bio 2 exam 2 hw
how and when does CO2 get into CAM leaves?
at night when it is cool and stomata are open
petals
attract the attention of pollinators
. What stages of the life cycle are eliminated or bypassed when plants are cloned naturally? When plants are cloned on the farm or in the laboratory?
gametophyte generation.
Which enzyme(s) (1) capture carbon dioxide and (2) carry it to the Calvin cycle in C3 plants?
picked up by rubisco and catalyseze for step in calvin cycle
Fertilizer generally contains nitrogen and phosphorus compounds required by plants. The nitrogen is often in the form of nitrates, and the phosphorus is in the form of phosphates. Based on what you know about chemistry and water potential, why would overfertilizing lead to the death of plants?
Adding nitrates and phosphates to the soil will decrease the water potential in the soil. If the water potential in the soil equals the water potential in the root or is less than that in the root, water will not flow into the root (when potentials are equal) and will actually leave the root (when the water potential in the soil is lower than it is in the root).
herbaceous dicot and woody dicot apical meristem shoot vs root
As in monocots, the apical meristems of the roots are generally protected by a root cap. There is gener-ally no protec-tive tissue layer over the apical meristems of the aerial portions of the plant.
What does the science of plant biotechnology do that artificial selection and/or cloning practices don't do?
Biotechnology can add genes from other organisms to plants. For example, a gene from Bacillus thuringiensis has been added to some crop plants. It produces the Bt toxin, which acts as an insecticide.
double fertilization
Fertilization occurs when a sperm nucleus from the pollen tube joins with the egg nucleus in the embryo sac. In double fertilization, the other sperm nucleus (from the pollen tube) joins with the polar nuclei to form the endosperm nucleus.
The metabolic pathways of organisms living today evolved over a long period of time— undoubtedly in a stepwise fashion because of their complexity. Put the following processes in the order in which they might have evolved, and give a short explanation for your arrangement. Krebs Cycle Electron transport glycolysis photosynthesis
First, glycolysis is found in all eukaryotes and many prokaryotes. It takes place in the cytoplasm and can occur in the absence of oxygen. Second, photosynthesis produces oxygen as a by-product. Neither the Krebs cycle nor electron transport can occur in the absence of oxygen. Third, electron transport is required to convert NADH to NAD+ . Because glycolysis produces 2 ATP (net) and 2 NADH, the addition of electron transport represents an advantage. Organisms can then gain 8 ATP (net) from glycolysis plus electron transport. Fourth, the Krebs cycle cannot occur without a mechanism to convert NADH to NAD+ . Electron transport must have evolved before the Krebs cycle.
monocot apical meristem shoot vs root
apical meristem is covered by a root cap. have intercalary meristems. ex: grass
What design modifications would you need to make to support plants with different photoperiods—for example, long-day versus short-day plants?
If the different plant species you were growing had different photo-periods, you would need to growth them in separate cham-bers. You could then set up different timer controls in each chamber to regulate the number of hours of light (versus dark) per day (24 hours).
A cartoon shows a man going to sleep in a hammock suspended between two relatively short trees. The second frame of the cartoon shows the man waking 20 years later and finding his hammock 15 feet higher off the ground. Critique this drawing in terms of what you know about the growth pattern of trees.
If the tree is a dicot, then its growth in height occurs by the addition of cells at the apical meristems. As a result, the position of the hammock should not change over time.
How does the water potential in the air compare to that in the leaf of a plant undergoing transpiration?
If transpiration is occurring, the air must have a lower water potential than the leaf.
What light characteristics would you use to maximize plant growth per unit time?
In photosynthesis, the chlorophyll molecules in photo-systems I and II respond to or absorb light in the red and blue wavelengths of the visible spectrum. As a result, if nothing else is limiting, the more red and blue light available, the faster the photosynthetic rate per unit time
What kind of physical environment would you need to maintain appropriate phototropic responses among plants?
