Kingdom Plantae

 

The term plant is used to describe organisms that contain the following characteristics:

$                   ability to synthesize carbohydrates by photosynthesis

$                   presence of cellulose in cell walls

$                   alternation of generations in their life cycles

$                   lack of mobility

 

Plant Diversity

$                   300 000 to 500 000 species of identified plants

$                   no one typical example of a plant

$                   three broad categories of plants:

1.                  Aquatic plants

2.                  Non-vascular plants

3.                  Vascular plants

 

$                   This system of classification of plants is based on the evolutionary relationships and adaptations that have occurred over million of years.

$                   For example, land plants have adapted 3 primary adaptations to survive in their surroundings.  These 3 adaptations are:

1.                  The evolution of structures and systems for the transport of water.

2.                  Roots, stems and leaves

3.                  A method of reproduction that did not depend on water for the dispersal of gametes

$                   the stage of a plant that produces gametes is called a gametophyte (Haploid chromosome number).

$                   the stage that produces a spore is a sporophyte (diploid chromosome number).

$                   the general evolutionary trend in plants is the more complex they are the more time invested in the complex diploid form.

Aquatic Plants

 

$                   the simplest of plants live surrounded by water because water will: provide support; keep cells from drying out; provide nutrients; and allows for the dispersal of sex cells.

$                   most aquatic plants belong to one of three divisions, commonly known as green, brown and red algae. (Insert contents of table 19.2)

$                   most aquatic plants are multicellular, but some are unicellular, filamentous or colonial.

$                   the multi-celled body of an aquatic plant is called a thallus (plural: thalli).  A thallus lacks conductive tissue as well as true roots, stems, and leaves.

 

Plant life on land

 

$                   plants such as mosses, liverworts and ferns represent the beginning of what eventually evolved into larger and more complex seed bearing plants such as conifers and flowering plants.

$                   when comparing plants such as mosses and fir trees, we see that there are some distinct differences.

$                   Mosses are smaller and closer to the ground where as fir trees are much larger.  This difference can be attributed to vascular tissue that is present in the fir trees.

$                   vascular tissue or conducting tissue called xylem and phloem.

$                   xylem is a vascular tissue that carries water and minerals to the leaves.

$                   phloem is a vascular tissue that transports food, synthesized in the leaves to the rest of the plant.

$                   plants containing these structures are called vascular plants.

$                   plants without these structures are called non-vascular plants.

$                   Non-vascular and vascular plants have evolved along separate lines, they share some important characteristics:

$                   both contain a cuticle - a noncellular layer secreted by epidermal cells, designed to protect cells from drying out;

$                   a stomata - pores in the epidermis of plants, particularly in leaves.  Stomata (single: stoma) permit the exchange of gases between the plant and the atmospheric air;

$                   and complex reproductive structures.

 

Non-Vascular ALand@ Plants

$                   non-vascular land plants, or bryophytes, are confined to moist habitats because they need water for sexual reproduction to occur.

$                   they live close to the ground and are abundant in wetlands, rainforests and roadside ditches.

$                   there are three classes of non-vascular plants: mosses, liverworts and hornworts.

$                   bryophytes are generally small plants, less than 20 cm tall.

$                   they have leaf-like, stem-like and root-like structures.

$                   most species have rhizoids, root like filaments that anchor the plant to the substrate.

$                   the thin leaf-like structures are usually one cell layer think and are located on the top of a short main stalk.  This leaf is used to absorb water and minerals and to perform photosynthesis.  Water moves through the plant via cell to cell diffusion.

$                   moss, which can hold large amount of water, is the most common example of a bryophyte

$                   sphagnum also known as peat moss is a common example.

$                   reproduction in mosses shows an interesting relationship between the sporophyte and the gametophyte generations.

$                   in mosses, both generations are contained on the same plant, which is unique to land plants.

$                   when the moss matures the sporangium breaks open and releases the spores.

$                   when moss spores germinate it grows into a filamentous structure called a protonema, which resembles filamentous green algae

$                   the protonema is the gametophyte of moss and forms the >carpet= effect

$                   after several months of development, the gametophyte produces:

1.                   male sex organs, called antheridia (singular: antheridium) which are sperm bearing structures;

2.                  and female sex organs, called archegonia (singular: archegonium) which are egg-bearing structures.

$                   after fertilization, the zygote develops into a short-lived sporophyte plant, and is nourished as a single stalk from the female gametophyte.

 

Read pages 444 - 449 for homework

 

 

Vascular Plants

$                   vascular plants comprise the division Tracheophyta, which include the true terrestrial plants such as ferns, herbs, shrubs, trees and flowering plants.

$                   the plants in this division transport nutrients, water and minerals via a vascular system

$                   the sporophyte is the generation in which the characteristic vascular tissue, organs and systems are found.

$                   the gametophyte is small, dependent on the sporophyte and short-lived.

$                   with the exception of ferns, vascular plants have developed  reproductive structures that are free of total dependence on water.

$                   vascular tissue provides a continuous internal conduction system between the roots, stems and leaves.  It also provides structural support, a feature that is essential for the large size and long life exhibited by many land plants.

$                   the two main kinds of vascular plants are those that produce seeds and those that do not.

 

Seedless Plants

$                   about 300 million years ago, seedless plants were the dominant land plants and formed extensive forests and swamp-lands.

$                   these early forest and swamp-lands now make up of today=s coal mines.

$                   most of these are now extinct and the modern versions are much smaller than their predecessors.

