evst test 1

9. Draw a cross sectional sketch of a tree stem and be sure to include the vascular cambium, the xylem, and the phloem. Where is the oldest xylem located? Where is the oldest phloem located?

A cross-sectional sketch of a tree stem would show the vascular cambium between the xylem and phloem. The oldest xylem is located in the center of the stem, while the oldest phloem is located near the outer edge of the stem.

13. Describe the path of a single water molecule from the soil, through a tree, and then to the atmosphere. What are the major points of resistance along this pathway?

A water molecule enters the plant through the root hairs and moves through the root cortex to the endodermis. The endodermis contains a Casparian strip, which forces the water to pass through the selectively permeable membrane of the endodermal cells. This is important because it allows the plant to control the movement of ions and other solutes into the root. Once the water passes through the endodermis, it moves into the xylem and is transported up the stem to the leaves, where it is used in photosynthesis. The major points of resistance along this pathway include the root cortex, endodermis, and the xylem.

8. What are the advantages of being a tree as we've defined it in class? What are the disadvantages?

Advantages of being a tree include the ability to grow tall and compete for light, access to resources like water and nutrients, and the ability to provide habitat for other organisms. Disadvantages include the high cost of producing and maintaining a large body size, the risk of wind damage and other environmental stresses, and the need to invest resources in long-term growth rather than reproduction.

11) Be able to explain the differences between conifer and angiosperm wood. What are the major cell types, how do they contribute to the functional properties of wood? Know the general range in size of the different cell types (tracheids vs. vessels), and be able to explain why the diameter of the vessel or tracheid is so important. (H-P equation)

Conifer and angiosperm wood differ in terms of their cell types and structure. Conifers have mostly tracheids, which are elongated cells with tapered ends and secondary cell walls. Angiosperms have both fibers and vessels, which are wider, shorter cells with perforations in their cell walls. The diameter of the vessel or tracheid is important because it affects the rate of water transport through the xylem, as described by the Hagen-Poiseuille equation.

12. What is the difference between ectomycorrhizae and endomycorrhizae (aka arbuscular mycorrhizae)?

Ectomycorrhizae are mycorrhizal associations where the fungal hyphae do not penetrate the root cells, but instead form a sheath around the outside of the root. Endomycorrhizae, also known as arbuscular mycorrhizae, are mycorrhizal associations where the fungal hyphae penetrate the root cells and form structures called arbuscules.

where does ficks law come into place with plants

Fick's law of diffusion describes the movement of substances from an area of high concentration to an area of low concentration. In plants, Fick's law plays a role in the diffusion of gases such as oxygen and carbon dioxide through the stomata of leaves. The law also applies to the diffusion of solutes across membranes within the plant, such as the movement of sugars from the phloem into surrounding tissues. In addition, Fick's law is relevant to the movement of water within the plant, particularly in the root system. Water moves from areas of high concentration to areas of low concentration through the process of osmosis. The rate of diffusion, or flux, is proportional to the concentration gradient, the permeability of the membrane, and the surface area across which diffusion occurs. The water potential equation, which takes into account solute potential and pressure potential, is used to calculate the concentration gradient and the direction of water movement in the plant. Fick's law is used to calculate the rate of diffusion based on the concentration gradient, which is determined by the water potential equation.

16. What was the advantage of moving from the oceans to land for plants? What challenges needed to be overcome for the successful transition to land? Name a few of the different strategies for dealing with the greater risk of desiccation on land?

Moving from the oceans to land provided plants with access to more sunlight and carbon dioxide, which allowed them to photosynthesize more efficiently. However, plants also faced challenges such as desiccation, or drying out, because they were no longer surrounded by water. To overcome this challenge, plants developed a variety of strategies such as the development of a waxy cuticle on their leaves to prevent water loss, the evolution of specialized cells called stomata to regulate gas exchange, and the formation of mycorrhizal associations with fungi to increase nutrient uptake.