In space or in the lab, you would need to set up banks of overhead lights. Light bulbs that are rich in red and blue wavelengths should be used. A hydroponic growth system should be set up to include a meshwork mat to support seeds or seedlings in early growth and to sup-port the stems and maintain the roots below the mat (in the hydroponic solution) in later growth
If cross sections were not available, what other characteristics of the plants as a whole could you use to determine whether each was a monocot, a herbaceous dicot, or a woody dicot?
Monocot leaves have parallel veins (vascular bundles); dicot leaves have netlike veins. Monocot floral parts are generally in multiples of three; dicot floral parts are in multiples of four or five. Monocots tend to have fibrous root systems; dicots usually have taproot systems. Older woody dicots could obviously be distinguished from herbaceous dicots by the presence of woody lateral growth, including bark. Very young woody dicots would be difficult to distinguish from herbaceous dicots.
How would a lack of gravity affect normal growth?
Normal seed germination and seedling growth begin underground in the absence of light. Under these conditions, the seedling relies on the gravitropic responses of the shoot and root to orient these above ground and underground, respectively. In the absence of gravity, auxin concentrations in the root and shoot would not vary, and growth of the shoot away from gravity and growth of the root toward gravity would not occur.
If overwatering kills plants, why can you sprout roots from cuttings of stems in water?
Oxygen from the atmosphere can diffuse into the water in a jar or vase. As a result, the water will contain enough oxygen to allow cellular respiration to continue in the roots. (If the jar is clear and in the sun, green portions of the root underwater will also photosynthesize and add additional oxygen to the water.) However, air spaces in soil are narrow and penetrate deep into the soil. When these are filled with water, the surface area available for the diffusion of oxygen into the water is greatly reduced.
Which enzyme(s) (1) capture carbon dioxide and (2) carry it to the Calvin cycle in C4 plants?
PEP carboxylase in the mesophyll cells converts CO2 to a four-carbon organic acid, which is transported to the bundle sheath cells, where it is converted to CO2 and PEP, and rubisco catalyzes the first step in the Calvin cycle.
Which enzyme(s) (1) capture carbon dioxide and (2) carry it to the Calvin cycle in CAM plants?
PEP carboxylase in the mesophyll cells converts CO2 to a four-carbon organic acid, which is transported to the cells' central vacuoles and can later be converted back to CO2 and PEP. The CO2 can then be picked up by rubisco and used in the Calvin cycle in mesophyll cells.
what makes C4 photosyntheissi more efficient than C3 in tropical climates
PEP carboxylase is more effiecnet at picking up CO2 so C4 plants get more CO2 and store it for later which means that during hot times the stomata can close and still continue with the calvin cycle by using that stored CO2. high CO2 to O2 ration
Xylem cells are dead when functional. Why must phloem cells be alive when functional?
Phloem cells must be capable of loading sugars against a concentration gradient. To do this, they must have a semipermeable membrane and must expend ATP. As a result, they must be alive.
Why could we call photorespiration a "mistake" in the functioning of the cell?
Photorespiration could be called a "mistake" because under high O2/CO2 conditions, rubisco breaks down glucose into carbon dioxide and water but no useful energy is gained.
Propose mechanisms to overcome the problems associated with a lack of gravity.
Plant orientation is also affected by light. (See question 2.) The response to light can help counteract the lack of gravity. In addition, if plants are grown hydroponically, a dense meshwork mat can be used to prevent roots from growing above water.
One of the most common ways of killing a plant is overwatering. Why does overwatering kill a plant?
Roots, like all other living tissues of the plant, require oxygen for cellular respiration. If you overwater a plant, you fill all the air spaces in the soil with water. Root tissue cannot survive without oxygen.
If water flows from a region of more positive (higher) water potential to a region of more negative (lower) water potential, how does the water potential in the root compare to that in the soil outside the root?
The water potential in the soil must be higher than it is in the root.
How does gravity affect the normal growth of a plant's roots, stems, and other parts? Explain the mechanisms involved.
