SBI3U1 - Final Exam

Basic needs of plants

Capture energy from the sun and photosynthesize, adjust position of leaves to maximize sun exposure, protect themselves by producing substances, communicate to other plant cells to respond to environmental changes, absorb nutrients through roots/mycorrhizal fungi, take in water, exchange gasses, reproduce

Phylogeny

Evolved from charophytes, a type of green algae 425-490 million years ago accounting for similarities between plants and green algae (protists), both contain chlorophyll, cellulose cell walls, and store carbs as starch

Dermal tissues definition

Two tissues types: Epidermis and periderm. Outermost cell layers, often have thicker walls and are covered with a waxy cuticle. In some plants, epidermis may eventually be replaced with periderm (like bark)

Dermal tissues functions

Protect against injury, herbivores, disease, and water loss. Facilitate gas exchange through pores in tissue

Ground tissue functions

Photosynthesis, storage, support

Parenchyma

Type of ground tissue with thin walls which contain many chloroplast and large vacuoles. Forms most of tissue in leaves/stems/roots

Ground tissue functions

Perform cellular functions, store carbohydrates, support and protect plant body

Meristematic tissue

Area of actively dividing undifferentiated cells (plant version of stem cells), found in areas of plant growth

Meristematic tissue functions

Facilitates new growth in roots and shoots, in buds and nodes of stems, space between xylem and phloem, under epidermis in some plants

Xylem

Thick-walled cells of vascular tissue, dead at maturity

Phloem

Thin-walled cells of vascular tissue, living at maturity

Functions of vascular tissue

Provide transport pathways for water, nutrients, and other molecules. Supports plant body

Leaf structure

Both sides are covered in dermal tissue, veins contain vascular bundles (xylem and phloem) to carry nutrients in/out of leaf, top of leaf has waxy cuticle to prevent from water loss/damage

Stomata

Openings on the underside of leaf that facilitate gas exchange and water loss (transpiration)

Guard cells

Regulate opening/closing of stomata using osmosis

Mesophyll definition

Type of ground tissue under epidermis

Palisade mesophyll

Tightly packed cells with high concentrations of chloroplasts for photosynthesis

Spongy mesophyll

Loosely packed cells with a lower concentration of chloroplasts. Spaces between cells facilitate gas exchange between stomata and rest of leaf

Human uses of leaves

Medication, food, flavouring, respiration, decoration, shelter, ceremony

Herbaceous stems structure

Xylem and phloem are arranged in vascular bundles, xylem always inwards and phloem always outwards. Arrangement can be uniform (dicots) or scattered (monocots)

Woody stems structure

Meristematic tissue called vascular cambium produces new xylem to inside and new phloem to outside

Wood structure

Multiple layers of xylem tissue

Herbaceous stem examples

Garlic, onions, tulips

Wood-like herbaceous stem examples

Banana trees, bamboo, coconut trees

Woody stem examples

Mango trees, oak trees, peanut bushes

Tubers/bulbs

Underground stems for food storage in some plants

Rhizomes

Horizontal underground stems

Stolons/runners

Stems that grow along soil instead of upright

Human uses of stems

Paper, utensils, rubber, food, instruments

Fibrous roots

Many small roots growing downwards with many smaller lateral roots

Taproots

One large main root that grows downward, with some smaller lateral roots

Root system function

Anchors and supports plant’s stem and leaves

Root cap function

Protects the tip of each root and produces a slippery substance to help root permeate

Meristem function

Produces new cells

Root hairs function

Increase surface area for absorption

Root cortex function

Region of parenchyma under epidermis that stores carbs and transports water from xylem to epidermis

Casparian strip function

Wax-like strip that runs through cell wall of endodermal cells which prevents backflow of water and protects from pathogens

Mycorrizhae definition

Symbiotic relationship between plants and fungi observed in 90% of plants. Fungi’s mycelium breaks down and absorbs nutrients, transporting them to the plant.

Plant symbiosis with bacteria

Since they can’t absorb nitrogen from the atmosphere, and require it to produce DNA, RNA, and amino acids, bacteria turn nitrogen into ammonia which is usable by plants, and plants provide glucose in return.

Human uses of roots

Food sources, dyes, pesticides

Asexual reproduction in plants

New plants from eyes on tubers, modified leaves can produce buds that form new plants, suckers (new shoots that grow from a plants’ roots)

Benefits of asexual reproduction

Advantageous traits from parent will be passed on, saves energy because plant doesn’t have to produce reproductive structures like flowers or cones, only needs one plant, plantlets produced have a higher survival rate than seedlings

Grafting

Cutting a young branch from a plant and attaching it to the stem of another plant. Both plants need to be closely related. Vascular tissue will slowly fuse

Sexual reproduction in angiosperms

Each flower contains both male and female reproductive organs (stamen is male and pistil is female). Uses cross- or self-pollination

Cross-pollination

Transfer of pollen grains from one plant to another

Self-pollination

Transfer of pollen from one flower to another on the same plant

Examples of pollinators

Bees, butterflies, birds, bats, beetles, flies, wasps, ants, wasps

Genetic prevention of inbreeding in angiosperms

Incomplete flowers (some flowers don’t have fully developed pistils/stamen), each plant produces either one or the other organ, eliminating self-pollination

