Plant Functions - AP Biology

In hypothesis-based scientific inquiry, the experiment must have an experimental group and a control group. In this case, growing plants with potassium would be the experimental group and growing plants without potassium would be the control group. Maintaining all other experimental variables, this method would allow the researcher to determine whether the plant species requires potassium. If the plants in the potassium-deprived environment die, but the plants in the potassium-rich environment survive, we can conclude that potassium is necessary for this species to survive.

The presence of potassium in the plant, leaves, or roots does not indicate it is a required nutrient. This simply indicates that the plant is capable of absorbing potassium, but does not show a dependency on potassium. Also, the movement of potassium into the plant does not indicate it is a required nutrient.

There are many necessary nutrients involved in plant development. The nutrients are used in different quantities and are grouped accordingly in two categories: micronutrients and macronutrients. Micronutrients, such as iron, are important to healthy plant growth but are used in small quantities. Macronutrients, such as oxygen, carbon, hydrogen, and phosphorus, are also used for healthy plant growth but are used in the greatest quantities.

As a result, the macronutrients are more likely to become depleted in the soil as the plant absorbs them, while the micronutrients remain abundant. Iron, as a micronutrient, is more likely to be abundant in soil than any of the macronutrients.

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.

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.

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.

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.

The sporophyte produces spores, which grow into gametophytes. The gametophyte produces both ovules and pollen, which unite to form a zygote. The zygote grows into the next sporophyte. The plant life cycle continues to alternate between these stages. In flowering plants, the gametophyte stage has been greatly reduced compared to the sporophyte stage.

Pollination is the process in angiosperms through which pollen is transferred from the male anther to the female stigma. Pollination can be either abiotic (i.e. by the wind) or biotic (i.e. by an animal). This process precedes fertilization.

Pollination is defined as the transfer of pollen from the male anther to the female stigma of an angiosperm. There are abiotic and biotic methods of pollinations. Abiotic pollination includes wind and water while in biotic pollination another organism facilitates pollination.

Pollen is the male part of the plant, and thus is only produced by male ginkgo plants. Females have ovules with a fleshy, fruit-like outer layer and rely on the males plants for pollination. (Ginkgo is a gymnosperm and thus technically not a flowering/fruit-producing plant.)

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.

Plants do not have the ability to actively transport water to their respective cells. Instead, water undergoes capillary action, which allows it to flow upward against gravity. When the water is located in a very narrow chamber, such as the xylem of a plant, it creates intermolecular interactions with the walls of the chamber. These interactions allow small amounts of the water to "climb" the chamber walls. Due to the cohesion of water, whereby it is attracted to itself, more water molecules follow the "climbing" adhesion molecules. This subsequently allows the adhering molecules to climb higher, and the joint interaction of the adhesion and cohesion eventually allow the water to reach the topmost region of the plant (the leaves). Water is then released from the stomata, furthering the pull of water to the region of low pressure.

One of water's most distinctive properties is cohesion—that is, the tendency of water molecules to "stick" to one another. In plants, this cohesion results in columns of water that stretch through the plant's xylem (the vascular tissue responsible for transport of water), from the roots all the way to the leaves. During transpiration, water evaporates from plants' leaves. Because of the cohesion of water, whenever water evaporates, more molecules are "pulled" into the roots to maintain the column of water. This is the transpirational pull-cohesion tension theory.

In contrast, adhesion is the tendency of water molecules to "stick" to other substances, such as the walls of a glass. Adhesion is responsible for the curved meniscus of water in a graduated cylinder. Phloem is responsible for sugar and carbohydrate transport in plants, while xylem transports water.

Desert plants would have different water retention and utilization strategies. They would likely use C4 or CAM photosynthesis. The C4 and CAM pathways are specific adaptations to arid conditions. They allow higher water retention, which is needed in the desert but not the rainforest. Since the main difference between these two environments is the abundance of water, even if the other options were true, they are minor differences in comparison to the need to utilize water differently.

In hypothesis-based scientific inquiry, the experiment must have an experimental group and a control group. In this case, growing plants with potassium would be the experimental group and growing plants without potassium would be the control group. Maintaining all other experimental variables, this method would allow the researcher to determine whether the plant species requires potassium. If the plants in the potassium-deprived environment die, but the plants in the potassium-rich environment survive, we can conclude that potassium is necessary for this species to survive.

The presence of potassium in the plant, leaves, or roots does not indicate it is a required nutrient. This simply indicates that the plant is capable of absorbing potassium, but does not show a dependency on potassium. Also, the movement of potassium into the plant does not indicate it is a required nutrient.

There are many necessary nutrients involved in plant development. The nutrients are used in different quantities and are grouped accordingly in two categories: micronutrients and macronutrients. Micronutrients, such as iron, are important to healthy plant growth but are used in small quantities. Macronutrients, such as oxygen, carbon, hydrogen, and phosphorus, are also used for healthy plant growth but are used in the greatest quantities.

As a result, the macronutrients are more likely to become depleted in the soil as the plant absorbs them, while the micronutrients remain abundant. Iron, as a micronutrient, is more likely to be abundant in soil than any of the macronutrients.

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.

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.

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.

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.