Plant PhysiologyPlant Physiology

THE RRR’s Mean Good NewsTHE RRR’s Mean Good News

Plant StylePlant Style

Multicellular, eukaryote, has a cell wall made of cellulose, and has chloroplasts. (autotrophic)

Several types of plants – Bryophytes - Mosses Ferns Conifers - Gymnosperms Flowering Plants - Angiosperms

What makes something a plant?

tracheophytes

How are they classified?

First by structure – bryophyte vs tracheophyte (no veins vs veins)

Then under tracheophoytes they are separated by reproduction – seedless (ferns) – gymnosperms/ conifers – angiosperms

Then under angiosperms you are seperated by monocots and dicots. (This has to do with the structure of how their veins are arranged, number of flower parts, parts of embryo…)

We will focus on angiosperms

These are what we think of when you think of plants.

Roots, stems, leaves

axil - the angle between the upper side of the stem and a leaf, branch, or petiole.axillary bud - a bud that develops in the axil.flower - the reproductive unit of angiosperms.flower stalk - the structure that supports the flower.internode - the area of the stem between any two adjacent nodes.lateral shoot (branch) - an offshoot of the stem of a plant.leaf - an outgrowth of a plant that grows from a node in the stem. Most leaves are flat and contain chloroplasts; their main function is to convert energy from sunlight into chemical energy (food) through photosynthesis.node - the part of the stem of a plant from which a leaf, branch, or aerial root grows; each plant has many nodes. Label the two lower nodes (the first and second nodes) on the plant diagram.petiole - a leaf stalk; it attaches the leaf to the plant.root - a root is a plant structure that obtains food and water from the soil, stores energy, and provides support for the plant. Most roots grow underground.root cap - a structure at the ends (tips) of the roots. It covers and protects the apical meristem (the actively growing region) of the root.stem - (also called the axis) is the main support of the plant.tap root - the main root of some plants; the tap root extends straight down under the plant.terminal bud - a bud located at the apex (tip) of the stem. Terminal buds have special tissue, called apical meristem, consisting of cells that can divide indefinitely.

Transport

Definition: How do plants move their materials? IN VASCULAR PLANTS – the transport

system is made up of two types of tubes - strong, thick pipes called xylem vessels, and thinner tubes called phloem vessels. The cells of these vessels are modified to make them suited to performing their special functions.

Transport Tubes

Xylem consists of dead cells with no end walls, which contain lignin to form stiff tubes. They are impermeable, and are strengthened with fibres.

Phloem consists of living cells lined with cytoplasm, with walls made of cellulose and perforated end walls called sieve plates. They are permeable, and are surrounded by companion cells.

monocot dicot

Transport

How does water move through the xylem? This is a combination of root pressure, capillary

action, and transpiration. Capillary action – water is attracted to itself and to the

sides of the tube (graduated cylinder – meniscus) (remember cohesion and adhesion)

Transpiration – like plant sweating – this is water evaporation out of the openings in the leaves – so that evaporation pulls the water up. To control transpiration a plant uses guard cells to open and close it’s stomates

Homeostasis

Remember – all parts of a multicellular organisms

Excretion

Getting rid of metabolic wastes… Wastes a plant make?

O2 – this is excreted through the stomates (controlled by the guard cells)

Water – again excreted through the stomates

Respiration Exchange of gases with the environment Plants take in CO2 and let out O2 However they do use some of their O2 for

cellular respiration, and the waste CO2 for photosynthesis. However, it is not enough to keep the plant alive.

Plants keep their stomate open just enough to allow photosynthesis to take place, but not so much that they lose an excessive amount of water.

Regulation

Responding to the environment… So are plants able to respond to the

environment? They use Tropisms and hormones

Tropisms – Indicates growth or turning movement of a biological organism in response to an environmental stimulus. Phototropism – movement is response to lights or colors

of lights. Geotropism/ gravitropism – movement in response to

gravity

Tropisms/ Hormones

Hydrotropisms – movement in response to moisture or water

Thigmotropism – movement in response to touch or contact (memosa plant – venus fly trap – this is also how vines grow up the side of buildings)

Hormones

AUXINS – plant hormones For plant growth, cell differentiation, mediates tropistic

response for gravity and light, fruit ripening, stimulates flowering, etc

Cytokines Stimulates cell division, stomate opening for some species,

shoot and bud formation Gibberellins

Stimulates stem elongation by stimulating cell division, breaks seed dormancy, enzyme production, causes seedless fruit development

Reproduction

Asexual Vegetative propagation – undifferentiated tissue

(meristem) in plants provides a source of cells from which a new plant can develop (natural occurring) Bulbs - parts of a root that split to form several new bulbs Tubers – modified underground stems that have buds (like

potatoes) Runners – plant stem that run above and along the ground,

that produce new roots Rhizomes- woody underground stems that appear at

intervals (iris/ ginger)

Artificial reproduction

Cutting – when cut, a piece of stem of some plants will develop new roots in water

Layering – the stems of certain plants, when bent into the ground and covered by soil, will take root. (blackberry and raspberry bushes)

Grafting – the stem of one plant is attached to the rooted stem of another closely related plant. No mixing of hereditary characteristics occur they remain genetically destinct

Sexual reproduction in angiosperms The Flower – the sex organ which consists of

both male and female parts. Female organ is the Pistil

Consists of the stigma Style Ovary – produces haploid ovum

The male organ is the Stamen Anther – thin stalk like filament produces haploid spores

called pollen

Flowers

The petals are specialized leaves that surround and protect the pistil – They attract insects with their characteristic colors and odors.

Some plants have only male parts, some have only female parts, and some have both for cross pollination

Epicotyl (will become the shoot-stems and leaves)

Radicle (embryonic root) Hypocotyl (connection between cotyledon

and radicle) Cotyledon (seed leaf) Note: If the seed has one cotyledon, it is a

monocot. Corn is a monocot. If it has two, it is a dicot. A bean is a dicot.