Botany

Characteristics that all plant cells must have

• a cell wall

• a large central vacuole

• a chloroplast

3 types of plant cells

• parenchyma

• collenchyma

• sclerenchyma

Parenchyma

• have thin walls and large vacuoles

• used for storage, photosynthesis, and cellular respiration

Collenchyma

• unevenly thick walls and grouped in strands and provide support to growing plants

Sclerenchyma

• extra think cell walls

• grow and then die in mature plants (provide structure in mature plants)

Dermal tissue

• outer covering of the plant

• “skin”

Vascular Tissue

• transport tissue

Ground tissue

• fills the space between dermal and vascular

• good at storing substances

Meristematic tissue

• areas of rapidly dividing cells

• unspecialized cells to become specialized

Types of Meristematic tissue

• apical meristem

• intercalary meristem

• lateral meristem

Apical meristem

• at the tips of roots and stems (taller growth)

Intercalary meristems

• along roots and stems, support longer growth

Lateral meristems

• only present in dicots (secondary growth)

• Increases the diameter of roots and stems

• vascular meristems → makes new vascular tissue

• cork cambium → makes a protective layer around stems and roots (bark)

Xylem tissue

• moves water and water soluble nutrients up the plant

• consists of cells called tracheids and vessel elements

How is xylem tissue formed?

• cells called tracheids and vessel elements die when they mature, leaving only the hollow cell wall

• water passes through the cell walls, going from cell to cell through openings called pits at end walls

Phloem tissue

• used to move food like sucrose and organic molecules

• cells called sieve-tube members and companion cells

Which structure is the first to emerge out of a seed?

roots

Functions of roots:

1. Anchor the plant into the soil

2. Absorb/transport water and minerals from the soil

3. Store carbs, water, and nutrients

Draw and label the 4 parts of the root:

Root cap

• Parenchyma cells cover the root tip which protects it during growth

Zone of cell division

• contains root apical meristem (dividing cells that allow the plant to grow)

Zone of elongation

• cells elongate to 10X their original size.

• This region pushes the root tip down through the soil.

Zone of maturation/differentiation

• cells have reached max size and become specialized

• form into dermal, ground, or vascular tissue

Draw and label a monocot root cross-section

Identify the cross-section and label

monocot root

What do root hairs do?

• increase root surface area for better water absorption

• help anchor the plant

Cortex region of roots

• consist of irregularly shaped cells with lots of air spaces

• cells have large vacuoles in which they store food (starch in amyloplasts)

Amyloplast

specialized vacuole for starch specifically to be stored

what does the endodermis do for roots?

• acts as a waterproof barrier for the vascular tissue

• keeps harmful substances out and keeps nutrients in

Draw and label a dicot root cross-section

Identify the type of cross section and label it

dicot root

tap root

dicots

fibrous roots

monocots

Types of stems

• herbaceous

• woody

Herbaceous stems

• soft, flexible, green stems

• contain chloroplasts (only type of stem capable of photosynthesis)

Woody stems

• hard and rigid

• bark protects plants from herbivores, insects, and fires

Stem functions

1. Supports leaves and flowers

2. Transport substances between roots and leaves

3. May produce food

4. Stores substances

Draw and label a monocot stem cross section

Identify this cross section and label

monocot stem

Draw and label a dicot stem cross section

Identify the cross section and label

dicot stem

function of guard cells and stomata

holes that allow gasses to enter and exit

epidermis importance in stems

• secrete a waxy substance to create the cuticle (waterproof covering)

• contain guard cells and stomata

cortex and pith in stems

• contain parenchyma cells

• loosely packed with lots of air spaces

• pith stores water and space

How do plants grow wider?

• lateral meristems (vascular cambium and cork cambium)

• vascular cambium produce secondary xylem (wood) and secondary phloem (bark)

• cork cambium develops from parenchyma cells in the cortex

bark

everything outside of the vascular cambium

Primary function of leaves

convert solar energy into chemical energy

Why are leaves broad and flat

to maximize surface area for max light absorption and photosynthesis

Draw and label a leaf cross section (dicot)

Identify and label the cross section

dicot leaf

Identify and label the leaf cross section

monocot leaf

What kinds of leaves have specialized mesophyll

dicot leaves

Why does the epidermis of leaves have a waxy cuticle

to prevent evaporation

Mesophyll region

• ground tissue made of cells specialized for photosynthesis (lots of chloroplasts)

palisade mesophyll

• where light absorption happens

• made of long thin cells arranged side by side

• top gets exposed to sunlight, bottom gets exposed to gasses from the spongy mesophyll region

