Plant Cells, Tissues, and Organs

Plant Organ Systems A plant has two organ systems: a shoot system and a root system. The shoot system is everything that is above ground: the stem, leaves, buds, flowers, and fruits. The root system is everything underground, as well as aerial roots.

The Shoot System The functions of the shoot system include Photosynthesis, Reproduction, Storage, Transport, Hormone production.

What is Photosynthesis? The word photosynthesis can be separated to make two smaller words: “photo” which means light “synthesis” which means putting together Photosynthesis is the process by which plants make their own food.

How does it make food? To make food plants need: carbon dioxide water sunlight Carbon dioxide from the air passes through small pores (holes) in the leaves. These pores are called stomata. Water is absorbed by the roots and passes through vessels in the stem on its way to the leaves. Sunlight is absorbed by a green chemical in the leaves.

The Process of Photosynthesis Photosynthesis takes place in the leaves of plants. The leaves are made up of very small cells. Inside these cells are tiny structures called chloroplasts. Each chloroplast contains a green chemical called chlorophyll which gives leaves their green color. Chlorophyll absorbs the sun’s energy. It is this energy that is used to split water molecules into hydrogen and oxygen. Oxygen is released from the leaves into the atmosphere. Hydrogen and carbon dioxide are used to form glucose or food for plants.

The Leaf Its most important job is to provide a large surface area for photosynthesis to take place Upper surface Made of a layer of dermal tissue called the epidermis Epidermal cells secrete a waxy cuticle (top layer) that: helps reduce water evaporation off of leaf protects the leaf so it can perform its primary function, photosynthesis sunlight passes through epidermal cells to photosynthesizing cells

Lower surface (underside) Guard cells allow gases to move in & out of the leaf these cells have special pores called stomata transpiration happens through these pores CO2 enters, H2O and O2 leave transpiration = evaporation of water from the leaves

The Stem Has 2 main jobs: Xylem & phloem tissues are found here support transportation of water, nutrients and sugars Xylem & phloem tissues are found here Both are made of vertically stacked tubes Most of a plant’s xylem tissue is found in the stem when xylem cells die, they provide long, fibrous ‘pipes’ that allow water to be transported easily Phloem’s cell walls are porous to allow materials to move easily between phloem & neighbouring cells Xylem & phloem are grouped together in vascular bundles

Plant Body Stem: series of nodes and internodes Functions Holds leaves up to light Transports substances through vascular tissue Phloem transports sugar throughout Xylem conducts water and minerals up from roots

Plant Body Root Functions Anchors plant in soil Takes up water and minerals from soil

The Roots Also has 2 main jobs: anchor the plant to the ground allow for water and minerals to be taken out of the soil In some plants, the roots act like a storage area for starch & minerals Special cells in the roots called cortex cells serve to store starch (long chains of glucose) Endodermis tissue controls water and mineral flow to vascular tissues Pericycle tissue surrounds the xylem and phloem it allows roots to branch out

Cross section of an Actual Root

Types of Roots 1. Taproot One main root that grows larger and thicker than the rest Allows plant to reach far underground for water ex: dandelion, thistle 2. Fibrous root Thin, hair-like roots Allows plant to absorb water from near the surface of the soil Help prevent erosion ex: grass, yarrow

The Root System Two primary root system types: Taproot system - Single primary root dominates over branch roots ( usually found in Gymnosperms and most Dicotyledons)

The Root System Two primary root system types: Fibrous root system – A network of fine roots with no central dominant root. Fibrous root systems don't go as deep as taproots, but they spread laterally

Meristematic Cells form Tissues Types of plant tissues: 1. Dermal tissue 2. Ground tissue 3. Vascular tissue

Three Types of Plant Tissues Vascular Tissue Transport Support Ground Tissue Synthesis of Sugars Storage Dermal Tissue Protection

Types of Plant Tissues 1. Dermal tissue  outermost part Made of epidermal cells These cells act as a barrier by: protecting the more delicate inner tissues controlling the exchange of materials 2. Ground tissue  middle layer Made of photosynthesizing cells & support cells 3. Vascular tissue  innermost tissue Xylem tissue transports water and dissolved minerals to the leaves, and phloem tissue conducts food from the leaves to all parts of the plant.

REPRODUCTION in Flowering Plants

I. FLOWERS Flowers are the organs of reproduction in flowering plants

Flowering Plant Reproduction Pollen grains Ovule Flower Meiosis Mitosis Flowers are modified leaves, specialized for reproduction. Flower parts undergo meiosis to produce haploid products pollen grain ovule (contains egg cell)

Angiosperms (flowering plants) Plants that protect their seeds within the body of a fruit. Make up ¾’s of all plants, including: Trees, shrubs, herbs, grasses, water plants…

PARTS of the flower include: Sepals: enclose the flower bud and protect it until it opens Petals: attract pollinators

More flower parts- Pistil: female reproductive organ; ovules contain the female gametophyte generation, located inside the ovary at the base of the pistil Stamen: male reproductive organ, pollen grains contain male gametes and form inside the anther

Male Reproductive Structure The stamen consists of two parts: Anther and Filament The anther is where meiosis occurs to produce haploid pollen-the male reproductive cell The filament is a stalk that supports (holds) the anther

Female Reproductive Structure The pistil aka Carpel - consists of the stigma, style and ovary and ovule The sticky stigma receives the pollen during fertilization The pollen goes down a tube (style) from the stigma to the ovary

Female Reproductive Structure The ovary, the femal reproductive organ where ovules are produced. Ovules are the female reproductive egg – turns into a seed when fertilized by pollen

Ovary Each ovule within an ovary has a micropyle (an opening for the pollen tube). The ovules’ megasporangium undergo meiosis to produce four haploid cells (3 die leaving 1 megaspore) The megaspore undergoes mitosis 3 times to produce 8 haploid cells within the embryo sac.

Reproductive Structures Petals: colourful structures that attract pollinators. Sepals: surround and protect the flower bud.

Pollination Wind, insects or other animals transfer pollen from the anther of one flower to the stigma of another Flowers vary depending on pollination mechanism

Fertilization After pollen lands on the stigma, a pollen tube grows down through the style to ovary Generative cell creates the two sperm nuclei Double fertilization occurs: one sperm fertilizes the egg one sperm the two polar nuclei together

Result of Double Fertilization The sperm nucleus and egg nucleus join to form a 2n (diploid) embryo The other sperm nucleus and the two polar nuclei join to form a 3n (triploid) endosperm. The endosperm is the food supply for the embryo. First link

Seed and Fruit Development After fertilization, the petals and sepals fall off flower Ovary “ripens” into a fruit The ovule develops into a seed

Pollination and Fertilization in a Flower Mature Pollen Grain Sperm Cells Tube Cell Nucleus 1. pollen grains land on stigma 2. pollen tubes grow down stigma to ovary 3B: Fusion of 2nd sperm + two polar nuclei Stigma 3. double fertilization Style Sperm 3A: Fusion of sperm + egg Pollination and Fertilization in a Flower Ovule Polar nuclei Ovary Egg