1
Materials for lab
Bring a digital camera if you have one available
Teaching Objectives
Plant diversity: Applications and importance
Plant form and function: Plant survival and human use
Local and global examples of terrestrial plant types
Student Learning Objectives
(1) View the plant diversity at Ho'omaluhia Botanical Garden
(2) Know how to access information regarding plant identification
(3) Be aware of differences between mosses, ferns, and flowering plants
INTRODUCTION
Plants are the producers in a food web. Solar energy is stored in the chemical bonds of the sugars produced by plant photosynthesis, the biochemical process by which plants utilize light energy from the sun to produce sugar from carbon dioxide and water. Consumers in a food web derive their energy by breaking down these bonds during respiration, which releases the stored energy. Energy flowing within the food web therefore enters it by way of plant photosynthesis.
The importance of plants to the survival of humans and other animals cannot be over-emphasized. Our basic needs of oxygen, food, shelter, and clothing are provided, directly or indirectly, by plants.
Because plants absorb carbon dioxide and release oxygen in photosynthesis, they may be a significant factor in reducing the
"greenhouse effect", which is caused by human activities that increase the carbon dioxide in the atmosphere. Deforestation and the burning of fossil fuels (oil, coal, and gas) are two examples of such activities.
There are about 235,000 species of flowering plants in existence today. Approximately a third of these are native to temperate regions, and the remainder are found in the tropics. A vast number of tropical plants are in danger of extinction in the wild within the next hundred years because the human populations of most tropical countries continue to double every 20 to 25 years, and because the forests are rapidly being cleared for wood and cultivation. More than half of the world's tropical forests have already been cleared, and experts predict that most of what is left will be gone in less than 50 years. With them will vanish a quarter of all life-forms including, perhaps, a plant that could provide a cure for cancer or help end world hunger.
So little is known of the plants of the tropics that many have not even been given scientific names. Preserved samples of these plants may well be all that are passed on to our descendants in the 21Stcentury and beyond. The useful properties these plants possess can certainly be determined better today, when species are still in existence, than at any point in the future.
This week's lab is designed to introduce you to the incredible diversity within the plant kingdom, to note some of the purposes for which plants have been utilized by humans, and to help you appreciate the forms into which they have been modified and shaped by evolution.
We will look at examples of several types of terrestrial plants: ferns, conifers, and flowering plants. The emphasis will be on form and function, from the perspective of both plant survival and human utility.
PLANT DIVERSITY
Terrestrial (land-dwelling) plants can be separated into four major groups based on their anatomy, reproduction, and life cycle. These four groups are mosses, ferns, gymnosperms, and flowering plants.
Mosses are non-flowering terrestrial plants that reproduce by spores. Mosses don't have vascular tissue (analogous to human veins) to distribute water within their bodies. Instead, they absorb water through pores located on all parts of the plant body. Since mosses lack veins, they are small in size and close to the ground where moisture is readily available.
Ferns are non-flowering plants that also reproduce by spores but that have vascular tissue to distribute nutrients and water to all portions of the plant body. Since ferns have veins, they can grow taller than mosses.
Gymnosperms are non-flowering plants that reproduce new plants with seeds. You probably remember from your previous work on seed germination that a seed contains the embryo of a young plant, in addition to nutritive tissue and a protective outer tissue called the seed coat. The largest group of gymnosperms, called conifers, produce their seeds in cones.
Flowering plants, more technically called angiosperms, are the most successful, diverse, and widespread of the land plant groups. Flowering plants range in size from tiny duckweed, a few millimeters in size, to Eucalyptus trees more than 100 meters (328 ft.) in height. There are even flowering plants that have invaded the oceans where they produce flowers underwater.
PLANT ORGANS
Just as your body has separate organs to carry out special functions (e.g., heart, lungs, stomach), so, too, are plant tissues organized into organs that carry out specific functions.
Plant Parts
Plants have three vegetative organs: roots, stems, and leaves.
Leaves are the major photosynthetic organs, which make all the food for the plant. They do this by changing light, water and gases into food. This process is called photosynthesis.
Shoot System: Stems and branches support the photosynthetic organs and serve as a conduit for water and nutrients between the roots and leaves. Some plants have stems modified for storage of water or carbohydrates, or for asexual propagation.
Roots are generally used to anchor the plant in the soil and to absorb water and nutrients from the soil.
Flowersare the reproductive organs of angiosperms.
The ovary, or female reproductive organ of a flower, develops into a fruit after fertilization by the male pollen.
The seeds produced by the plant are enclosed in the fruits. Most people are familiar with large, colorful flowers such as hibiscus, plumeria, orchids, and lilies.
