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01 - Fall 2018/Biology of Plants/004 - Cell Division Cycle.md
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- Contractal ring.
- Not very controlled.
- One cell might get more organelles that the other.

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01 - Fall 2018/Biology of Plants/005 - Genes, Plant Tissues, and Roots.md Normal file
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> ### 005 - Genes, Plant Tissues, and Roots
> Class Notes - September 19, 2018
> Emilio Soriano Chávez
> ***
> <span style="color:#2ecc71">Biology of Plants</span>
> Fall 2018
- *Budding Yeast*
- **1959 -** First protein sequence sequenced (insulin)
- **1963 -** DNA
- **Lelend Hartwell:** Experiment in 1967
- There are approximately 9000 thousand genes in yeast
- **Gene:** Something that encodes a protein (500 aminoacids).
- 1 aminoacid = 3 nucleotides
- 1500 nucleotides
- What genes are involved in budding?
- Essential Genes: Necessary for life to develop.
- 25ºC (all yeasts grow)
- 37ºC (some yeasts die) \[temperature sensitive mutants\]
- Treat yeast with EMS, makes mutations
- 12 million base pairs
- **Genetic Screen: **Eliminate some and keep others.
- Look for ts -mutants
- Petri dish, grow yeast, division, form colonies (1000 yeast)
- **Replica Plating: **Make a copy of the original dish.
- Make 2 copies
- Copy 1 - 25ºC, all grow
- Copy 2 - 37 ºC, some do not grow
- Proteins denaturing
- Compare to original plate to see ts yeast.
> [!NOTE]
> Room at 37º C. Mark cells. Finds mutants that affect cell cycle. Concludes that cells just stop dividing. Cells that die in the middle of the cel cycle. Mutation in S phase - DNA Polymerase. 40 genes involved in cell cycle.
- Radicle and Cotyledon define axis of the plant
- **Plant Tissue:** Historically, there are 2 types of tissue:
- **Meristematic:** Called undifferentiated (means that it is nothing) in the sense that it can become anything. Become, vessel, epidermis, etc. (Growing) \[Creates ground tissue\]
- **Ground / Permanent:** More determined and divides less or not at all.
- Meristematic creates ground which differentiates (specializes) and stop dividing.
- **Apical Meristem (Tips):**
- In plants, tips are the ones that grow. And also roots. Made from meristematic tissue.
- There is a basic axis to a plant, up (shoots)-down (roots) or gravitational.
- The plant growth of apical meristem grows in these directions like the light of a double lightsaber.
- Depending on how plants grow, they can be classified as:
- **Indeterminate Plants:** They grow as long as they are alive. \[Vines, tomato, most trees\]
- **Determinate Plants:** Grow to a fixed size and stop growing. \[Most grasses (including maize), lettuce, many bushes\]
- **Meristems:**
- Primary / Apical: Located at the tips.
- Lateral / Cambium: Increases the width / thickness of the plant.
- Intercalary: Responsible for branching.
- Primary tissue pattern leads to lateral meristem, that leads to secondary tissues.
- **Simple Tissues:** Tissues get stained differently:
| Tissue | Description |
|:------------:| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Parenchyma | - Thin cell wall. <br>- Most abundant tissue. <br>- Primary sites where chloroplasts are developed. <br>- Soft in consistency (If you squish it, the stuff compressed is parenchyma tissue). |
| Collenchyma | - Thicker cell walls, particularly at the corners. <br>- Elastic and structural. <br>- Celery (strings). |
| Sclerenchyma | - Very thick and though cell walls. <br>- Dead at maturity. <br>- Fiberous or hardened. <br>- Impregnated with lignin. |
- **Complex Tissues:** Combination of simple tissue:
| Tissue | Description |
|:---------:| --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Epidermal | - Largely made up of parenchyma cells. <br>- Guard cells (open and close to let air inside) and hair cells in it. <br>- Contact with the environment. <br>- Secrete cuticule (thin layer of wax). |
| Xylem | - Center of the plant (except in leaves). <br>- Vessel elements (from vessels) and pitted tracheids (cells) to permit flow of water. <br>- Provide type of filtration (way of preventing disease). <br>- Conducts water and minerals upwards. <br>- Composed of entirely differentiated but dead cells. <br>- Empty tubes or interconnected cells (straw) that have holes that pass liquid. <br>- Some have pores on the sides or just passage in them. <br>- The holes, called pit, are areas where only primary cell wall exists. They serve a filter of 3-10 nanometers. |
| Phloem | - Made of sieve tube cells and companion cells. <br>- Primary direction is down. <br>- Carry sap or food of the plant. <br>- Carries glucose. <br>- Composed of sieve tube cells (no nuclei at maturity) and companion cells. <br>- Distributes food and substance largely made in the leaves. <br>- Sieve plate. |
- **Roots:** They anchor plants and absorb water and minerals that are in solution:
- The radicle of the seed becomes the roots. It contains the root apical meristem.
