Biology IB HL Chapter 9

Loss of water vapour from leaves and other aerial parts of the plant.

• Blade: The leaf part
• Petriole: The connection of the blade to the stem
• Stem: The stem

• Cuticle
• Epidermis
• Xylem
• Phloem
• Palisade Mesophyll
• Spongy Mesophyll

Protects the plant against water loss and insect invasion.

Protects the plant

• Is the specialized water conducting tissue of terrestrial plants.
• Composed of many cell types (tracheids and vessel elements)
• Carries water to the leaves.
• Supports the plant.

• Found in xylem.
• Evolved after tracheids as the water transportation structure that makes up xylem.
• Water moves laterally along a long stretch where the two vessels, the ending and the continuing are run side by side.
• Pores allow rapid water transport.
• Found only in angiosperms.
• Secondary walls are lignified, primary walls include pits and pores that allow water to move laterally.

Organic complex that strengthens the cell walls of vascular plants, waterproofs and protects against pathogens.

• Found in xylem.
• Evolved first.
• Found in all plants.
• Are single celled and shorter than vessel elements.
• They have pits and modified pits along their walls to allow water to move between cells.
• Is a hollow cell with no cytoplasm or nucleus.
• Dead and devoid of protoplast
• !!!! its head is like a condom so it’s less efficient

• Minerals must be transported along with water. There are three major processes that allow mineral ions to pass from the soil to the root.
• Diffusion of mineral ions and mass flow of water carries minerals (passive flow through mass or bulk flow)
• Action of fungal hyphae (fungi gain carbon, plant gains mineral ions and increased surface area.) MYCORRHIZA
• Active transport of K, NO3 or PO3 using the ATP and O2 produced by root hairs through protein pumps

• Provides mineral ions and water uptake for the plant
• Successful due to root hairs and extensive branching.
• Zone of maturation, zone of elongation (G), zone of cell division (apical meristem) (M)
• Root hairs: higher solute concentration for osmosis and increased surface area
• Root cap: protects apical meristem

higher solute concentration for osmosis and increased surface area

Carries the products of photosynthesis to the other areas of the plant.

Densely packed cylindrical cells carry a large number of chloroplasts. (on the top of the plant)

Loosely packed cells with few chloroplasts. Air spaces provide gas exchange surfaces. There are stomata and guard cells right underneath

• Stomata can only close on a short term basis. The opening and closing is controlled by turgor pressure of guard cells with uneven cell wall thickness.
• Blue light triggers ATP powered proton pumps in the guard cells and active transport of K+ into the cell occurs. This causes inward water movement through osmosis and increases turgor. Abscisic acid makes K+ and water diffuse out.

Produced in the roots during droughts. Makes K+ and water diffuse out of the guard cells and closes stomata.

• Cools down the plant and sun soaked leaves and stems
• Allows gas exchange
• Provides minerals to the plant through bulk flow

• Continuous column of water is maintained,
• Water moves down concentration gradient from leaf to the atmosphere.
• Water lost through transpiration is replaced by water in the vessels (air spaces in the leaf have high water vapour concentration)
• The vessel water column is maintained by cohesion (H bonds between water molecules) and adhesion (H bonds between the water molecules and xylem)
• Tension occurs in the columns of water in the xylem
• Water is pulled from root cortex to xylem cells
• 6. Water is pulled from the soil into the roots

Lower stomatal density has been observed due to increased CO2 levels in the atmosphere.

Speeds it up by opening stomata.

Decreases it, concentration gradient is less.

Speeds it up, humid air around stomata is carried away

Increases it, more water evaporates.

Soil water must keep up with transpiration rates. If the water in the soil is insufficient, turgor will be lost and the stomata will close.

High Co2 levels cause turgor loss and decreased transpiration. (biological pathways are activated when CO2 falls so stomata opens)

• Arid climates
• Small thick leaves to reduce transpiration.
• Reduced number of stomata
• Stomata are located in crypts or pits on the leaf surface for higher humidity near stomata
• Thickened waxy surface reduces water loss (trichomes)
• Hair like cells on the leaf surface trap water, increasing humidity
• Become dormant or shed their leaves during dry months
• Succulents store water

Hair like structures that reflect light and secrete chemicals.

• High salinity
• Succulent to dilute concentrations
• They secrete salt through salt glands
• Can compartmentalize Na+ and Cl- in vacuoles.
• Thick leaves and sunken stomata reduce water loss
• Surface area of leaves is reduced.

• C3 is the most common
• CAM is when stomata are closed during the day and CO2 is incorporated at night.
• C4 is when stomata are open during the day but there is rapid CO2 intake.