what are mychroyzzal fungis role in plants

Mycorrhizal fungi are important symbiotic partners of most plants. They form associations with the roots of plants and can significantly improve the ability of plants to acquire nutrients from the soil. In exchange for carbohydrates produced by the plant through photosynthesis, mycorrhizal fungi can help the plant absorb nutrients, particularly phosphorus, which can be limiting in many soils. Mycorrhizal fungi can also help plants to resist various biotic and abiotic stresses, such as drought, heavy metals, and pathogens. They can also promote plant growth and development by producing growth-promoting compounds or by improving soil structure. There are two main types of mycorrhizal fungi: endomycorrhizal fungi (also known as arbuscular mycorrhizal fungi or AMF), which penetrate the cells of plant roots, and ectomycorrhizal fungi, which form a sheath around the outside of the root cells. Both types of mycorrhizal fungi are important to plants, but they differ in their specificity to certain plant species and in their responses to environmental factors such as soil pH and nutrient availability.

15) Explain the benefits of mycorrhizal symbiosis in plants, what the tradeoff is for the plant/fungi, and the two main types that occur (AM vs. EM).

Mycorrhizal symbiosis refers to the mutualistic relationship between plants and fungi, where the fungi provide the plant with nutrients in exchange for carbohydrates from the plant. The two main types of mycorrhizae are arbuscular mycorrhizae (AM) and ectomycorrhizae (EM). AM fungi penetrate the root cells of the plant, while EM fungi form a sheath around the root. Mycorrhizal symbiosis can improve plant nutrient uptake, water uptake, and resistance to pathogens, but can also increase the risk of carbon loss for the plant.

where does ohms law come into play with plants?

Ohm's law relates to the flow of electricity in a conductor, and it does not directly apply to plants. However, the principle of resistance, which is a key aspect of Ohm's law, can be applied to the flow of water through the xylem in plants. Just like electrical current, the flow of water through the xylem is subject to resistance, which can be influenced by factors such as the diameter of the xylem conduits, the viscosity of the water, and the presence of air bubbles or other obstructions. Therefore, while Ohm's law itself does not apply directly to plants, the concept of resistance that it embodies can be useful for understanding some aspects of water transport in plants.

16) Explain what a plant meristem is, and where to find them in woody plants.

Plant meristems are regions of undifferentiated cells that can give rise to all the different cell types found in a plant. In woody plants, meristems can be found in the cambium layer, which is responsible for the secondary growth of the plant. The vascular cambium produces secondary xylem and phloem, while the cork cambium produces cork cells. Meristems are present in various parts of plants, including the root tips, shoot tips, and lateral buds. The root apical meristem (RAM) is found at the tip of the root and is responsible for the growth of the root, while the shoot apical meristem (SAM) is located at the tip of the shoot and is responsible for the growth of the stem and leaves. In addition to these apical meristems, lateral meristems are found in some plants, such as the vascular cambium and cork cambium, which are responsible for secondary growth of the plant.

10. Why do plants absorb most of their water through fine roots instead of thick, woody roots?

Plants absorb most of their water through fine roots instead of thick, woody roots because fine roots have a larger surface area to volume ratio than thick, woody roots. This means that fine roots are better able to absorb water and nutrients from the soil due to their increased surface area, allowing for more efficient uptake. Additionally, fine roots are able to explore a greater volume of soil than thick roots, which allows plants to access more water and nutrients from the surrounding soil. Thick, woody roots are typically specialized for anchoring the plant in the soil and transporting water and nutrients up to the stem and leaves. They have a smaller surface area to volume ratio, which makes them less efficient at absorbing water and nutrients from the soil.

6) Be able to discuss the major transitions from unicellular algae in the oceans to multicellular plants on land, and generally when this happened. I.e. that we have evidence that plants came on to land about 400 million years ago, started as small, non-vascular plants, that eventually developed more efficient vascular systems, and began growing upward and taking on an arborescent form by the Carboniferous period (359 million years ago), and that much of the fossil fuel we burn today came from that period.

Plants came onto land about 400 million years ago, started as small, non-vascular plants, that eventually developed more efficient vascular systems, and began growing upward and taking on an arborescent form by the Carboniferous period (359 million years ago), and much of the fossil fuel we burn today came from that period.

