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Introduction to Plant Science

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Introduction to Horticulture By Carrie Carson. The Importance of Plants Without plants, life on earth could not exist Plants are the primary source of.

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1 Introduction to Plant Science

2 The Importance of Plants
Without plants, life on earth could not exist Plants are the primary source of food for humans and animals

3 The Importance of Plants cont.
Plants also: Provide oxygen Provide shade Supply us with medicines Renew the air Slow down the wind Hold soil in place Are a home for wildlife Furnish building materials and fuel

4 Parts of the Plant Most plants are made up of four basic parts: Leaves
Stems Roots Flowers (these later become fruit or seeds)

5 Leaves Are the food factory of the plant
They produce all of the food that is used by the plant and stored for later use by the plant or by animals

6 Leaves Come in All Shapes and Sizes!
Needles are actually very narrow leaves The thorns on a cactus are leaves Some leaves are flat Other leaves, like onion leaves, are cylindrical The shape and size of leaves helps to identify plants



9 Leaf Arrangement Leaves are arranged in many different patterns and positions: Alternate Opposite Whorled Simple Pinnate Bi-Pinnate Palmate

10 Leaves on the Outside Parts: - Petiole - Blade - Vein
- Midrib - Margin Tip Margin Midrib

11 Leaf Parts cont. Petiole - leaf stalk
Blade - the larger, usually flat part of the leaf Midrib - large central vein from which all other leaf veins extend Veins - form the structural framework Margins - edges of plant leaves

12 Leaves on the Inside Leaves have specialized cells that perform very important, very specific tasks.

13 Leaf Cells Epidermis - skin of the leaf Single layer of cells

14 Leaf Cells cont. Chloroplasts Photosynthesis Food making cells
Chlorophyll - green color Photosynthesis Process by which chloroplasts make food The oxygen created is used directly by people and animals Without O2 there would be no burning, rusting, or rotting

15 6H2O + 6CO2 ----------> C6H12O6+ 6O2
Photosynthesis LIGHT 6H2O + 6CO > C6H12O6+ 6O2 CHLOROPHYLL Six molecules of water plus six molecules of carbon dioxide, in the presence of light and chlorophyll, produce one molecule of sugar plus six molecules of oxygen

16 Plant Food Food made in the leaves moves down the stem to the roots
It is then used by the plant or stored in the roots or stem as sugar, starch, or protein The plant is also used as food for people and animals The leaves are usually the most nutritious part

17 Respiration Plants breathe 24/7 They consume O2 and release CO2
Roots, stems, and leaves all need O2 to grow Plants produce more O2 during photosynthesis than they consume while breathing

18 Stems Stems have 2 main functions: The movement of materials
Movement of water and minerals from roots up towards the leaves Movement of manufactured food from the leaves down to the roots Support of the leaves and reproductive structures Flowers and fruit or seeds

19 Stems cont. Stems are also used for: Food storage Reproductive methods
Irish Potato Reproductive methods Stem cuttings or grafting Green stems manufacture food just like leaves

20 Stems on the Outside Lenticels Breathing pores

21 Stems on the Outside cont.
Bud scale scars Indicate where a terminal bud has been located The distance between two scars represents one year of growth Leaf scars Show where leaves were attached

22 Unique Stems Irish Potato & Gladiolus Very different stems
Stems are used for food storage and plant reproduction                             

23 Stems on the Inside In all stems:
Water and minerals travel up the XYLEM Manufactured food travels down the PHLOEM

24 Dicots Dicots (2 cotyledons) the xylem and phloem are separated by the cambium The cambium produces new cells Grow continually because the cambium builds new xylem and phloem cells Trees are a perfect example! Sap = new xylem Heartwood = old, inactive xylem Tree bark = old, inactive phloem


26 Monocots One cotyledon (seed leaf) Grasses, corn No outside cambium
Vascular bundles that contain xylem & phloem Cells don’t increase in number, they grow in size (won’t keep growing like a tree)