• Xylem transports in one direction, phloem can transport in both directions.
• Xylem is made of dead cells, phloem is made of alive cells.
• In xylem, a continuous tube of dead cells an unbroken column of water, the movement is passive. In phloem, the cells are alive and they enable substances to be loaded by active transport.
• In xylem, the walls are thickened by lignin to withstand negative pressure. In phloem, companion cells carry out cell functions and supply energy for active transport into phloem
• Xylem transports water and minerals passively from roots to leaves. Phloem transports sugars, RNA and hormones to all parts of the plant by mass flow.

• Sieve tube members: lack nucleus and cytoplasm
• Companion cells: has a nucleus and dense cytoplasm
• These two are connected through plasmodesmata
• Sieve plates: are between different sieve tube members, has pores

Translocation from source to sink

Parts of a plant where starch is hydrolyzed or glucose is produced.

Where sugars are either produced or consumed.

Yes, a tube or bulb act as sinks in the summer and sources in early spring.

• Any fluid that moves out of the normal transport system of plants.
• Resin, gum, saps, latex

• Solution of water in which organic molecules are dissolved.
• Carries sugars, amino acids, plant hormones, RNA (plant communication)

• At source, sugars are loaded into sieve tube using active transport (using specialized proteins called cotransport, proton pumps) chemiosmotic process. This causes osmosis from surrounding cells
• Uptake of water at source causes positive hydrostatic pressure
• Raised hydrostatic pressure causes the phloem sap to move passively to sink
• Sugars are removed at sink (active transport, cotransport proteins) Sugars are changed to starch at sink which exerts no osmotic pressure
• Xylem recycles relatively pure water, carrying it from the sink back to the source

• Its walls are rigid so hydrostatic pressure is achieved.
• Phloem tissue occurs in all parts of the plant, not just the stem.

• Phloem
• The provide “life support” for the sieve element cells. Plasmodesmata connects them to sieve tube elements.

• Phloem
• No nucleus, ribosomes or vacuoles, reduced cytoplasm (requires companion cells to stay alive)

Fibers of sclerenchyma cells

It is the packing material between other cell types and and helps transfer materials to the sieve elements and companion cells.

• Radioactively tagged compound C
• Autoradiography
• Or we can use aphids

• Cortex: Made mostly of parenchyma cells, unspecialized cells between epidermis and endodermis, has chloroplasts
• May store resin, latex etc.
• Xylem - Cambium (between the two from which they grow) - Phloem
• Pith: Soft, spongy parenchyma cells that transport nutrients.

Phloem outside xylem inside

• Dermal: epidermis
• Ground: parenchyma
• Vascular: xylem + phloem
• All of these are derived meristematic tissue

• Composed of aggregates of small cells that have the same function as stem cells.
• When cells divide, one of the always remains meristematic and one differentiates into a derivative so indeterminate growth is achieved.

• Annuals: 1 year
• Biennials: 2 years
• Perennials: many years, usually die of infection or env. Factor

Apical and lateral

• Primary growth in length
• At the tip of the root or the tip of the shoot
• Results in herbaceous non-woody stems and roots

Apical meristem and the surrounding development tissue cause primary growth (height) through mitosis and cell division.

• Secondary growth
• Allows the growth in thickness
• Develops from the main stem as shoots and branches
• Allows competition and taking advantage of favorable conditions
• Trees and shrubs have two different kinds of lateral meristems:
• Vascular cambium: between xylem and phloem, produces secondary xylem (wood) and phloem
• Cork cambium: produces cork cells for the outer bark

• Shoot apical meristems
• Root apical meristems
• Vascular cambium (lateral meristem)
• Cork cambium (lateral meristem)

• Environmental factors
• Receptors
• Genetics
• Hormones

• Specific cells have proteins in their plasma membrane, cytoplasm or nucleus that allow them to receive environmental stimuli
• Proteins activate upon specific stimuli and allow for different metabolic pathways

• Plant hormones affect various tissues differently.
• Plant hormones require a great deal of interaction within themselves for the appropriate response
• Plant hormones are produced everywhere in the plant,

Complex set of hormones that only work with auxin receptors. Found in embryos of seeds, young leaves and shoot apex.

• Phototropism
• Stimulation of cell division (in most meristematic tissue)
• Promotion of elongation of cells in shoot apex.
• Differentiation of xylem and phloem
• Development of lateral roots
• Gene expression (activating, inhibiting genes)
• Influences general pattern of development

• Growth in the direction or away from external stimuli (positive or negative)
• What is phototropism?
• In response to light

In response to gravity.

• Auxins are produced on the tip of the stem (shoot apex) but are translocated to areas with less sunlight. Using Auxin Efflux Carriers. (specialized membrane proteins)
• Higher concentrations of auxins on the B side trigger cell elongation and allow for growth in the direction of the sun.
• The binding of auxins to auxin receptor cells produce specific proteins to ensure a faster growth rate on the B side.

The entrance of auxin into the cell. Triggers the production of IAA auxin that stimulate plant growth.