Molecular prevention of inbreeding in angiosperms

Self-incompatibility is when pollen is molecularly incompatible with the ovum in the same plant, so it won’t produce any zygotes from self-pollination

Structural prevention of inbreeding in angiosperms

Longer distance between stigma and anther, reducing likelihood of self-pollination

Pollinator attraction in angiosperms

Bright colours, big pollen load, large stigma, pollen guides/indicators, nectar

Seed production in angiosperms

Pollen from the anther of the stamen of one flower is transported to the stigma of the pistil of another flower and pollen moves down the style. Fertilization happens in the ovary, resulting in seeds

Seed production in gymnosperms

Reproduction occurs in cones, small, yellow male cones produce grains of pollen which fall into large brown female cones and fertilize the ovules, which produces seeds

Benefits of sexual reproduction

Increases genetic diversity, seeds dispersed to new locations, seeds can be dormant

Costs of sexual reproduction

Takes a lot of resources and requires two plants

Seed structure and function

Protects and nourishes enclosed embryo. Seeds contain embryos, tissue to provide nutrients to the embryo, protective coat

Fruit function and structure

Fleshy structure derived from flowers which contains seeds, its function is to spread the seeds

Structural macronutrients

Very large quantities, Carbon, Hydrogen, Oxygen

Other macronutrients

Large quantities, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur

Micronutrients

Small quantities, boron, chlorine, copper, iron, manganese, molybdenum, nickel, zinc

Growth definition

Process of a body increasing in size via cell division and enlargement

Differentiation definition

Process in which a cell becomes specialized to perform different functions

Factors that affect growth: atmospheric CO2

Plants need CO2 for photosynthesis. Studies have shown that the level of atmospheric CO2 changes the gene expression that controls stomata production

Factors that affect growth: Temperature

Opening/closing of stomata is affected by temperature. It acts as a signal for plants to begin a developmental stage like flowering or seed germination

Factors that affect growth: Soil composition/pH

Soil allows roots to anchor themselves, water absorption, and provides roots with air and minerals. PH of the soil determines nutrient absorption and most plants prefer mildly acidic

Factors that affect growth: Light

Certain wavelengths like reds and blues are more desirable for plant growth

Photoperiodism

A plant’s response to changes in day length. Short day plants flower when darkness exceeds critical night length. Long-day plants flower when darkness is less than a critical night length.

Phototropism

A plant bends/grows directionally according to position of light

Gravitropism

Response to gravity

Thigmotropism

Response to touch

Hydrotropism

Response to water

Plant growth regulators

Chemicals produced by plant cells that regulate growth/differentiation called hormones, which are usually produced in the tissues where they’re used

Types of transport in cells

Passive and active

Passive transport

Doesn’t require energy, therefore relies on a difference in concentration gradient

Types of passive transport

Simple diffusion, facilitated diffusion, osmosis

Solvent

Liquid that dissolves something

Solute

Something that dissolves in a liquid

Solution

Mixture of solute and solvent

Auxin

Promotes cell division, results in new roots, shoots, and fruit growth, promotes upward growth, allows plants to bend directionally for phototropism

Which hormones regulate normal shoot and root development

Interactions between cytokinins and auxin

Cytokinins

Promote cell division, stimulate lateral growth, delay cell aging, inhibit protein breakdown and stimulate synthesis

Gibberellins

Stimulate lengthening of stems for fruit production, induces bolting (rapid stem elongation), induces leaf expansion, induce transitions to next developmental stage, influences fruit size

Ethylene

Growth inhibitor/stress hormone, stimulates leaf loss in drought, stimulates fruit ripening, produced at the site of wounds, prevents new shoots from growing

Abscisic acid

Growth inhibitor, promotes stomata closure, seed/bud dormancy, inhibits transition from embryonic stage to germination during poor conditions

Cytokinins absent, auxin present

Cells enlarge, no division

Cytokinins present, auxin absent

No effect on cells

Cytokinins higher than auxin

Cells differentiate into shoots

Auxins higher than cytokinins

Cells differentiate into roots

Applications of auxin

Herbicides, stimulate ethylene production to ripen fruits

Applications of cytokinins

Prevent spoiling of vegetables and cut flowers

Applications of ethylene

Applied to ripen fruits

Applications of ABA

Applied to plants to induce dormancy for shipping

Applications of gibberellins

Applied to plants to reverse dormancy

DNA meaning

Deoxyribonucleic acid, fundamental molecule for life

Nitrogenous bases

The “rungs of the DNA ladder”, the order of Adenine, Thymine, Cytosine, and Guanine determine the proteins produced and therefore the traits of an organism.

Ribosomes

“Read” the order of nitrogenous bases in DNA to create proteins.

Chromosomes

A structure where DNA is carried for both prokaryotes and eukaryotes.

Plasmids

Prokaryotes and some protists contain plasmids which are small circular pieces of DNA that can be picked up or passed between cells.

Chromatin

Long unwound strands of DNA

How many chromosomes do humans have

Usually 46 in each cell