28 Monocots vs. Dicots

29 What do we do with Stems? Food Building Materials Asparagus
Irish Potato Celery Building Materials Wood

30 Roots Usually underground – not visible Functions:
Anchor the plant and hold it upright* Absorb water and minerals from the soil & conduct them to the stem* Store large quantities of plant food* Propagate or reproduce in some plants * = essential to all plants

31 Roots on the Inside Very similar to a stem
Older roots of shrubs & trees have: Phloem on the outside (old phloem is bark) Cambium layer Xylem (wood) on the inside

32 Phloem Carries manufactured food down to the root for food storage Xylem Carries water and minerals up to the stem

33 Roots on the Outside Different from a stem On a stem, the terminal bud
initiates growth On a root, the root cap Root cap continuously makes new cells that protect the root as it pushes into the soil

34 Root External Structure
Behind the root cap are root hairs Root hairs become side roots that branch out as the root grows older Absorb moisture and minerals which are conducted up to the larger roots and the stem

35 Roots as Crops Cash crops Carrots Beets Radishes Sweet Potatoes
Sugar Beets - Sugar Radishes Sweet Potatoes

36 Root Propagation Plants with tuberous roots:
Dahlia Peony Sweet Potato Are propagated by separating the root clump or by rooting spouts from the root

37 Types of Root Systems Fibrous Root System vs. Tap Root System

38 Which root system is easier to transplant? Fibrous roots or tap roots?
Answer: Fibrous roots Why? Because when plants are dug up out of the ground, a greater % of the fibrous roots system is saved.

39 If a root loses to many root hairs while being transplanted, the plant will die.
Larger roots only conduct & store water, nutrients, and food Root hairs absorb moisture from the ground

40 Flowers, Fruits, & Seeds Flowers are pretty & contain nectar in order to attract insects These insects fertilize the flower by pollination Pollination begins fruit and seed formation                                 

41 Fruits & Seeds Fruits and seeds are eaten, collected, and spread out by animals and people This reproduces the plant

42 Seeds Seeds have special devices to ensure propagation
Some seeds are sticky (thistles), some float in the wind (dandelions), others can survive stomach acid (cherry pits)

43 Flower Parts Flowers differ in shape, size, and color, but all have relatively the same parts

44 Flower Parts cont. Seeds are the most common way plants reproduce in nature Sexual process involving male and female parents A complete flower has both male and female parts Only one parent is needed if a plant is self-fruitful, or can pollinate itself

45 Flower Parts cont. 4 main parts Sepals Petals Stamens Pistil

46 The Sepals Green, leaf like parts of the flower that cover and protect the flower bud before it is open

47 Petals Are actually leaves
Generally the most striking part of the flower Bright colors are used to attract insects for pollination

48 The Stamens Male reproductive part Each stamen consists of: Filament
Anther – contains the pollen (male sex cell)

49 The Pistil Located in the center of the flower Female part
Produces female sex cells (eggs or ovules) If fertilized, the eggs become seeds

50 Parts of the Pistil 3 main parts: Stigma – sticky, catches the pollen
Style – tube that leads to the ovary Ovary – eggs develop here, after fertilization the ovary grows to become a fruit or seed coat


52 Flower Construction Insects looking for nectar have to climb over the anther and brush pollen on their legs As they climb towards the center looking for food, they deposit pollen on the stigma

53 Fertilization After an insect deposits pollen, fertilization begins!
The pollen grain sprouts and sends a long stalk (pollen tube) down the style to the ovary

54 Fertilization cont. The pollen sperm cell can then fertilize the female egg cells and seeds begin to develop The ovary enlarges into a seed coat or fruit

55 Pollen

56 Incomplete Flower Has ONLY male parts or female parts
Male flower – sepals, petals & stamens but no pistil Female flower – sepals, petals, & pistil, but no stamens Examples: Kiwi, Ginkgo

57 Flowers are Important! Many plants are grown only for their flowers
Floriculture industry in a multimillion dollar business!!!

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