Plant Biology - GRE Subject Test: Biology
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Double fertilization in angiosperms results in a __________ zygote and a triploid __________.
Double fertilization in angiosperms results in a __________ zygote and a triploid __________.
Double fertilization is the process by which two sperm cells are introduced to the ovule. One sperm (
) fertilizes the egg (
), creating a zygote(
). The other sperm combines with the two polar nuclei (
), forming the endosperm (
) that will nourish the embryo.
Double fertilization is the process by which two sperm cells are introduced to the ovule. One sperm (
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Which of the following is not true of auxins, a class of plant hormones?
Which of the following is not true of auxins, a class of plant hormones?
Auxins play a number of crucial roles in plant growth, behavior, and development. They were the first major class of plant hormone to be discovered and are present in all parts of a plant in varying concentrations. Some of their more notable functions include causing phototropism, enhancing apical dominance, and softening the cell wall to stimulate cell elongation and growth. Indoleacetic acid (IAA) is a naturally occurring auxin, though some synthetic auxins are used as weed killers.
Ethylene gas is a plant hormone that promotes fruit ripening in a positive feedback loop. Ripe fruit produces more ethylene gas, which promotes more fruit ripening, and so on. It is not a kind of auxin.
Auxins play a number of crucial roles in plant growth, behavior, and development. They were the first major class of plant hormone to be discovered and are present in all parts of a plant in varying concentrations. Some of their more notable functions include causing phototropism, enhancing apical dominance, and softening the cell wall to stimulate cell elongation and growth. Indoleacetic acid (IAA) is a naturally occurring auxin, though some synthetic auxins are used as weed killers.
Ethylene gas is a plant hormone that promotes fruit ripening in a positive feedback loop. Ripe fruit produces more ethylene gas, which promotes more fruit ripening, and so on. It is not a kind of auxin.
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Perishable fruit is often picked before it is ripe. This hard, unripe fruit is easier to transport as it is less likely to bruise or spoil while in transit. Once fruit reaches its destination, it can be sprayed with a plant hormone that will promote its rapid ripening. What hormone is most likely used for this function?
Perishable fruit is often picked before it is ripe. This hard, unripe fruit is easier to transport as it is less likely to bruise or spoil while in transit. Once fruit reaches its destination, it can be sprayed with a plant hormone that will promote its rapid ripening. What hormone is most likely used for this function?
Ethylene gas promotes fruit ripening; in a classic example of a positive feedback loop, ripe fruit causes the production of more ethylene gas, which promotes more fruit ripening (this is the origin of the phrase "one bad apple spoils the bunch!")
Cytokinins stimulate cell division and cytokinesis, and they can delay senescence (deterioration due to age, as in the case of cells). Gibberellins promote cell growth, and also promote stem and leaf elongation. Abscisic acid (ABA) promotes seed dormancy, inhibits plant growth, and closes plant stomata during water shortages.
Ethylene gas promotes fruit ripening; in a classic example of a positive feedback loop, ripe fruit causes the production of more ethylene gas, which promotes more fruit ripening (this is the origin of the phrase "one bad apple spoils the bunch!")
Cytokinins stimulate cell division and cytokinesis, and they can delay senescence (deterioration due to age, as in the case of cells). Gibberellins promote cell growth, and also promote stem and leaf elongation. Abscisic acid (ABA) promotes seed dormancy, inhibits plant growth, and closes plant stomata during water shortages.
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Indole-3-acetic acid (IAA) is the most abundant hormone in plants. IAA falls under which classification of plant hormone?
Indole-3-acetic acid (IAA) is the most abundant hormone in plants. IAA falls under which classification of plant hormone?
The correct answer is auxin. IAA is the most abundant auxin naturally found in plants, and plays key roles in plant development and growth.
The correct answer is auxin. IAA is the most abundant auxin naturally found in plants, and plays key roles in plant development and growth.
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What structure in plants allows for CO2 and O2 exchange and transpiration?
What structure in plants allows for CO2 and O2 exchange and transpiration?
