Plants appeared on land about 425 million years ago and the evolutionary history of the plant kingdom reflects increasing adaptation to the terrestrial environment. Plants have organs and organ systems. The leaves collect and absorb sunlight to convert to glucose. The leaves have a waxy coat on them to shield against water. The root system, which branches out, provides support and absorbs water. The stem provides support and the petal / flower / bud is the reproductive organ of the plant.
What distinguishes kingdom plantae from all the other kingdoms, is that the cells of kingdom plantae have cell walls made of cellulose that are used to support the plant. This cell wall is not a semi-permeable membrane and the cell cannot transport material and nutrients in and out of the cell walls. For this function there is the large central vacuole that stores water and chemicals for use inside of the cell. Another characteristic belonging only to kingdom plantae is their chloroplasts, the organelle that converts light energy into chemical energy inside the plant where the energy is stored as sugar. Their ability to convert inorganic matter (atmospheric CO2) to organic matter using photosynthesis keeps us humans in kingdom animalia alive.
multicellular with cell walls made of cellulose
Prokaryotic / eukaryotic:
photosynthesis (absorbs light)
both sexual and asexual
land and water
Hetero / Chemo / Autotrophic:
General Characteristics of Plants:
Multicellular eukaryotes that are photosynthetic autotrophs.
Contain chloroplasts with the photosynthetic pigments chlorophyll a, and b and carotenoids.
Cell walls containing cellulose.
Food reserve is starch that is stored in plastids.
Aerial parts are coated with a waxy cuticle that helps prevent desiccation.
Gas exchange cannot occur across the waxy cuticle so specialized openings on the under surface of the leaf, called stomata, allow gas exchange.
Reproductive adaptations necessary as plants moved from and aquatic to a terrestrial environment
Gametes must be dispersed in a nonaquatic environment. Plants produce gametes within gametangia, organs with protective jackets of nonreproductive cells that prevent the gametes from drying out. The ovum is fertilized within the female organ.
Embryos must be protected against desiccation. The zygote develops into an embryo that is retained for awhile within the female gametangia’s jacket.
All plant life cycles have “Alternation of Generation”.
A haploid gametophyte generation produces and alternates with a diploid sporophyte generation. The sporophyte in turn produces the haploid gametophyte.
The life cycles are heteromorphic; sporophytes and gametophytes differ in morphology.
The sporophyte is larger more conspicuous and more dominate in all except the Bryophytes and their relatives.
To explore the taxa of plant kingdom click Taxonomic Exploration of Kingdom: Plantae