10) Know why plants use so much water, and where does it all go? (Know how the concentration of CO2 and H2O in the leaf vs. the air is important for driving diffusion within the context of Fick's Law)

Plants use a lot of water for photosynthesis, which involves the diffusion of CO2 into the leaf and H2O out of the leaf. Water also helps to maintain turgor pressure in plant cells, which is important for structural support and transport of nutrients. Water can also be lost through transpiration and guttation.

14) Be able to provide some rationale behind why rooting depths vary so much across different biomes.

Rooting depths vary across different biomes due to differences in soil type, nutrient availability, and water availability. In general, plants in dry biomes have deeper root systems to access water stored at greater depths, while plants in wetter biomes have shallower root systems to access water closer to the surface.

8) Know some of the major differences between plant and animal cells. You should be able to correctly label a cartoon drawing of a leaf and setm using the terms we've covered in class.

Some major differences between plant and animal cells include the presence of a cell wall in plants, the presence of chloroplasts in plant cells for photosynthesis, and the presence of a large central vacuole in plant cells. A cartoon drawing of a leaf could be labeled with terms such as stomata, mesophyll cells, and chloroplasts. A cartoon drawing of a stem could be labeled with terms such as xylem, phloem, and the vascular cambium.

what is the casparian strip in a plant

The Casparian strip is a band of cell wall material located in the radial and transverse walls of the endodermal cells of plant roots. It is a specialized structure that helps regulate the movement of water and nutrients into the plant. The Casparian strip is made up of suberin, a waxy material that is highly impermeable to water and dissolved substances. As a result, it creates a barrier that prevents water and solutes from entering the root through the cell walls between endodermal cells. Instead, water and dissolved substances must cross the plasma membranes of endodermal cells, which allows the plant to control the uptake of nutrients and water from the soil. The Casparian strip is a critical component of the root's ability to regulate water and nutrient uptake and is an essential adaptation for plants that live in variable soil environments.

4) Be able to describe the general trends in the atmospheric concentration of CO2 and O2 over the past 4.5 billion years, and the role that photosynthetic organisms played in those trends. Know the general principles of photosynthesis, the reactants and products, and limiting factors.

The atmospheric concentration of CO2 and O2 has varied over the past 4.5 billion years. Photosynthetic organisms played a major role in these trends by removing CO2 from the atmosphere and releasing O2 through photosynthesis. The general principles of photosynthesis involve the conversion of light energy into chemical energy in the form of glucose, with the reactants being carbon dioxide and water, and the products being glucose and oxygen. Limiting factors include light intensity, temperature, and the availability of water and nutrients.

3) What are the benefits of being arborescent? Are there costs or disadvantages?

The benefits of being arborescent include the ability to compete for light, access to resources such as water and nutrients, and protection from herbivores and fire. However, there are also costs and disadvantages, such as the high energy cost of building and maintaining a tall and massive structure, vulnerability to wind damage, and the risk of hydraulic failure due to embolism in xylem vessels.

15. Describe the general trends in O2 and CO2 concentrations in the atmosphere over the course of the last 4 billion years. What role did photosynthetic organisms play in these changes?

The concentration of O2 and CO2 in the atmosphere has changed over the last 4 billion years due to the evolution of photosynthetic organisms. Initially, the atmosphere was mostly composed of carbon dioxide, but as photosynthetic organisms evolved and began to produce oxygen, the concentration of oxygen in the atmosphere began to increase while the concentration of carbon dioxide decreased. This process eventually led to the formation of the ozone layer, which protected the Earth from harmful radiation and allowed life to evolve on land.

6. The __________________ forces water and solutes to pass through ______________ before entering the vascular system of the plant. Explain why this is feature of the roots is important.

The endodermis forces water and solutes to pass through the selectively permeable Casparian strip before entering the vascular system of the plant. This feature of the roots is important because it allows the plant to control what substances enter the vascular system and ensures that only desired substances are transported to other parts of the plant. The endodermis is a specialized layer of cells that surrounds the vascular tissue in plant roots. It functions as a selective barrier, regulating the movement of water and solutes into the vascular tissue. The cells of the endodermis are characterized by a distinctive band of lignin known as the Casparian strip, which is impermeable to water and solutes. This forces water and dissolved minerals to pass through the selectively permeable plasma membranes of the endodermal cells, which can actively transport ions into or out of the vascular tissue. This selective barrier helps plants maintain proper water and nutrient balance, and prevents the entry of harmful substances into the plant.