Spongy mesophyll

• contains many air spaces for storage of gasses and water

Monocot vascular arrangement

parallel

Dicot vascular arrangement

branching

Draw and label a diagram of a flower

Vegetative plant reproduction

• asexual (no gametes)

• only one plant required

• less specialized structures (faster)

• all offspring are identical

Sexual plant reproduction

• union of two gametes making a zygote

• more complex structures (takes more time, energy, glucose)

• offspring are genetically different

Female parts of the flower

Pistil/Carpel

• stigma

• style

• ovary

Male parts of the flower

Stamen

• Anther

• filament

Stigma

• sticky lip of the carpel which catches the pollen (where pollination happens)

• female

Style

• stalk that supports the stigma

• female

Ovaries

• swollen base of the carpel containing ovules

• female

Anther

• makes and stores pollen

• male

filament

• holds up the anther

• male

Petal function

• attracts insects and pollinators

Sepal function

• protects reproductive organs from external damages

Monocot flower markers

• leaves with parallel veins

• flower petals in 3s

Dicot flower markers

• leaves with branching veins

• flower leaves in 4s or 5s

Pollination

transfer of pollen from the anther to the stigma of the same species

Mechanisms of Pollination

• Cross-pollination

• Self-pollination

Cross-Pollination

plant receives pollen from another plant (ensures genetic diversity)

Self-pollination

Flowers can pollinate themselves of another flower on the same plant → may cause inbreeding and loss of genetic diversity

How does pollen move between flowers?

• By wind - plants may produce copious amounts of pollen and lack colour and scent

• By animal/insect - plant smells good, is brightly coloured to attract insects (nectar as a reward)

Pollination Process

1. Pollen lands on stigma and wall ruptures

2. If compatible, pollen tubes grow down the style into the ovary

3. The pollen enters the ovary through the micropyle and releases a nucleus containing DNA

4. the pore then closes so that no other pollen can enter

5. fertilization occurs forming a zygote (egg + pollen) and the endosperm (nutrient tissue)

Seed development

after fertilization, each ovule becomes a mature seed, containing an embryo

Fruit development

ovary wall thickens, forming a fruit that encloses the seed

What is the point of seed dispersal?

• it increases the survival rate of offspring since they don’t need to compete for light, water, and nutrients in the same location

• they are spread out

Describe germination

• seed will eventually start to grow again in favorable conditions

• the root emerges from the seed first

Growth promoters

• auxin

• cytokinin

• gibberellins

Growth inhibitors

• ethylene

• Abscisic acid

Auxin

• stimulates elongation of plant cells

• found in apical meristem buds, young leaves, and fast growing tissues

• creates apical dominance

Apical dominance

when plants mostly grow upwards

Cytokinin

• promotes cell division and differentiation

• stimulates proteins needed for mitosis

• delays aging of leaves and fruit

Gibberellins

• produced by apical meristems

• promote growth of taller, stronger plants and ones that flower early

• stops dormancy in seeds

• used worldwide commercially to increase fruit size

Ethylene

• gaseous hormone released by ripening fruit, dying leaves, and flowers

• easily diffuses through cells

• weakens cell walls of unripe fruit and breaks down complex carbohydrates into simple sugars

Abscisic acid

• synthesized in mature green leaves, fruits, and root caps

• blocks growth promoting hormones

• promotes dormancy

• blocks intake of CO2 by controlling stomata (blocks photosynthesis)

Tropisms

• directional growth response to stimuli in the environment

• affects the production of hormones which influence how the plant grows

Phototropism

• response to light

• due to different amounts of auxin on the light and dark sides of the plant

Gravitropism

• response to gravity

Positive gravitropism

• causes roots to grow downwards

Negative gravitropism

• causes plants to grow downwards

Gravitropism hypothesis

statoliths (vacuoles containing starch grains) settle to the low parts of the root, directing growth downwards

Thigmotropism

• response to contact

• evident in vines that grow around structures

Nastic movements

• rapid plant movements caused by a stimulus

• non-directional, reversible, and can be repeated

Ecological succession

the change in an ecosystem that happens when one community replaces another; It results from changes in abiotic and biotic factors

Primary succession

• The establishment of a community in an area of exposed rock that does not have any topsoil.

• ex. a glacier has melted and left barren rock behind. A volcano has erupted and the bed of hardened lava has created new barren rock