Leaves, Stem, and Roots Flashcards
Functions of leaves
-Main job is to perform photosynthesis(needs light, H2O, and CO2)
-Absorb energy in a organelle called a chloroplast which contains photopigments(chemicals which absorb specific wavelengths of light)
-Gas exchange: take in carbon dioxide and remove oxygen + water vapour
-Protection from herbivores
Structured in Leaves
1: Veins
2: Petiole
3: Blade
Veins
Vascular system in leaves and consist of
1.Xylem:
- hollow tubes with thick walls thay carry water
- Found in the outside parts of veins
2.Phloem:
-Carry food materials in solution from the leaves to other parts
-Inside part of vein
Petiole
stalk connecting leaf to stem
Blade
broad, flat portion of the leaf
Internal structure of leaves
-Cuticle
-Mesophyll
Cuticle
-waxy, waterproof layer on outer surface
-prevents water loss and provide physical layer of protection against bacteria, mould, and insects
Epidermis
- outermost layer
- non-photosynthetic and transparent
Mesophyll
-middle of leaf
-cells contain chloroplast; photosynthetic cells
-vascular bundles(veins) are embedded
two types of cells in Mesophyll
-Palisade cells
* Layer of columnar cells just beneath the upper epidermis
* Most photosynthesis occurs here
-Spongy cells
*Layer of irregular shaped cells just above the lower epidermis
*Spaces between cells aid in gas exchange
Other structures
Stomata: Adjustable pores which regulate the diffusion of CO2 and H2O
Guard cells: Pair of cells that regulate gas and water exchange with the air
Leaf specializations
-Most plants use leaf specializations for protection
*Nicotine is produced by tabasco leaves to deter herbivores
* Cactus plants have spikes
-Some plants(gymnosperms) have chemicals which prevent their cells from freezing in the winter
Human uses of leaves
-Nutrition
*Dark leafy greens contain minerals and vitamins
*Waxy cuticle can be used to make polishes for cars and furniture
-Toxins produced by leaves can be used to kill cancer cells(vincristine)
-Some leaves produce psychotropic chemicals meaning they alter the mind(marijuana leaves make THC)
Functions of stems
-Support the leaves and reproductive structures
-Transport materials throughout the plant body
-Raise leaves to maximize exposure to sunlight
-Some store food
Stem structures
- Herbaceous stems
- Woody stems
Herbaceous stems
-contain soft, green, juicy tissues
-found in plants that live for less than two years
Woody stems
-contain thick, tough tissue(wood)
-found in plants that live for more than 2 years(trees and shrubs)
Herbaceous Stems
1.In monocots
*vascular bundles(xylem and phloem) scattered throughout the stem
- In dicots
*vascular bundles arranged in ring in cortex
*vascular bundles consist of outer phloem and inner xylem
Woody stems
-Can grow thicker due to vascular cambium(layer that divides to form xylem and phloem cells)
1) In monocots
*vascular bundles are scattered(palm tree)
2) In dicots
*annual rings are present
*result of new xylem produced each growing season(maple tree)
Parts of Woody Stems
- Pith: storage
- Wood: support and transport of water(it’s the xylem)
- Vascular cambium
*produces xylem and phloem
*responsible for increasing width - Bark: Consists of all of the tissues outside the vascular cambium(phloem, cork cambium, and cork)
- Cork cambium is what produces cork
- Cork- protection from environment
human uses for stems
- Fuel: wood and ethanol
- Food: sugar cane, yams, asparagus
- Dyes
- Medicine: the pain relieve salicylic acid is made from bark
- Textiles: flax is used to make linens, bamboo used in clothing
Functions of roots
-Anchor plant: preventing erosion
-Support stem
-Absorb water and minerals from the soil
-Site of starch storage produced in leaves
Types of Roots
Fibrous vs. Taproot
Fibrous root system
- Fibrous root systems consist of a large number of branches, slender roots called lateral roots(monocot)
- Taproot systems consist of one large root (dicot) covered in little root hairs
*Carrots, beets, turnips and radishes
Roots specializations
-Most roots are made for efficiently absorbing water and nutrients, anchoring the plant and storing carbs
-To help absorb nutrients, plants have a mutualistic relationship with mycorrhizal fungi
*the fungi release digestive enzymes that break down organic matter which the plants can then absorb and in return the fungi receives carbs made by the plant
-Also have relationship with nitrogen fixing bacteria
*bacteria convert nitrogen from the air into a fork the plant can use
*the bacteria receives carbs made by the plant
Human uses for roots
-Food
*many vegetables we eat are roots
-Drinks
*root beer was originally made from the sassafras plant root
*dyes
-Medicine
*kava kava root has been shown to to reduce anxiety
*valerian root can be used to relieve insomnia
There are 2 parts of mesophyll
-Palisade mesophyll
-Spongy mesophyll
