Plants... Fucking Plants... Flashcards
What are plants?
Plants are:
- Autotrophic organisms which are able to synthesize all required organic compounds from inorganic substances using sunlight as an energy source.
- Multicelled and Eukaryotic
- Evolved from green aquatic algae about 500 million years ago
- Over a quarter million plant species are known today and are found in many diverse regions, from desert areas to polar areas.
- Have cell walls made of cellulose (Beta-glucose linkage)
When is a plant vascular?
Vascular plants contain distinctive areas of specialized tissue called xylem and phloem
What is Xylem?
Xylem is the vascular tissue in plants that conducts water and minerals from roots to the rest of the plant in one direction
- Contains cells called tracheids, thus are called tracheophytes
- Contains cells called a vessel member
- Both Vessel Member and Tracheid cells are dead at maturity
- Xylem also aids in supporting the plant and is what makes up the woody part of the stem or tree trunk
- Xylem can only transport upwards.
What is Phloem?
Phloem is the vascular tissue in plants that carries sugar from the leaves to the rest of the plant.
- Phloem can transport things both upwards and downwards as needed.
- The main conducting cells are called sieve-tube members. Sugars made by photosynthetic leaves are loaded into these tube members with the help of companion cells. Sugars are then unloaded for growth or storage
What is a cuticle?
A cuticle is a hydrophobic waxy coating that surrounds the leaf and prevents it from losing water
What is transpiration?
Transpiration is water evaporation in plants
How does CO2 enter the plant?
Co2 enters the plant through special openings in the leaf called stomata.
- Stomata allow the Co2 to diffuse through into the leaf.
- CO2 must combine with water before it is allowed to be absorbed by leaf cells
What are stomata?
Stomata are openings in the leaf that allow water to evaporate and allow CO2 to come into the leaf.
- In most plants, stomata stay open during the day when photosynthesis can occur. This results in a loss of water and an uptake of CO2 into the cell
- At night stomata are usually closed. This leads to the conservation of water and CO2 accumulation.
- Stomata are opened up by guard cells.
What are guard cells?
Guard cells open and close stomata based on water content in the plant.
- When the plant is full of water, guard cells swell up opening up the stomata.
Why is transpiration of water in plants important?
Xylem pull water and nutrients up the roots and into the rest of the plant.
- The only way it can do this is if there is a negative osmotic pressure up top that pushed the water upward.
- The plant must lose water through transpiration in order to create that negative pressure.
What determines if a soil is suitable for plant growth?
Aeration and H20 capacity will determine if the soil is suited for plant growth.
What are roots?
Roots are specialized plant structures:
- grow downward
- Absorbs H20 and minerals
- Anchors the plants
- Stores food and releases it as needed
- All begin with a single root (primary root), but then grow differently into smaller roots (secondary roots)
- Root surface area is increased enormously by outgrowths called root hairs.
What is the meristem?
The meristem is the root tip
- This is an area of active cell division. We see new plants grow and older plants lengthen
What are the structures of the root?
A root contains:
- Epidermis
- Cortex
- Endodermis
- Stele
- Nodules (in N2 fixing plants)
What is a roots Epidermis?
The roots epidermis is the outermost layer of the root which includes the root hairs.
What is a root’s cortex?
A root’s cortex stores starch and contains parenchymal cells
What is a root’s Endodermis?
A root’s endodermis is the innermost layer of the cortex
- its associated with a waxy tissue band called a Casparian strip
- This strip is involved with controlling the uptake of water and dissolved nutrients
What is the root’s stele?
The root’s stele:
- Layer of cells inside the epidermis containing xylem and phloem cells.
- This is also called the vascular cylinder.
- Cambium tissue lies between the xylem and phloem, and will add more layers of xylem and phloem to thereby thicken the root
- The outer part of the stele is a layer of cells called a pericycle. These cells can initiate the development of secondary roots.
What are root nodules?
Root nodules:
- On the roots of legumes such as peas and beans, we see swellings called root nodules that contain nitrogen-fixing bacteria which convert atmospheric N2 into forms required by the plant, such as NO3- and NH4+
Why do plants need to absorb NH4+ and NO3-?
Plants use NH4+ and NO3- to form amino acids, proteins, and other nitrogenous compounds?
How do plants get the NH4+ and NO3- they need?
Plants get their nitrogen either through:
- root nodules: Use bacteria in the nodules to fix Nitrogen in the air into forms required by the plant. NH4+ and NO3-
- Nitrification: Bacteria in the soil break down dead organisms to release NH4+. The NH4+ is then oxidized into NO3-. These are both brought up into the plant through the root.
What is nitrification?
Nitrification is the process in which bacteria break down dead organisms in the soil to release NH4+, that is later oxidized into NO3-.
What is denitrification?
Denitrification is the process by which the plant uses the NH4+ and NO3- taken up by the soil and converts it into N2 and a small amount of N2O
What is the nitrogen cycle?
The nitrogen cycle is the process by which plants use nitrogenous molecules from the soil and then produce N2 gas.
What is mycorrhizhae?
Mycorrhizae is the association of a nonpathogenic fungi with roots
- Materials absorbed by the roots passes first through the fungi which allow them to gain nutrients
- The fungus increases the surface area available for water and nutrient uptake. Some trees grow very poorly without this fungus.
- Orchids also depend on this symbiotic relationship called mutualism
What is dermal tissue?
Dermal tissue covers the plant and provides it protection
- Cuticle: Waxy layer that prevents evaporation of water from the plant
- Epidermis: layer of tightly packed cells that covers the primary plant body. It is only a single cell large and many epidermal cells have extensions as root hairs.
What is ground tissue?
Ground tissue is the third plant tissue type besides vascular and dermal tissue it is composed of:
- Parenchyma cells
- Collenchyma cells
- Sclerenchyma cells
What are parenchyma cells?
Parenchyma cells are a type of ground tissue:
- Most abundant ground tissue
- Thin walls seen in roots, stems, and leaves
- Storage, secretion, and photosynthesis involvement
What are collenchyma cells?
Collenchyma cells are a type of ground tissue:
- Cell walls are thick and provide flexible support for the growing stem
What are sclerenchyma cells?
Sclerenchyma cells are a type of ground tissue:
- Very thick cell walls that provide protection and support
- contain lignin, this is the second most abundant polymer in the world second only to cellulose.
- Lignin and cellulose both work together to provide strength and support
- Lignin also forms a barrier against invaders like fungi or insects
What is lignin?
Lignin is a polymer created by sclerenchyma cells
- It works with cellulose to provide support and strength to the plant.
- It also forms a barrier against foreign invaders like fungi or insects