Under the influence of gravity, auxin accumulates on the lower side of the root and stem. Higher auxin concentrations stimulate cell elongation in the stem but inhibit cell elongation in the root. In the shoot region, a concentration of auxin between 10-8 and 10-4 stimulates cell elongation. According to the acid growth hypothesis, auxin concentrations in this range stimulate proton pumps, which lower the pH in the cell wall. This activates enzymes that break crosslinks between cellulose molecules and allow the cell to elongate.
How do water's properties of adhesion and cohesion help maintain the flow of water in the xylem of a plant?
Water molecules cohere to one another and adhere to the sides of the xylem vessels or tracheids. As negative pressure is applied to pull the water up in the xylem, each water molecule therefore pulls on the next in the column. As a result, the entire water column rises.
Rubisco is thought to have evolved when Earth had a reducing atmosphere. How does this help explain the photorespiration "mistake?"
When the first photosynthetic organisms arose, the early Earth's atmosphere contained little, if any, oxygen. Rubisco would have functioned very well under these conditions. It was only later, when the concentration of oxygen in the atmosphere increased considerably, that rubisco's ability to oxidize glucose became evident.
carpel
contain the femal megasporangium
anther
contain the male microsporangium
how and when does CO2 get into C4 leaves?
during cooler parts of the day when stomata are open
how and when does CO2 get into C3 leaves?
during the day when the stomata are open
sepals
enclose and protect the developing flower
photoperiodism
is a physiological response to changes in day length. For example, the physi-ological responses that cause flowering in some species of plants are triggered by changes in day length.
phototropism`
is the growth of a plant toward or away from light. In general, shoots grow toward light (are positively photo-tropic) and roots grow away from light (are negatively phototropic). Again, this response appears to be the result of assymetric distribution of auxin.
what is included in a mature ovule?
micropyle integuments-2 nucellus synergids-2 polar nuclei-2 egg-1 anti-podals cells-3
what causes xylem conduction?
negative partial pressure generated in the xylem. Transpirational loss of water at the leaf surface (and elsewhere) on the plant generates this negative partial pressure.
herbaceous dicot root
no central pith. xylem forms crosslike pattern in the center of the root. phloem sits in the arms of the cross.
microsporeogenesis
occurs in the sporangia of the anther in flowers. Microsporocytes (2n) undergo meiosis to produce haploid microspores; each then develops into a pollen grain
megasporogenesis
occurs in the sporanium of the ovule in flowers. The megasporocyte (2n) undergoes meiosis to form a haploid megaspore (plus three other haploid cells that do not survive). The megaspore undergoes mitosis to produce the embryo sac, which contains the egg, synergids, antipodal cells, and polar nuclei.
pollination
occurs when pollen lands on the stigma of a genetically compatible plant.
what force causes phloem conduction
positive hydrostatic pressure in cells. generated by the difference in water potential in phloem versus xylem. Sucrose is actively transported into phloem (to levels as high as 25%). This potential difference pulls water out of the xylem and into the phloem, generating the hydrostatic pressure that moves substances in phloem
woody dicot root
ring of vascular cambium forms between the central xylem and phloem and lays down 2ndary zylem and phloem
what is part of a complete flower?
sepals, petals, stamens, and carpels
How is CAM photosynthesis advantageous in desert climates
stomata opens at night and the PEP carboxylase allows desert plants to store CO2. however, the amount that can be stored in the central vacule of cells is finite
woody dicot stem
vascular CAMBIUM is continous and produces xylem and phloem to the outside. depending on water availability can result in growth rings
monocot root
vascular bundels are in a ring pattern around the central pith
monocot stem
vascular bundels are scattered
herbaceous dicot stem
vascular bundles are arranged in a ring between a thin outer cortex later and a central pitth
herbaceous/woody dicott leaf
veins are in netlike pattern. vascular bundles are not spaced evenly and are different sizes
monocot leaf
veins are parallel. vascular bundles are evenly spaced and are the same size