Plants

Introduction to Plants

List the general characteristics of plants:

Uses of plants below:

Compare Nonvascular and Vascular Plants:

Angiospermae are a division (or phylum) of plants that produce flowers as part of their reproductive

process. These plants vary widely in size and shape but all have a set of distinctive features. The

remainder of these worksheets deals with the flowering plants (angiosperms).

Plant Structure and Function

Although there are many classes of flowering plants, the two largest and most common are the

monocotyledoneae (monocots) and the dicotyledoneae (dicots).

Differences in Structure between Monocots and Dicots

ROOTS

What are the functions of roots?

• Anchor plants to ground

• Absorb water and minerals from the soil

• Transport materials upwards to the rest of plant

• Storage of food (e.g. starch) made in stems and leaves

What type of root (fibrous or tap) would be better adapted to a drought-stricken environment? Why?

Tap, find ground water

What type of root (fibrous or tap) would be better adapted to an environment with high soil erosion? Why?

Fibrous, secures soil

Near the end of each root there are several different sections of tissues. These tissues allow the root to

grow longer or wider, take in materials from the surrounding environment and anchor the plant into place.

Looking at a cross section of a root the differences between the monocots and the dicots becomes apparent

with the arrangement of the structures around the center of the root.

Stems

What are the functions of stems?

• Support leaves

• Transport materials between roots and leaves (e.g. water, sugar)

• Storage of food (e.g. sugars)

• May be photosynthetic

Herbaceous stems are green (photosynthetic) and usually die back in the winter.

Woody stems are hardier and usually survive the winter.

Both types of stems are found in monocot and dicot varieties, though there is no secondary growth (stem

diameter increases) for woody monocot stems and thus no “tree rings” to use to determine their age.

Leaves

What are the functions of leaves?

• Main function is photosynthesis (carbon dioxide + water --> glucose + oxygen)

• Green colour due to chlorophyll pigment which absorbs energy and reflects green

Adaptations

Plant Tissues

A tissue is a group of cells that work together to perform a specialized function. These cells can be all

identical or there can be several different cells within the tissue. Plants have several different kinds of

tissues that occur in varying amounts depending on the needs of the plant.

Vascular Tissue

The cells in the vascular tissue are organized into a transport system to move materials around the plant

similar to the arteries and veins in the human circulatory system. Although both sets of cells carry water,

one set also carries dissolved minerals while the other set carries dissolved carbohydrates.

In addition to vascular tissue, plants also have fundamental (ground) tissue, meristematic tissue, and

protective tissue. Outline their differences below.

Water and Food Transport

The xylem and phloem cells of the vascular tissue perform the transport of materials around a plant.

Though it is known that this is a complex process and scientists know which cells are involved, the exact

nature of how the cells move the materials is not fully understood. All we can do is theorize.

Water Transport

The xylem cells are responsible for the movement of water and dissolved minerals around a plant.

Although there is water moving through phloem cells, its purpose is to provide a medium to transport

carbohydrates, not to transport water.

Food Transport

The main function of the phloem cells is to transport the carbohydrates produced in the leaves to the roots

for storage and then distribution through the xylem. The phloem cells are living cells, with cytoplasm and

organelles unlike the mature xylem cells which are hollow and empty. This presents a problem when trying

to determine how the phloem cells accomplish transport though this hasn’t stopped scientists from trying.

Pressure-Flow Theory for the movement of carbohydrates:

Useful Plants

Food

What are the 3 major food crops globally?

Wheat, rice, maize (corn)

What was required to convert wild plants into crops?

At least 20 generations of domestication. Artificial selection of desirable traits.

Why can some crops be grown in more climates than others?

Plants with more genetic diversity are more tolerant. Artificial selection has made plants more specialized to specific environment. Plants have more temperature tolerance, slow metabolism. Some plants naturally prepare for droughts. Some plants are very sensitive to soil conditions. 

Textiles and Fibres

What are three main plants used for clothing?