The stoma allows for gas exchange and transpiration. The stoma usually opens following stimulation by sunlight and closes in low water environments. Other answers are parts of a typical plant, however do not play a role in gas exchange or transpiration.
The stoma allows for gas exchange and transpiration. The stoma usually opens following stimulation by sunlight and closes in low water environments. Other answers are parts of a typical plant, however do not play a role in gas exchange or transpiration.
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Which plant tissue system is similar to the human circulatory system?
Which plant tissue system is similar to the human circulatory system?
A plant's vascular tissues transport nutrients throughout the plant, just as the circulatory system transports nutrients throughout human bodies. While blood is the primary solvent for nutrients in humans, water is the primary solvent for nutrients in plants. Animals, however, use blood pressure to propel nutrients throughout the body while plants use gravity and the cohesive properties of water to transport nutrients.
The two primary types of plant vascular tissue are xylem, which transports water, and phloem, which transports organic molecules like glucose.
A plant's vascular tissues transport nutrients throughout the plant, just as the circulatory system transports nutrients throughout human bodies. While blood is the primary solvent for nutrients in humans, water is the primary solvent for nutrients in plants. Animals, however, use blood pressure to propel nutrients throughout the body while plants use gravity and the cohesive properties of water to transport nutrients.
The two primary types of plant vascular tissue are xylem, which transports water, and phloem, which transports organic molecules like glucose.
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Of the following answer choices, which most accurately describes the mechanism that the stems of plants use to grow toward light?
Of the following answer choices, which most accurately describes the mechanism that the stems of plants use to grow toward light?
Plants grow so as to maximize the elongation of their stems as much as possible. Cells on the lighter side of the stem are already being provided with photosynthetic energy, while cells on the darker side are receiving less of this energy input. This causes the cells on the darker side to elongate toward the energy source. When one side of the stem is longer than the other, it causes a curve in the growth, resulting in a directionality of the growth of the stem.
Plants grow so as to maximize the elongation of their stems as much as possible. Cells on the lighter side of the stem are already being provided with photosynthetic energy, while cells on the darker side are receiving less of this energy input. This causes the cells on the darker side to elongate toward the energy source. When one side of the stem is longer than the other, it causes a curve in the growth, resulting in a directionality of the growth of the stem.
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What is the function of lateral meristems?
What is the function of lateral meristems?
In addition to growing in height, woody plants also grow in thickness. This is the function of lateral meristems. Lateral meristems are comprised of the vascular cambrium, and by cork cambrium that form vascular cylinders. The vascular cambrium adds layers of secondary xylem and phloem (wood), whereas the cork cambrium replaces the outer epidermis with a thicker and tougher layer called periderm.
In addition to growing in height, woody plants also grow in thickness. This is the function of lateral meristems. Lateral meristems are comprised of the vascular cambrium, and by cork cambrium that form vascular cylinders. The vascular cambrium adds layers of secondary xylem and phloem (wood), whereas the cork cambrium replaces the outer epidermis with a thicker and tougher layer called periderm.
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Which of the following is a key component of a plant's vascular system?
Which of the following is a key component of a plant's vascular system?
The vascular system in plants is designed to transport materials (water, nutrients, food) between the roots and shoots. There are two primary types of tissue dedicated to these processes. Xylem transports water and dissolved minerals upward from the roots; phloem transports sugars—the products of photosynthesis—from where they are synthesized to where they are needed, such as roots and new growth areas of leaves and fruits.
Both xylem and phloem are comprised of a variety of cell types that are specialized for transport and support.
The vascular system in plants is designed to transport materials (water, nutrients, food) between the roots and shoots. There are two primary types of tissue dedicated to these processes. Xylem transports water and dissolved minerals upward from the roots; phloem transports sugars—the products of photosynthesis—from where they are synthesized to where they are needed, such as roots and new growth areas of leaves and fruits.
Both xylem and phloem are comprised of a variety of cell types that are specialized for transport and support.