• Auxins bind to auxin receptor cells
• Protopump activates (H ion pumps)
• H ions are pumped to the shady side
• The increase in pH results in the breakdown of cellulose fibers in the cell wall
• Cell wall elongates

Changes the pattern of gene expression through interacting with the repressor of a particular gene.

• Cloning of plants
• If you put meristematic tissue in uygun environment and give it auxin, it will grow into a callus. Gibberellins, cytokinin are used to grow the callus into a plant with a stem + roots.
• Agar Gel
• You can bulk up new species p quickly
• Save the plants from virus
• Rare plants could be reproduced instead of harming ecosystems and taking them from nature.

• Venation:Monocotyledon have parallel venation, dicotyledon have netlike venation pattern in leaves.
• Flower Parts: Three flower parts or multiples of three in monocotyledon, 4 or 5 parts or multiples of four or five in dicotyledon
• Seeds: Monocotyledon only one cotyledon, dicotyledon has two
• Vascular bundles: monocotyledon is arranged all throughout the stem, dicotyledon they’re arranged in a ring
• Root system: monocotyledon is fibrous, dicotyledon has a taproot, main root
• Pollen grain: One opening in monocotyledon, three openings in dicotyledon

Monocots, manglids (magnolias), eudicots (true dicots)

• Anther: part of the stamen that produces male sex cells
• Filament: holds up stamen
• make up stamen
• Stigma: sticky top of the carpel on which the pollen lands
• Style: supports the stigma
• Ovary: base of the carpel where the female sex cells develop
• Make up carpel
• Petals attract pollinators
• Sepal protects buds
• Receptacle is the booty of the plant

• Complete flowers
• Incomplete flowers (lacks at least 1 part like grass)
• Staminate flowers (no carpels just stamens)
• Carpellate flowers (no stamens just carpel)

The process by which pollen (containing male sex cells) is placed on the female stigma

• Cross-pollination (more genetic variety, increased strength, however harder because female stigma might not receive pollen)
• Self Pollination

• They carry pollen
• Wind
• Insects
• Water
• Bird, rats
• Mutualistic relationship to the point of co-evolution between flowers and insects.

A hollow tube that develops from a pollen grain when deposited on the stigma of a flower.

• Happens when female sex cells are fertilized by the pollen to form a zygote.
• Occurs in the ovule of a flower.

• Pollen germinates to produce a pollen tube. The pollen tube grows along the style of the carpel.
• Pollen tube acts as conduits of transport for the male gamete cells from the pollen to the ovule. Within the pollen tube is the nucleus that will produce the sperm.
• The pollen tube completes its growth by entering the bottom of the ovary.
• The sperm moves from the tube to combine with the egg of the ovule to form a zygote.

Yes, it’s actually a double fertilization. After pollination, one of the two sperms produced by the pollen grain combines with the egg. The other combines with two polar nuclei in the ovary to produce a triploid (3n) endosperm.

• Pollen landing on stigma is pollination
• The male gamete fertilizing the ovule is fertilization

• A structure that protects the embryo of the plant
• The seeds will be transported to another location in order to not compete for resources with the parents.

• Dehydration: in order to achieve dormancy
• Dormancy: the seed remains dormant until favorable conditions arise

• Testa: the tough outer coat (outer coat)
• Cotyledons: Seed leaves that function as nutrient storage structures (the meat)
• Hilum: sagdaki cikinti, scar where the seed was attached to ovary
• Micropyle: Scar where the pollen tube entered the ovary
• Embryo root and shoot: become the new plant when germination occurs

Development of the seed to a functional plant

• Optimal temperature
• Water (rehydration of enzymes to break down food stores)
• Oxygen: essential for aerobic respiration

• Imbibition: the absorption of water into the seed
• The water triggers the release of growth hormones gibberellin
• Gibberellin triggers the production of amylase
• The breakdown of starch is stimulated by the cells in the aleurone layer
• Starch is hydrolyzed into maltose
• Maltose is converted into glucose and is transported to the embryo for the radicle (embryo root) and plumule (embryo shoot)

Radicle

• Plumule
• Divided to two
• Epicotyl: above the attachment site of the cotyledon
• Hypocotyl: below the attachment sites of the cotyledon

A change in the expression of genes in the shoot apex

• Plant’s response to light involving the relative lengths of day and light
• Continuous darkness
• Plants are able to detect the presence, direction, wavelength, intensity of light

• Long-day plants
• Short-day plants
• Day-neutral plants

• By PHYTOCHROMES
• So, there are two types of phytochromes:
• Inactive (Pr)
• And active (Pfr)
• Red light converts Pr to Pfr, Pfr can absorb far red lights and rapidly turns back to Pr in daylight. However, in darkness, the conversion is really slow. The buildup of Pfr times the dark period. In long day plants, the remaining Pfr after a short night stimulates flowering. In short day plants, Pfr acts as an inhibitor to flowering.
• Pfr activates certain genes in the shoot apex, resulting in changes in gene expression.

450 (blue) to 600 (red)