Cotton, flax, hemp

Why do some plants make better fibres (clothing/rope/paper) than others?

Cellulose content, more cellulose = stronger/better fibres. Fiber lengths, longer fibers = better paper/yarn, more bonding/better interlock. Some fibres are easier to extract than others, making them easier to use.

What are some sustainable ways to use plants for textiles and fibres?

Use plants that grow back fast - hemp, bamboo, flax. Water recycling. Agroforestry - crops and textile plants together. Use by products. Shorten supply chains. 

Medicine

Where are many potentially medicinal plants found?

Satpura, Vindhyachal, Amarkantak, pachmarhi, and Patalkot areas.

What are some plants that can be used for medicine (eaten, brewed, etc)?

Aloe vera, echinacea, peppermint, basil.

What are some modern medicines that are derived from an original source in plants?

Aspirin/Willow bark, Morphine/Opium poppy, Quinine (anti-malaria)/Artemisia annora plant, Digoxin (cardiac glycoside)/foxglove. 

Ecosystems

In a food chain, on what trophic level would you find the plants? Why?

First because they produce their own food so they are not eating anyone else 

What nutrient cycle are plants an important part of? How is photosynthesis important for this?

Carbon cycle:

How are plants involved in the water cycle?

Plants absorb water from soil (roots-also helps build water in soil). Transpiration water travels to leaves, evaporates through stomata into air, releases water vapour. Help cycle water from ground -> atmosphere.

Plant Reproduction

The Flower

All flowering plants have, of course, flowers. There is a wide variety of sizes, shapes and colours of flowers,

but they all share similar structures and characteristics. When a plant flowers, it is moving through one of

the stages of its life cycle in order to reproduce.

The flower is the main reproductive structure of the Angiospermae.

POLLINATION

Plants are non-mobile (which can make finding a date difficult) so angiosperms have developed an amazing variety of methods to transfer the male gametes or pollen from plant to plant (cross-pollination). This allows for the exchange of genetic information and the benefits associated with doing so. However, a plant can also mate with itself (self-pollination) if there are no other plants available.

Process of pollination:

Pollen is released from plant and is adapted for distribution to eggs by wind, water, animals

Flowers produce bright colours, sweet smells, and nectar to attract insects and birds to transfer the pollen

Once the pollen is transferred to another plant, it fertilizes the egg in the ovary;

The ovule becomes a seed and the ovary develops into fruit

Three methods of pollen transfer and specific examples of each:

Water: Algae transports by pollen by water

Wind: Pollen carried has wings, due wind carrying pollen has ~1% success, large volumes must be made

Animals: Little waste, needs petals, colours, nectar

Fertilization

Once a pollen grain lands on the stigma (plant sex) the process of creating a new plant can begin. The

plant must first form seeds, and then distribute its seeds.

Seed Dispersal

Once the seeds have been created, the plant needs to scatter them so that they can find a suitable place to

grow and develop without taking resources away from the parent plant.

Four methods of seed dispersal and examples of each:

Wind: Light fluffy seeds, wings, maple key, dandelions

Water: Floats, coconuts

Animals Externally: sticks to fur, burs

Animals Internally: fruits eaten, seeds pass through digestive system unharmed, in feces, birds can activate

Germination

Most seeds go through a period of dormancy before they start to develop into a plant. Often this is because conditions are not favourable for plant development and the seed is waiting until things improve. This ‘hibernation’ can last a few days, a few weeks or even thousands of years. The two major types of plants (monocots and dicots) germinate in similar ways and use the same structures for slightly different functions.

Seedling Development

Since the monocot and dicot plants have slightly different structures they develop from a seed to a mature

plant in slight different ways.

Describe the process of Germination.