Roots
All roots are responsible for:
- anchoring the plant to the ground
- extracting water and minerals from the soil
In a typical root we can distinguish the following parts:
1. Primary root - the thickest . It grows downwards.
2. Secondary roots - arise from the primary root. They are not as thick as the primary one. They go sidewards.
3. Root cap - is a kind of protection the roots end with. It is designed to drill the soil and it is able to guide the root growth by perceiving gravity.
4. Root hairs - are minute filaments roots are covered with. They absorb water and nutrients from the soil.
Stems
All stems are responsible for:
- supporting leaves and flowers physically
- holding the leaves and flowers in the best position for food gathering and reproduction
- transporting materials using xylem and phloem to areas of plenty to areas of need in various parts of the plant
- storing nutrients for future use
bud - an underdeveloped and unelongated stem composed of a short axis with compressed internodes, a meristematic apex, and primordial leaves and/or flowers.
terminal bud - a bud at the tip of a stem responsible for terminal growth.
axillary bud or lateral bud - buds along side the axis of a stem; they were produced by the terminal bud during growth; once they grow out and form a lateral stem they become terminal buds of the lateral branch.
flower bud - a bud containing a floral meristem which develops into flowers; usually larger than vegetative buds.
leaf scar - a scar marking the former point of attachment of a leaf or petiole to the stem.
internode - the part of the stem between nodes
node - part of stem marking the point of attachment of leaves, flowers, fruits, buds and other stems.
lenticel - rough areas on stems (and some fruits, ex. apple) composed of loosely packed cells extending from the cortex through the ruptured epidermis; serve as "breathing pores" for gas exchange. Only occur on young stems.
growth rings - bud scale scars from the last terminal bud; they denote flushes of growth (usually per year). Can be used to age stems because usually 1 set of growth rings is produced per year on temperate trees in the Temperate Climatic Zone.
Leaves
All leaves are responsible for:
- absorbing the sun's rays
- the majority of photosynthetic production (which can take place in any green part of a plant),
- taking in carbon dioxide and releasing oxygen and water vapor (breathing)
- removing waste products from the plant
- using osmotic pressure to draw water up from the roots
Parts of a leaf
tip / the terminal point of the leafblade or lamina / the flattened, green, expanded portion of a leaf.
margin / edge of a leaf.
midrib / the most prominent central vein in a leaf.
lateral veins / secondary veins in a leaf.
petiole / the leaf stalk (connects blade to stem).
stipules / leaf-like appendages (at the base of petiole of some leaves).
Basic leaf shapes
Sword-shaped
(ensiformis)
Long, thin,
pointed /
Lance-shaped
(lanceolata)
Long, wider
in the middle /
Ovate
(ovata)
Oval, with a
tapering point /
Elliptic
(elliptica)
Oval, with a
short point /
Round
(rotundifolia)
Circular /
Cordate
(cordata)
Heart-shaped
Oblanceolate
(oblanceolata)
Top wider than
bottom /
Spathulate
(spathulata)
Spoon-
shaped /
Rhomboid
(rhomboidalis)
Diamond-
shaped /
Lobed
(lobata)
With several
points /
Spear-shaped
(hastata)
Pointed,
with barbs /
Pinnatisect
(pinnatifida)
Cut, but not to
the midrib
Pinnate
(pinnata)
2 rows of
leaflets /
Bipinnate
(bipinnata)
Each leaflet
also pinnate /
Tripinnate
(tripinnata)
Each leaflet
divided into 3 /
Trifoliate
(trifoliata)
Divided into
3 leaflets /
Palmate
(palmata)
Divided into
many lobes /
Digitate
(digitata)
Divided into
5 lobes
Opposite
(oppositifolia)
Leaves opposite
one another /
Alternate
(alternifolia)
Arranged
alternately /
Perfoliate
(perfoliata)
Stem through
the leaves /
Peltate
(peltata)
Rounded,
stem underneath /
Whorled
In circles
round the stem /
Rosette
Leaves in
close rings
Fruit and Seeds
The fruit is that part of a plant which is in charge of protecting the seeds and guarantee their dispersal. It becomes as a result of the fertilization inside the carpel, which produce the ripening of the ovary walls that will create the fruit. Some fruits, however, have another origin, deriving from the flower receptacle or some other parts of the flower.
We have many kinds of fruits but the most typical fruit shows the following parts:
The pericarp is the external part of a fruit. It is all that surrounds the seed. It is divided into:
The exocarp is the outer covering. In an apple, for instance, it is what we know as the "skin".
The mesocarp is the middle covering. In a peach what we ordinary call the "flesh".
