Download Bio I Lab Instructor: Dr. Rana Tayyar Lab XI Kingdom Plantae Plants

Bio I Lab
Instructor: Dr. Rana Tayyar
Lab XI
Kingdom Plantae
Plants are multicellular eukaryotes that are photosynthetic autotrophs. Plant cells have walls made of cellulose and
store their food in the form of carbohydrates. In most plants, exchange of carbon dioxide and oxygen between the
atmosphere and the photosynthetic interior of leaves occurs via stomata, which are microscopic pores found in the
epidermis of the leaves.
The life cycles of all plants feature an alternation of generations. One generation is the gametophyte, a multicellular
organism with haploid cells; the other generation is the sporophyte, a multicellular organism with diploid cells.
Gametophytes produce haploid gametes by mitosis. Gametes fuse to form the zygote. The zygote develops into
sporophyte. The latter undergoes meiosis to produce haploid spores which in turn undergo mitosis to give rise to the
next generation of gametophytes.
Spores are defined as reproductive cells that develop directly into an organism.
Gametes are reproductive cells that need to fuse to form a zygote which undergoes mitosis to develop into an
organism.
Within the plant kingdom, plant biologists use the term “division” for major plant groups (as compared to phylum,
the highest unit of classification within the animal kingdom).
In the lab, we will be covering the following divisions:
Division Bryophyta: Plants in this division are non-vascular. Example: The mosses.
Division Pterophyta: These are seedless vascular plants. Example: The ferns.
Division Coniferophyta: These are seeded vascular plants that bear naked seeds (i.e. seeds not enclosed in any
specialized chambers). Conifers are gymnosperms (naked seed plants).
Division Anthophyta: These are seeded vascular plants that have seeds enclosed in the ovaries. This division
represents all the flowering plants. It is split into two classes, the monocots (with one embryonic seed leaf or
cotyledon) and the dicots (with two embryonic seed leaves).
Division Bryophyta: The mosses
Haploid gametophyte is the more dominant generation in the bryophytes life cycle. The gametophyte of the moss is
the small plant found in moist areas. There are male and female gametophytes. The former releases sperms from
the antheridium. The latter produces eggs housed in the archegonium. When fertilization occurs, a zygote is formed
and a sporophyte develops on top of the female gametophyte. In a mature sporophyte, the sporangium produces and
releases haploid spores which will develop into protonema (juvenile stage of gametophyte). Protonema develops
into a gametophyte.
Division Pterophyta: The ferns
Diploid sporophyte is the more dominant structure in the life cycle of a fern. The sporophyte consists of the frond,
rhizome and adventitious roots. The frond may consist of several leaflets. It is anchored to the soil by the rhizome
(horizontal stem that grows underground) and adventitious roots (numerous roots that develop from the stem).
Spores are produced in the sporangia clustered to form sori on the underside of the leaflets. When conditions are
favorable, spores germinate to form a heart shaped gametophyte called prothallus. Contrary to mosses, male and
female gametophytes are not separate. When fertilization occurs, a diploid sporophyte quickly develops. The leaves
of most ferns have a distinctive juvenile stage called fiddlehead.
Division Coniferophyta: The conifers
Pines are the largest group of conifers. A pine tree itself is a sporophyte. The gametophyte generation consists of
microscopic stages that grow inside the tree’s cones. A pine tree bears two types of cones. The female cone (the
hard woody one) contains two ovules (megasporangia) at the base of each scale. The male cone (small, soft and
short lived) contains pairs of microsporangia that produce haploid microspores which become the pollen grains
(male gametophytes). When a pollen grain lands on the ovule and enters it, meiosis occurs in the ovule and haploid
spore cells develop into female gametophytes which make eggs. Fertilization does not occur until about a year after
pollination.
Division Anthophyta: Flowering plants
Flower parts: At the bottom of the flower are the sepals, which are usually green. Collectively, the sepals form the
calyx. The calyx encloses the flower before it opens. Above the sepals are the petals which are usually the most
striking part of the flower. The petals form the corolla. The actual reproductive structures are multiple stamens and
a pistil. Each stamen consists of a filament (stalk) and an anther (male organ in which pollen grains develop). The
pistil consists of a style (stalk) with an ovary at the base and a sticky tip known as the stigma. The ovary is a
protective chamber containing one or more ovules, in which the eggs develop.
Two classes of plants are recognized among the flowering plants: The monocots and the dicots:
Main differences between monocots and dicots
Monocots
Dicots
Embryo with single cotyledon
Embryo with two cotyledons
Flower parts in multiples of three
Flower parts in multiples of four or five
Major leaf veins parallel
Stem vascular bundles scattered
Roots are adventitious
Major leaf veins reticulated
Stem vascular bundles in a ring
Roots develop from radicle