- The main root of dicots is called the taproot and grows downward following gravity (gravitropism).
- Sub roots off of the tap roots are branch/lateral roots.
- Monocots do not exhibit a taproot but instead fibrous roots that spread rather that descend.
- Roots may develop from stems or leaves as well and are known as adventious roots.
- Monocots develop from dicots.
- **Root Tips Structure:** Botanists have divided the root into 4 regions from bottom (tip) to the top:
1. Root Cap
| Part | Description |
|:-----------------------:| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Root Cap | - Protects the delicate meristem. <br>- Secretes mucilage that lubricates. <br>- Feeds microorganisms. |
| Region of Cell Division | - Aka the apical meristem. <br>- This is where all of the “growth” takes place. <br>- The root is pushing distally/downwardly through the soil. <br>- Cells in this region are being “influenced” by a quiescent (non-dividing) organizing center. |
| Region of Elongation | - Made of sieve tube cells and companion cells. <br>- Primary direction is down. <br>- Carry sap or food of the plant. <br>- Carries glucose. <br>- Composed of sieve tube cells (no nuclei at maturity) and companion cells. <br>- Distributes food and substance largely made in the leaves. <br>- Sieve plate. |
| Region of Maturation | - Able to observe layers. <br>- Cells change into particular types of cells. <br>- Root hair (projections of epidermis cells) develops in this area. <br>- Concentric cylinders. <br>- Less obvious is the differentiation of xylem, phloem, pericycle and endoderm. <br>- Branch roots develop from the pericycle. |
- Endodermal cells are surrounded by a hydrophobic band (wax).
- These bands, called Caspian strips. Forces water to go through the cell.
- Mycorhizae (infects the roots) do not penetrate past the endodermis because they can’t pass.
- **Soil:** Product of weathering and comes from bedrock underneath. Soils are a dynamic ecosystem of minerals, organize material, microorganisms, water and air.
- **Gravitropism (Geotropism):** Roots grow downwards and shoots grow against gravity (even in absence of light).
- **Phototropism (Heliotropism):** Ability of the plant to grow towards light. The shoots responds to light:
- Light turns on photosensitive genes.
- They send a signal across to the other side (mitogenic signal - causes cells to divide)
- Cells divide on one side, on the other not.
- They push the plant to one side.
- **Adventitious Roots:** Roots that do not originate from roots, they can originate from stems or leaves. They can serve purposes of support and nourishment.
- **Root Modifications:** Potatoes, cassava, jicama, turnips, beets, taro, etc. Onions, tulips, etc. are actually modified stems and leaves.
- **Root Nodules:** Colonies of rhizobacterium. They colonize the root and they fix $\text{N}_2$ from atmosphere to the plant.
- **Micorrhizae:** 80% of plants have root fungi.
- **Soil:** Five major components:
- **Mineral Matter (45-50%):** From decomposition and wheatherization of local bedrock.
- **Organic Matter (1-5%):** From local plants, animals, etc.
- **Water (2-50%)**
- **Air (2-50% of Volume)**
- **Organisms (>1%):** Both large and small.
- **Stratified Soil:**
- Topsoil
- Eluviated Horizon (Just roots, not plant decay)
- Subsoil
- Parent Material
- Bedrock
- **Water in Soil:**
- **Hygroscopic:** Adhered to soil particles.
- **Gravitational:** Water flowing due to gravity. Free flowing, air displacing.
- **Capillary:** Somewhere in between. Water that plants mainly use. Water that stays in the soil and is not hygroscopic.
- Plants can only use the capillary water.
- Too much water leads to oxygen displacement and aerobic conditions that will starve the roots.
- **Water Capacity:**
- When the gravitational water drains away, you are left with capillary water.
- The mount of water that soil can hold that is no gravitational is known as its water capacity.
- Good soil is one in which the mixture of particles is approximately 50% air by volume.