The endocarp is the inner covering , in many cases the stiffened part normally covering the seed. In a plum , for example, what we commonly know as the "stone".
Seeds
The seed is enclosed inside the endocarp. This is a typical seed. We can see the following parts:
The radicle is the part of the embryo which emerges first. Once outside it develops into a main root, producing root hairs and secondary roots.
- The plumule is like a leaf in its early development.
- The hypocotyl is the space between the radicle and the plumule. It develops into a stem.
The endosperm is the food supply contained in the seed. This is sometimes included in the cotyledons, which either achieve the function of primary leaves or food storage, even both of them in some cases.
According to the number of cotyledons, we classify plants in two groups: monocotyledons or monocots and dicotyledons or dicots. In the first group we find so important plants as cereals, palms, lilies, tulips or orchids. The members of the second group are more numerous and comprises most of the trees and flowers.
The seed coat or testa - is the outer layer of the seed.
The micropyle is a litle pore on the seed coat , through which, apart from entering the sperm, the seed absorbs water to begin germination.
FLESHY FRUITSformed from a single flower
/ Berry
A Berry is a single fleshy fruit without a stone, usually containing a number of seeds.
This is a Kiwi Fruit (Actinidia chinensis). Other fruits of this type are: Banana (Musa), Coffee (Coffea arabica), Currant (Ribes), Pasionfruit (Passiflora), Pepper (Capsicum), Tomato (Lycopersicon esculentus).
/
Drupe
A Drupe is a single fleshy fruit with a hard stone which contains the single seed.
This is a Cherry (Prunus avium). Other fruits of this type are: Apricot (Prunus armeniaca), Plum (Prunus x domestica), Coconut (Cocos nucifera), Olive (Olea europaea), Peach (Prunus persica), Sloe (Prunus spinosa).
/
Aggregation of Drupes
An Aggregation of Drupes is a fleshy fruit, made up of many drupes but formed from a single flower, each drupe containing one seed.
This is a Raspberry (Rubus idaeus). Other fruits of this type are: Loganberry (Rubus), Blackberry (Rubus fruticosus).
/
Pome
A Pome is a fleshy fruit with a thin skin, not formed from the ovary but from another part of the plant. These are sometimes called Accessory Fruits. The seeds are contained in chambers in the centre of the fruit.
This is an Apple (Malus domestica). Other fruits of this type are: Firethorn (Pyracantha), Hawthorn (Crataegus), Medlar (Mespilus germanica), Pear (Pyrus communis), Quince (Cydonia oblonga).
/
Hesperidium
A Hesperidium is a berry with a tough, aromatic rind.
This is an Orange (Citrus sinensis). Other fruits of this type are all Citrus fruits: Citron (Citrus medica), Grapefruit (Citrus x paradisi), Kumquat (Fortunella), Lemon (Citrus limon), Lime (Citrus aurantifolia).
There are other types of fleshy fruit which some people classify separately. A Hep or Hip is a fleshy fruit containing achenes, as in the Rose (Rosa); a Pepo is a fleshy fruit with a leathery skin, formed from an inferior ovary. This type of fruit is found only in members of the Gourd Family (Cucurbitaceae) - Cucumbers (Cucumis melo), Water Melon (Citrullus lanatus), Pumpkin (Cucurbita maxima), and Pseudocarp.
/
Pseudocarp
A Pseudocarp is a false fruit, because it does not contain the seeds. The seeds are achenes, on the outside of a fleshy fruit.
This is a Strawberry (Fragaria x ananassa).
FLESHY FRUITS
formed from a group of flowers
There are a few fruits formed from a group of flowers (inflorescence) rather than just one, but which form only one fruit. These are Sorosis, as in the Mulberry (Morus), Syngonium, as in the Fig (Ficus), and Coenocarpium, as in the Pineapple (Ananas).
DRY DEHISCENT FRUITS
/
Follicle
A Follicle is a dry dehiscent fruit which splits on one side only. It may contain one or many seeds.
This is the fruit of a Columbine (Aquilegia). Other fruits of this type are: Delphinium (Delphinium), Larkspur (Consolida), Love in a Mist (Nigella damascena), Milkweed (Asclepias), Peony (Paeonia).
/ Legume
A Legume is a dry dehiscent pod that splits on two sides.
This is the fruit of a Sweet Pea (Lathyrus odoratus). Other fruits of this type are all in members of the Pea Family (Leguminosae/Fabaceae): Acacia (Acacia), Alfalfa (Medicago sativa), Liquorice (Glycyrrhiza glabra), Flamboyant (Delonix regia), Pea (Pisum sativa), Peanut (Arachis hypogaea), Redbud (Cercis occidentalis), Runner Bean (Phaseolus coccineus), Wisteria (Wisteria).