5) Describe the general transitions that took place as plants made the transition to land. What critical traits were needed to survive in terrestrial habitats? Know that fungal associations with plants likely date back to the earliest land plants.

The general transitions that took place as plants made the transition to land include the development of structures to support their weight, the evolution of a cuticle to prevent water loss, the development of stomata for gas exchange, and the evolution of a vascular system for water and nutrient transport. Critical traits needed to survive in terrestrial habitats include adaptations to drought, high light intensity, and herbivory. Fungal associations with plants likely date back to the earliest land plants, and these associations helped plants access nutrients and water.

2. What are the properties of water that relate to the cohesion-tension theory of water ascent in plants?

The properties of water that relate to the cohesion-tension theory of water ascent in plants include cohesion, adhesion, surface tension, and high specific heat. Cohesion refers to the tendency of water molecules to stick to each other, while adhesion is the tendency of water molecules to stick to other surfaces. Surface tension allows water to be pulled up through narrow tubes. High specific heat means that water can absorb and release large amounts of heat without undergoing significant temperature changes, which helps to stabilize temperature gradients in the plant.

13) Be able to briefly explain the root:shoot ratio, and why it is important. Think about cost/benefit relationships and the energy requirements of the living cells vs. their functional contribution to the tree.

The root:shoot ratio refers to the ratio of biomass between the roots and shoots of a plant. This ratio can vary depending on the plant's environment and life stage. A high root:shoot ratio is important for plants growing in nutrient-poor soils or under conditions of drought, as it allows the plant to acquire more resources from the soil. However, a high root:shoot ratio can also be energetically costly, as it requires the plant to invest more resources in root growth.

1) What is the scientific definition of a tree? What are the important differences between plants with 'secondary growth' vs. other plants with an arborescent form?

The scientific definition of a tree is a perennial plant with a single stem or trunk, supporting branches and leaves, and having a height greater than 6 m or a DBH (diameter at breast height) greater than 10 cm. Plants with secondary growth have an arborescent form, which means that they grow taller and have a thicker stem or trunk than other plants that do not have secondary growth. Secondary growth refers to the increase in diameter of stems or roots by the addition of new layers of cells called the vascular cambium, which produces secondary xylem (wood) and secondary phloem.

1. What are the three components of the water potential equation?

The three components of the water potential equation are pressure potential (Ψp), solute potential (Ψs), and gravity potential (Ψg).

11. List the three major nutrients that plants take up from the soil, and give an example of how each one is incorporated into a tree.

The three major nutrients that plants take up from the soil are nitrogen, phosphorus, and potassium. Nitrogen is incorporated into amino acids, which are used to build proteins. Phosphorus is incorporated into ATP, which is used for energy storage and transfer. Potassium is involved in ion transport and water balance in the plant.

5. Water can move through three different pathways in the root. Describe each pathway.

The three pathways through which water can move in roots are the apoplastic pathway, the symplastic pathway, and the transmembrane pathway. The apoplastic pathway refers to water moving through the cell walls and intercellular spaces of the root, while the symplastic pathway refers to water moving through the cytoplasm of cells via plasmodesmata. The transmembrane pathway involves water crossing the plasma membrane and moving through the vacuoles and cytoplasm of cells.

where is the vascular cambium in a tree

The vascular cambium is a layer of actively dividing cells located in the outermost layer of the stem of a tree, just beneath the bark. It is responsible for the secondary growth of the tree, which leads to an increase in the girth of the trunk and branches. The vascular cambium produces new cells that differentiate into either xylem or phloem, the two types of vascular tissue that transport water and nutrients throughout the plant. The xylem is responsible for transporting water and minerals from the roots to the leaves, while the phloem transports the sugars produced during photosynthesis from the leaves to other parts of the plant.

7) Know the details of the vascular cambium, and what the unifacial vs. bifacial cambium means, and why it is important for extant trees.

