Plant cells – the basic building blocks • each cell is approximately 1/10- 1/100th of a millimeter long • cells can specialize in form and function

Plant cells vs. Animal cells • In addition to a cell membrane, plants have cell walls made of tough compounds (cellulose and lignin) which makes them rigid • Plant cells have an organelle called the chloroplast, which allows plants to photosynthesize • Chloroplast is where the plant gains its energy

Plant Body Organization (pictured above) Organs  Tissues  Cells

Major Organs  roots, stems, leaves

Tissues - a collection of similar cells that serve a specific purpose by functioning together

• Some tissues have specialized cells

• Tissues arrangement can vary based on type of plant Monocot (contains a Pith ) vs Dicot

There are 3 types of tissues • Ground tissues – metabolism, storage, and support activities o the ground tissue of the leaf (called mesophyll) uses the energy in sunlight to synthesize sugars in a process known as photosynthesis o the ground tissue of the stem (called pith and cortex) develops support cells to hold the young plant upright o the ground tissue of the root (also called cortex) often stores energy- rich carbohydrates Ex. Parenchyma, Sclerenchyma

• Vascular tissue - helpful for the movement of water, nutrients etc. o Vascular plants have xylem and phloem as part of their vascular system o xylem – carries and distributes water o phloem – carries and distributes sugars / nutrients Ex. Tracheids and vessel elements, companion cells

• Dermal tissues – the exchange of matter between the plant and the environment (CO2 & O2) o epidermis on above ground organs (leaves and stems) is involved with gas exchange o the epidermis on below ground organs (roots) is involved with water and ion uptake Ex. Epidermal cells, stomata

Below is a summary chart of the 3 types of ground types:

1. Collenchyma – long & thick cell cells, under epidermis, flexible

2. Parenchyma – spherical, thin walled, throughout the plant  photosynthesis, respiration , and regeneration

3. Sclerenchyma – secondary walled composed of lignin, fibre in wood/bark/fruits and seeds, provide structural support where growth has stopped

   PARENCHYMA COLLENCHYMA SCHLERENCHYMA Characteristics • Spherical • Thin-walled • Living, metabolizing tissue • Elongate cells with unevenly thickened cell walls • Alive at maturity • Secondary cell walls composed of lignin • Dead at functional maturity Location • Throughout the plant • Beneath the epidermis in young stems and in leaf veins • Fibres in wood, bark, stems • Fruits and seeds Functions • Photosynthesis and respiration • Storage in roots • regeneration • Flexible support system in areas of active growth • Structural support where growth has ceased (Pictured is the cross section of a leaf) Plant organs: tissues that act together to serve specific functions for the whole plant

Roots • Root functions : o To anchor o Absorb water and dissolve mineralso Storage (of excess sugars ) o Conduction

• Root Anatomy: o Epidermis – single layer of cells for protection and absorption o Short livedo Root hairs – increase surface area is great to allow for more absorption of water throughout soil o Cortex – storage of starch and contain air spaces for aeration of the root cells o Pericycle – a layer of cells that surrounds vascular tissue in stems and roots. o Casparian Strip - a band-like thickening in the center of the root endodermis of vascular plants. Made of mainly lignin. Makes a barrier between cells important for selective nutrient uptake / to exclude pathogens

• Vascular Tissue: Xylem o Water Moves VERY FAST in xylem ( ~2 ft/ minute) o Conducts water and dissolved minerals o Made of:  Vessels – tube like structures, with hollow long cells  dead cells  Tracheids – water-conducting cell in the xylem that provide mechanical support  Xylem parenchyma – living parenchyma cells, structural component, and stores food  Xylem fibres – separated by thin cross walls o Upward movement caused by transpiration from leaves caused by water properties: polarity of H2O, cohesion, and adhesion

Cohesion – ability of water to stick to itself and move up the plant from the roots Adhesion – ability of water to stick to xylem cell walls

• Vascular Tissue: Phloem o Moves food (sugar and amino acids) from leaves storage o Phloem made of sieve elements (sieve tube members, companion cells)  Sieve tube is a series of sieve tube members arranged end-to-end and interconnected by sieve plates  Movement of sugars up or down through plasmodesmata of sieve elements o One inch/ minute

• Companion Cells o Modified parenchyma cells – preform cellular functions of sieve tubes o Many plasmodesmata – allow transfer of sucrose containing sap over large area

• Sieve Tubes: o Sieve tube elements are long + contain cellulose cell walls. Transfer over LARGE areas o Living cells WITHOUT nucleus or organelles – makes more space to transport sap BUT explains why sieve elements NEED companion cells to carry out cellular functions