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Plant root systems can be generally categorized as either taproot systems or fibrous root systems. Which of the following is a characteristic of a fibrous root system?
Plant root systems can be generally categorized as either taproot systems or fibrous root systems. Which of the following is a characteristic of a fibrous root system?
Fibrous root systems are common in seedless vascular plants and in most monocots, such as grasses. Many small roots grow from the stem of the plant and are considered adventitious (a term describing a plant organ that grows in an unusual location).
Fibrous roots have no main root and do not penetrate deeply into the soil, usually penetrating only a few centimeters. As such, fibrous root systems are best adapted to shallow soil. This also helps prevent erosion, as the shallow, highly-branched roots hold the topsoil in place.
Fibrous root systems are common in seedless vascular plants and in most monocots, such as grasses. Many small roots grow from the stem of the plant and are considered adventitious (a term describing a plant organ that grows in an unusual location).
Fibrous roots have no main root and do not penetrate deeply into the soil, usually penetrating only a few centimeters. As such, fibrous root systems are best adapted to shallow soil. This also helps prevent erosion, as the shallow, highly-branched roots hold the topsoil in place.
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Which of the following is a type of stem?
Which of the following is a type of stem?
Stems are one of the three basic plant organs, and consist of an alternating system of nodes (where leaves attach) and internodes (regions of the stem that span between nodes).
Some plants have evolved to have stems with additional functions, such as the ability to store food or to participate in asexual reproduction. These modified stems include rhizomes, bulbs, tubers and stolons.
A rhizome is a horizontal shoot of the plant that grows just below the surface. Vertical shoots (and resulting leaves) grow from axillary buds on the rhizome. Examples of plants with rhizomes include irises, hops, and asparagus.
Stems are one of the three basic plant organs, and consist of an alternating system of nodes (where leaves attach) and internodes (regions of the stem that span between nodes).
Some plants have evolved to have stems with additional functions, such as the ability to store food or to participate in asexual reproduction. These modified stems include rhizomes, bulbs, tubers and stolons.
A rhizome is a horizontal shoot of the plant that grows just below the surface. Vertical shoots (and resulting leaves) grow from axillary buds on the rhizome. Examples of plants with rhizomes include irises, hops, and asparagus.
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Which of the following is false?
Which of the following is false?
Xylem is dead at maturity, while phloem is living. All other answer choices are true. Xylem is also thicker and more rigid, which allows for greater pressure during water transport. It provides a strong support structure for the plant, enabling taller growth.
Xylem is dead at maturity, while phloem is living. All other answer choices are true. Xylem is also thicker and more rigid, which allows for greater pressure during water transport. It provides a strong support structure for the plant, enabling taller growth.
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What is the tissue found in many vascular plants which forms as part of the periderm and generates secondary growth in roots and stems?
What is the tissue found in many vascular plants which forms as part of the periderm and generates secondary growth in roots and stems?
The periderm forms a protective layer around the outside of many stems and roots and consists of cork cambium, cork, and phelloderm. Cork cambium is the site of active secondary growth within the periderm of vascular plants. Phloem is a type of vascular tissue that directs the flow of nutrients and metabolic products from the leaves down to the roots.
The periderm forms a protective layer around the outside of many stems and roots and consists of cork cambium, cork, and phelloderm. Cork cambium is the site of active secondary growth within the periderm of vascular plants. Phloem is a type of vascular tissue that directs the flow of nutrients and metabolic products from the leaves down to the roots.
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Which of the following structures is unique to plant cells?
Which of the following structures is unique to plant cells?
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
Chloroplasts are organelles in plant cells that conduct photosynthesis; therefore they are unique to plant cells. All the other mentioned organelles can be found in both animal and plant cells.
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Which of the following can be found in plant cells, but not animal cells?
Which of the following can be found in plant cells, but not animal cells?
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
Chloroplasts, the site of photosynthesis, are only in plant cells and are not found in animal cells. Ribosomes, a cell membrane, and a mitochondria, however, can be found in both animal and plant cells.