/
Lomentum
A Lomentum is a dry dehiscent fruit, a legume constricted between the seeds.
This is the fruit of a Golden Chain Tree (Laburnum anagyroides). Other fruits of this type are: Sophora (Sophora), Tick Trefoil (Desmodium).
/
Silique
A Silique is a dry dehiscent fruit. It is long and thin, splits down the two long sides, and has a papery membrane (the septum) between the two halves.
This is the fruit of a Wallflower (Erysimum cheiri). Other fruits of this type are all in members of the Cabbage Family (Brassicaceae): Aubrieta (Aubrieta x cultorum), Cabbage (Brassica olearacea), Honesty (Lunaria annua), Radish (Raphanus sativus).
A silique which is less than twice as long as broad is called a Silicula.
Capsule
A Capsule is the most common fruit type. A Capsule is a dry fruit which splits open to release the seeds.
These plants all have fruit capsules: Cotton (Gossypium), Eucalyptus (Eucalyptus), Horse Chestnut (Aesculus hippocastanum), Jimson Weed (Datura), Mahogany (Afzelia), Witch Hazel (Hamamelis).
There are several types of Capsule, depending on how the fruit splits.
/
Valvate Capsule
A Valvate Capsule is a dry dehiscent fruit in which the tips of the seed capsule split.
This is the fruit of a Campion (Silene). Other fruits of this type are: Jacob's Ladder (Polemonium), Pink (Dianthus), Primrose (Primula).
/ Porose Capsule
A Porose Capsule is a dry dehiscent fruit, opening with pores or holes around the top.
This is the fruit of a Poppy (Papaver). Other fruits of this type are: Blue Poppy (Meconopsis), Prickly Poppy (Argemone).
/ Loculicidal Capsule
A Loculicidal Capsule is a dry dehiscent fruit, splitting along the locule (midrib of each ovary).
This is the fruit of Stinking Gladwyn (Iris foetidissima). Other fruits of this type: Evening Primrose (Oenothera), Valotta (Cyrtanthus elatus), and members of the Violet and Lily Families.
Circumscissile Capsule
A Circumscissile Capsule is a dry dehiscent fruit, opening by splitting through the centre of the fruit, so that the top of the capsule lifts off like a lid. An example of this type of fruit is Pimpernel (Anagallis)
A Septicidal Capsule splits along the septa (joints of the ovary) as in the Foxglove (Digitalis).
DRY INDEHISCENT FRUITS
/ Achene
An Achene is a single-seeded dry indehiscent fruit in which the seedcoat is not part of the fruit coat.
This is the fruit of a Sunflower (Helianthus annuus). Other fruits of this type are: Buttercup (Ranunculus), Clematis (Clematis), Coreopsis (Coreopsis), Dahlia (Dahlia), English Marigold (Calendula), Zinnia (Zinnia).
/
Cypsela
A Cypsela is a single-seeded dry indehiscent fruit that develops from a one part inferior ovary (on the stalk side of the flower). They are sometimes included with Achenes.
This is the fruit of a Dandelion (Taraxacum officinale). Other fruits of this type are found in the same plant family, the Daisy Family (Asteraceae).
/
Nut
A Nut is a large single hardened achene.
This is a Chestnut (Castanea sativa). Other fruits of this type are: Acorn (Quercus), Hazel (Corylus avellana), Hickory (Carya).
/
Nutlet
This is not a classification that seems to be recognised everywhere, but the Mint Family (Lamiaceae) is a very large plant family, and has a particular type of seed which is not quite any of the normal ones, so I thought it should be included somewhere.
The fruits of this family are single-seeded achene-like nutlets, which are held at the bottom of the calyx.
This is the fruit of a Salvia (Salvia). All members of the Mint Family (Lamiaceae) have this type of fruit.
/
Caryopsis
A Caryopsis is a simple dry indehiscent fruit, like an achene, but with the seedcoat fused with the fruit coat.
This is the fruit of Sweetcorn (Zea). Other fruits of this type are all members of the Grass Family (Poaceae): Barley (Hordeum), Oats (Avena), Rice (Oryza), Rye (Secale), Wheat (Triticum).
/
Samara
A Samara is an independent dry indehiscent fruit which has part of the fruit wall extended to form a wing (i.e. not a winged seed inside another type of seed pod).
This is the fruit of a Maple (Acer). This is a Schizocarpic Samara, because the fruit splits into its separate Samaras. Other fruits of this type are: Ash (Fraxinus) - also Schizocarpic, Elm (Ulmus).