Stems • Support leaves and fruit • Conduct water and sugars

Tissues of stem  Epidermis – protection & cuticle to save moisture  Cortex – Store food, support cells & photosynthesis  Xylem – Conduction of water and minerals & contains strong supporting fibers  Phloem – conduction of food & support Leaves Main organs of photosynthesis Carbon dioxide & water  sugar + oxygen

Major tissues of the leaf

Epidermis  Transparent- light goes right through (a) Main function - protects against drying out (cuticle) (b) Stomata with guard cells  Function- gas exchange, especially common on lower epidermis

Mesophyll  Site of photosynthesis  Air spaces between cells for gas exchange to each cell

Veins  Xylem- water conduction  Phloem- food conduction  Bundle sheath- one or more layers of fiber cells surrounding a vein; strengthens vein to support leaf  Branching extensive in veins- no mesophyll cell is far from a vein

Monocots  one cotyledon, veins are typically parallel, fibrous root system, floral parts in multiples of three

Dicots  two cotyledons, veins usually netlike, vascular bundles arranged in a ring, taproot usually present, floral parts usually in multiples of five

Plant physiology – how they all work together

Transportation in plants Transportation in plants refers to the movement of water and minerals from the roots to different parts of the plants. It also includes the movement of the sugars produced by the leaves to the entire plant.

Transportation occurs in three levels in the case of plants: • Transportation of substance from one cell to another. • Long distance transport of sap within phloem and xylem. • The release and uptake of solute and water by individual cells.

Water is absorbed in plants in 2 ways:

Active Absorption – slow • water moves through symplast, and it is absorbed according to the Diffusion Pressure Deficit changes • It consists of osmotic and non-osmotic forces. • The force required for the absorption of water is mainly generated in the root cells

Passive Absorption – fast • occurs in rapidly transpiring plants. • rate of absorption significantly depends upon the rate of transpiration. • The force required for the absorption of water is mainly generated in the mesophyll cells.

Transportation in plants is by 3 means • Diffusion - passive movement of a substance from cell-to-cell or from one plant part to the cell o slow o does not require energy o Substance moves from higher concentration region to lower concentration region.

• Facilitated diffusion o is a passive process o Consists of antiport, uniport, and symport. o Uniport protein is to carry single solute across the membrane. o Symport proteins transfer two different solutes simultaneously in the same direction. o Antiport proteins exchange the solutes by transporting them in and out of the cell.

• Active Transport o Active transport pumps molecules against the concentration gradient. o the energy of ATP is used to drive the pump. (ATP donates a phosphate to a particular gateway molecule which then pumps the desired molecule across the membrane)

Driving forces of transportation: • Transpiration • Force of surface tension • Water potential gradients (build up) • Force of hydrogen bonding

Water and ion transport pathway • Water is needed in leaves but only available in soil. THUS, Water and ion uptake occurs at the root hairs. • The Casparian bands in the endodermis (the innermost layer of the cortex) function as an impermeable barrier, which allows the endodermis to selectively absorb desirable ions (e.g., K, Ca, PO4 , NO3, Cl) and block undesirable ions (Na, Al). • The water and absorbed ions diffuse into the hollow water-conducting cells (tracheids and/or vessels) in the root xylem to the stem and leaf • The water and ions move from the xylem into the mesophyll of the leaf. • water not needed evaporates from the surface of small pores called stomates in the leaf epidermis via a process called transpiration.

How does water move up the plant ? • In essence, water moves via the same mechanism as drinking from a straw • In very thin channels like the water-conducting cells, the water molecules have great cohesive force, meaning that they cling very tightly to each other. • Like a lengthy chain extending all the way back to the roots, each water molecule pulls up the molecule below it, and so the whole water column moves up the plant.

• The rate of water movement depends on the rate of water evaporation (transpiration) at the stomates.

How do solutes move through a plant ? • Sugars are made in leaves through photosynthesis, but must be moved to other parts of the plant • Sugar diffuses from the mesophyll in the leaf  the phloem cells in the vascular bundles. • Specialized companion cells load the dissolved sugar into the sugar-conducting cells (sieve elements) of the phloem by using ATP (note: sieve cells so not have nucleases) o Since the high concentration of dissolved sugar dilutes the water in the conducting cells, more water molecules diffuse via osmosis from the intercellular spaces (with high water concentration) around the vascular bundles into the sugar conducting cells (with low water concentration). • This osmotic water flow generates a high hydraulic pressure that moves the dissolved sugar solution through the phloem conducting cells from the leaves to the rest of the plant where the sugar is unloaded by other companion cells.

Tendril – a lateral organ that can encircle an object when encountered • Threadlike strand, produced usually from the node of a stem