The other structure that may be found in plant cells, but not animal cells, is a cell wall.
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The Calvin cycle takes place in the __________ and occurs __________.
The Calvin cycle takes place in the __________ and occurs __________.
The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur.
The Calvin cycle takes place in the stroma of the chloroplast, which is the region in the chloroplast lumen outside of the thylakoids. It does not actually matter whether or not light is present for the reactions of the Calvin cycle to take place. They are light independent, but light will not prevent the reactions from occurring, similar to how glycolysis is independent of oxygen. As long as the appropriate nutrients and reactants are present, including ATP and NADPH generated from the light reactions, the Calvin cycle will occur.
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Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?
Where in the chloroplasts does the Calvin Cycle of photosynthesis take place?
The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.
The Calvin Cycle occurs in the stroma, the aqueous fluid-filled area of the chloroplast. The stroma can be seen as analogous to the cytoplasm of a cell, in that it is the liquid in which all other substructures reside. The other processes of photosynthesis, the light-dependent reactions, take place in the thylakoid, a membrane-bound substructure within the chloroplast.
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What is the purpose of photosystem II in photosynthesis?
What is the purpose of photosystem II in photosynthesis?
Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi.
Photosystem II splits water into hydrogen and oxygen. Hydrogen ions accumulate in the thylakoid space, creating an electrochemical concentration gradient. Due to this gradient, hydrogen ions pass through ATP sythase, powering the synthesis of ATP from ADP + Pi.
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In plants, leaves contain specialized pores used for gas exchange. Each pore is formed by a pair of cells that control its closing and opening. What are these cells called?
In plants, leaves contain specialized pores used for gas exchange. Each pore is formed by a pair of cells that control its closing and opening. What are these cells called?
For proper functioning, plants must take in carbon dioxide, expel oxygen, and limit the loss of water vapor. This gas exchange takes place via pores called stomata. These pores are formed by a pair of adjacent cells that can open and close in response to a number of factors. These cells are called guard cells.
The cuticle and epidermis are layers of leaf structure, and do not correspond to specific cell types. The stoma is the name of a single pore itself, not its surrounding cells.
For proper functioning, plants must take in carbon dioxide, expel oxygen, and limit the loss of water vapor. This gas exchange takes place via pores called stomata. These pores are formed by a pair of adjacent cells that can open and close in response to a number of factors. These cells are called guard cells.
The cuticle and epidermis are layers of leaf structure, and do not correspond to specific cell types. The stoma is the name of a single pore itself, not its surrounding cells.
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Plant cells differentiate to perform different functions and enable the plant to grow. One cell type is present in young stems and petioles and functions to provide flexible support. This cell type is less resistant to bending forces because it lacks a secondary cell wall and the protein lignin, which causes rigidity in other plant cells.
What differentiated plant cell is being described?
Plant cells differentiate to perform different functions and enable the plant to grow. One cell type is present in young stems and petioles and functions to provide flexible support. This cell type is less resistant to bending forces because it lacks a secondary cell wall and the protein lignin, which causes rigidity in other plant cells.
What differentiated plant cell is being described?
As described in the beginning of this question, collenchyma cells are found in young stems and petioles (leaves) and function to provide flexible support to the plant. This is because chollenchyma cells lack secondary cell walls and do not produce lignin to harden them—this protein is characteristic of sclerenchyma cells, which are also used to provide support/strength to the plant.
Due to their lack of rigidity, collenchyma cells a also capable of elongating with the stems and leaves they support, allowing them to remain alive at maturity. Sclerenchymal cells lack this ability.
As described in the beginning of this question, collenchyma cells are found in young stems and petioles (leaves) and function to provide flexible support to the plant. This is because chollenchyma cells lack secondary cell walls and do not produce lignin to harden them—this protein is characteristic of sclerenchyma cells, which are also used to provide support/strength to the plant.
Due to their lack of rigidity, collenchyma cells a also capable of elongating with the stems and leaves they support, allowing them to remain alive at maturity. Sclerenchymal cells lack this ability.
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