The vascular cambium is a thin layer of meristematic tissue that produces new xylem and phloem cells, which allows for secondary growth. The unifacial cambium produces cells only on one side of the cambial cylinder, while the bifacial cambium produces cells on both sides. This is important because trees evolved a bifacial cambium to complete more growth.

2) Know approximately how many trees there are, as well as the number of species.

There are approximately 3.04 trillion trees on Earth, according to a study published in Nature in 2015. The number of tree species is estimated to be around 60,065, according to the Global Tree Assessment.

7. Name two different meristems in trees, and then describe their role in the growth of the tree. How did this key evolutionary milestone set woody plants (i.e. trees and shrubs) apart from other plants?

Two different meristems in trees are the apical meristem and the lateral meristem. The apical meristem is responsible for the primary growth of the plant, which involves the growth of the stem and the development of leaves and branches. The lateral meristem, also known as the vascular cambium, is responsible for secondary growth, which involves the thickening of the stem and the production of new xylem and phloem. This key evolutionary milestone set woody plants apart from other plants because it allowed them to grow taller and compete for light.

12) What are the three pathways that water can move through from the soil to the stele in roots?

Water can move through three pathways in roots: the apoplastic pathway, which involves movement through the cell walls and intercellular spaces; the symplastic pathway, which involves movement through the cytoplasm of cells via plasmodesmata; and the transcellular pathway, which involves movement through the cell membrane and across the cytoplasm.

9) Know the properties of water that are relevant to long distance water transport in plants (e.g. it is polar, and has adhesive and cohesive properties, and what those terms mean). Also be familiar with the general principles of the Cohesion-Tension Theory, and the caveats. What type of conditions cause problems for vascular transport in plants? You should also know the water potential equation, the three major components (hydrostatic, solute, and gravitational) and how water potential drives the mass flow of water in plants. You should understand how changing the water potential gradient would lead to more or less flow through the plant, and why.

Water is polar, and has cohesive and adhesive properties. Cohesion refers to the attraction of water molecules to other water molecules, while adhesion refers to the attraction of water molecules to other polar surfaces. The Cohesion-Tension Theory explains how water is transported in plants, where water molecules are pulled up through the xylem due to a combination of transpirational pull and cohesion between water molecules. Conditions that cause problems for vascular transport in plants include drought, freezing, air bubbles in the xylem, and excessive salt concentration. The water potential equation takes into account hydrostatic pressure, solute concentration, and gravitational potential, and drives the mass flow of water in plants. Changing the water potential gradient affects the flow of water, with a greater gradient resulting in more flow.

an you explain how water transport and water potential equation works in plants?

Water transport in plants occurs mainly through the xylem, a specialized tissue responsible for the long-distance transport of water and minerals from the roots to the leaves. The movement of water in the xylem is driven by the difference in water potential between the soil and the atmosphere, which creates a gradient that causes water to move from areas of high potential (the soil) to areas of low potential (the atmosphere). The water potential equation is a way to calculate the potential energy of water in a system. In plants, water potential is affected by several factors, including pressure, solute concentration, and gravity. The equation is: Ψ = Ψs + Ψp + Ψg where Ψ is the water potential, Ψs is the solute potential (related to the concentration of solutes in the solution), Ψp is the pressure potential (related to the physical pressure exerted on the solution), and Ψg is the gravitational potential (related to the height of the solution above a reference point). In plants, water moves from areas of high water potential to areas of low water potential. So, for example, if the water potential in the soil is higher than the water potential in the roots, water will move from the soil into the roots. Similarly, if the water potential in the roots is higher than the water potential in the xylem, water will move from the roots into the xylem. Water transport in plants is also influenced by the cohesion-tension theory, which proposes that water molecules are pulled up through the xylem by transpiration, the loss of water vapor from the leaves. As water evaporates from the leaves, it creates a negative pressure (tension) that pulls water up through the xylem. This tension is possible because of the cohesive nature of water molecules, which stick together due to hydrogen bonding. Overall, the water potential equation and the cohesion-tension theory work together to explain how water is transported in plants.