoot of the embryo of a grass seed.) | Charles and Francis Darwin |
___ separated coleoptiles with different materials to determine how the signal for phototropism is transmitted. (Coleoptile is the covering of the young shoot of the embryo of a grass seed.) | Peter Boyce-Jensen |
What conclusion did Charles and Francis Darwin make about coleoptiles? | - only the tip of the coleoptile senses light - the phototropic bending occurred at a distance from the site of light perception (the tip) |
What conclusion did Peter Boyce-Jensen make about coleoptiles? | the signal for the bending is a light-activated mobile chemical |
What conclusion did Frits Wents make about coleoptiles? | - a coleoptile curves toward light because its dark side has a higher concentration of the growth-promoting chemical - (the chemical causes cells to elongate) |
Plant growth, development, and responses to stimuli are highly coordinated and under control of multiple chemical agents known as: | hormones (or plant growth regulators) |