• Seeds require heat and moisture for germination

• Gibberellin hormone released (starch broken into simple sugars to provide energy for growing embryo)

• Water is absorbed into seed and seed coat cracks

• Oxygen diffuses into seed for cell respiration

• Radicle emerges and becomes a root

• Hypocotyl emerges and becomes a stem

• Cotyledons form temporary leaves, true leaves develop & plant matures

Monocot seed: 1 cotyledon, endosperm is energy source, corn

Dicot seed: 2 cotyledon, cotyledon is food source

Asexual Plant Reproduction

Vegetative Propagation

• A natural process 

• No seeds or spores are required

• Only one plant is involved so the new plant is genetically identical to the parent

• The new plant grow from parts of the parent plant

• E.g. stems: runners are stems that grow horizontally above ground. They have nodes where buds are formed. These buds grow into a new plant. 

Modified Structures

• Modified stems such as rhizomes, corms, and “eyes” on tubers

• E.g. rhizomes, corms, eyes on tubers

Cuttings

• Fragments of stems, leaves, roots can grow into a new plant

• A cut stem placed in water may begin to from roots and leaves

Grafting

• Attaching a cut-off young branch from one plant onto the stem of another plant

• Allows many copies of the desirable plant to be made

• Cutting does not need to grow roots

Why is asexual plant reproduction used?

• Has been used by early humans to clone crops with desirable traits

What are some disadvantages?

• Reduced genetic diversity: more susceptible to changes in environment

What are some benefits?

• Offspring have same desired traits

• Less time and energy spent on reproduction

• Don’t need a mate

Soil & Soil Nutrients

Like all living organisms, plants require certain nutrients in order to survive and prosper. A plant obtains

most of its nutrients from the surrounding soil through its root system via the movement of water.

Fertilizers

The label on a bag of lawn fertilizer reads 24-6-12. What do these three numbers refer to? What is each

nutrient’s function?

Each number is the percentage of Nitrogen (green growth), Phosphorus (root, flower growth), Potassium (strong, healthy, harty)

Adaptations

Hormones and the Control of Plant Growth

Plants need to be able to coordinate their growth so that they can shape themselves into a useful, efficient

structure to maximize their ability to survive. Like other organisms, plants use complex chemicals known as hormones to help them grow and respond to changing conditions.

Auxins

Produced in the apical meristems, auxins are hormones that respond to the presence of light on the plant.

This will affect the direction and size of plant growth depending on where the sun is located. Changing

levels of auxins also allow the plant to drop its leaves in autumn, stimulate flower production and help

determine apical dominance (the tendency of the plant to grow tall and straight.

Other Hormones

There are other hormones and chemicals that act as hormones within a plant. Some of them stimulate plant growth and others will inhibit growth. These hormones can also be used in agriculture and industry to affect the growth of crop plants and to control the ripening of fruit that is stored or shipped for sale around the world.

Tropisms

Plants also change their growth pattern in response to external stimuli as changes in the environment

around a plant affect its growth. These responses are called tropisms and are controlled by hormones.

COMPARISON OF PRIMARY AND SECONDARY SUCCESSION

Define ecological succession.

Gradual change overtime in the species that form a community

What is a pioneer species? Provide an example.

First species to colonize an area during succession. E.g. lichens, mosses, herbaceous plants

 How are primary and secondary succession different?

Explain how succession and biodiversity are related.

Beginning of succession = low biodiversity. Succession drives biodiversity -> creates niches. 

Give an example of how human activity can cause primary succession and secondary succession. Which type of succession is more often affected by human actions?

• Traditional Suburban yards (grass monoculture)

  • Some allow native plants to colonize

• Forestry companies switch from clear cutting to selectively cutting trees of a specific size (later in succession, more stable)

• Advancing succession

  • Increase biodiversity, in communities eventually

  • E.g. planting species that would eventually arise naturally by succession

• Secondary more affected by humans

Suppose there is a weedy section of grass in the schoolyard (out front by the road). Using what you know about succession, how could you improve the biodiversity of the area?

• Introduce native plant species (grasses, wildflowers, shrubs, etc)

• Remove non-native/invasive species

  • Use many cover crops to prevent regrowth

• Improve soil health

• Avoid frequent mowing

Create a diagram to represent primary succession and secondary succession