$                   while adapted to life on land, seedless plants are found mainly in humid habitats because their short-lived gametophytes lack vascular tissue.

$                   water is also necessary for reproduction

$                   seedless plants include true ferns and whisk ferns

$                   ferns are the most common of all seedless plants with just over 12 000 living species identified.

$                   all ferns have conducting tissue

$                   the rhizomes of most ferns are underground.

$                   ferns leaves are called fronds.

$                   the unfolding young fronds found in the spring are called fiddleheads

$                   on the lower surface of the fronds are clusters of sporangia called sori (singular: sorus) that produce thousands of dust-like spores.

$                   Mature spores are released into the air

$                   a germinating spore develops into a small haploid gametophyte, called a prothallus

$                   Antheridia and archegonia develop on the prothallus

$                   as in bryophytes, water is needed to enable the sperm to swim to the non-motile egg.

$                   following fertilization, the zygote will form a new sporophyte.

 

 

 

 

 

 

 

Seed Plants

$                   seed plants are the most widely distributed and complex group of plants on Earth today.

$                   there are more than 270 000 species of seed plants

$                   first seed plants appeared about 370 million years ago

$                   seed plants have separate male and female gametophytes as well as roots, stems, and leaves

$                   a seed contains a plant embryo or a partially developed plant

$                   many seed plants are free-living, but there are some examples of saprophytic or parasitic plants

$                   most seed plants are on land, but examples such as the lilies, pitcher plants and a few trees, show that the wetlands are open to plants

$                   the vascular tissue of seed plants allow them to have a larger range in size

$                   there are two main seed types or groups, gymnosperms and angiosperms

$                   these two words are developed from Greek, where sperma means seed, gymnos means naked, and angeion means vessel.

$                   gymnosperms produce unprotected, or naked seeds, seeds in cone-like structures

$                   angiosperms produce seeds that are enclosed and protected inside the fruit which is formed from the flower

$                   seeds enable plants to survive by resisting dessication

 

Gymnosperms

$                   these include pines, spruces, junipers, firs and other cone-bearing plants

$                   they are characterized by thin, needle-like leaves that are specialized for hot-dry summers and cold winters and moderate rainfall

$                   the needles are covered by a hard waxy cuticle that helps the plant retain moisture

$                   conifers have roots that extend over a wide surface area rather than penetrate deep into the soil, this enables the tree to grow in areas where soil is thin

$                   a pine tree is capable of producing millions of pollen grains which are adapted to float in the wind

$                   once the pollen comes in contact with the female cone of the same tree or a different tree, the pollen grains become trapped in a sticky sap secreted by the female cone

$                   as the sap dries, the pollen is drawn towards the ovule

$                   the pollen produces the male sex cells

$                   it is not uncommon for the time between pollenation and fertilization to take longer than a year

$                   after fertilization, the resulting zygote develops into a conifer embryo.

$                   the embryo and the seed coat are contained within the seed

$                   the seed eventually is released from the pine cone

 

see diagram on page 449

 

Angiosperms

$                   there are over 250 000 species of angiosperms, more than all other plant divisions combined

$                   new species are discover almost daily

$                   angiosperms are the most diverse of all the plants

$                   many angiosperms are successful due to insects, a relationship that has developed over millions of years.

$                   In fact, insects and some angiosperms are so interdependent that one can not live without the other.

$                   This is a result of co-evolution, where they have evolved together to the point that they can not survive without each other

$                   flowers are attractive to insects, birds and some mammals

$                   the flower may account for the greater reproductive success of angiosperms when compared to the cones of gymnosperms

 

 

$                   The Flower

$                   come in all shapes and sizes, color, and give off a wide range of fragrances

$                   all flowers share certain common characteristics

 

see page 451, fig. 19.12

 

$                   stamen- male parts of the flower; made up of the filament, anther and pollen

1.                  filament- the thin stalk

2.                  anther- where pollen grains (male gametes) are formed

$                   carpel/pistil- is the female part of the flower

1.                  stigma- is the sticky part on which pollen grains will land and grow.

2.                  style- is the slender stalk by which the pollen grains reach the ovary.

3.                  ovary- contains the ovule which is attached to the ovary wall by a short stalk

$                   in many angiosperms, highly modified leaves, called carpels, join together to form the ovary.  Inside the ovule is the embryo sac that holds the egg cell.  A small hole in the wall of the ovule is called the micropyle, through which sperm nuclei enter.

$                   sepals- the small green leaf-like structures that surround the carpel and stamen

$                   petals- are the colorful parts of the flower that attract pollinating animals.

$                   nectary- is at the base of each petal, and provides a sugary liquid called nectar

$                   flowers that have carpels, stamens, petals, and sepals, such as lilies and tomatoes, are called complete flowers.

$                   if one or more of these structures are lacking then they are called incomplete flowers

$                   in most species, the petals die off after fertilization

$                   the ovule becomes a seed after fertilization and it along with the remaining structures grow and change into fruit.

$                   the seed contains the embryonic plant and the stored food for the embryo

read page 452 and 453 on reproduction of angiosperms.

 

Angiosperm Diversity

$                   flowering plants are grouped into two classes:

1.                  Monocotyledons (monocots) and

2.                  Dicotyledons (dicots)

$                   a cotyledon is a seed leaf that stores food for the young sporophyte and becomes the first leaf to appear as the seed germinates

$                   common monocots include: grasses, water lilies, onions, orchids, wheat, corn, barley, and rye.

$                   dicots include: maples, oaks, cacti, most forest trees and the majority of flowering plants

 

Page 454 questions 8-15