Angiosperm Traits (Flowering Plants)

Flower

Angiosperm are a group of vascular land plants containing roughly 325,000 species. Like gymnosperms they produce seeds but they also have two structures that make them unique, namely flowers and fruit, in fact this group is often just called "flowering plants". Both of these structures play a key role in reproduction.

Vascular Plant Traits

Prunus serrulata (Japanese Cherry)

Vascular plants differentiate themselves from bryophytes in that they have a developed vascular system of roots, stems and leaves. Besides those important defining traits, they are also different from nonvascular plants because of the dominant sporophyte generation which is not dependent on the gametophyte for food or protection. Basically all other plants not specifically classified as bryophytes are vascular plants. This includes lycophytes (misleadingly called club mosses), ferns, gymnosperms and angiosperms.

Vascular Tissue
xylem: conducts water and minerals up from the plants roots.
phloem: distributes organic nutrients from one part of the plant to another.

Vascular Plant Groups

Seedless Vascular Plant Phyla
- Lycophyta
- Pterophyta

Seed Plant Phyla
Gymnosperms
- Ginkgophyta
- Cycadophyta
- Gnetophyta
- Coniferophyta

Angiosperms
- Anthophya

Bryophytes (Nonvascular Plants)

Liverwort (Pellia epiphylla); image credit: Lairich Rig

Bryophytes are nonvascular plants, which refers to the fact that they lack developed vascular tissue like roots, leaves and stems. This group consists of three phyla of plants: hepatophyta (liverworts), Anthocerophyta (hornworts)  and bryophyta (moss). Plants in this clade are also different from vascular plants in that the gametophyte stage is the dominant life cycle, while the sporophyte is smaller and has a brief lifespan. The gametophyte form is typically leafy and produces gametes. Sperm must typically swim through a film of water to reach and fertilize the eggs. The resulting zygote becomes an embryo which then forms a sporophyte. This form relies on the gametophyte for nourishment in the form of sugars, minerals, amino acids and water, thus it must stay attached.

Moss (Pogonatum urnigerum) ; image credit: pflanzenliebe.de

Bryophytes such as moss typically prefer moist environments but they can be found anywhere from the antarctic to deserts. In dry areas, they will appear brown and dead until the rain returns, at which point they once again fill with chlorophyll and resume normal functions. Mosses are usually the plants most commonly found growing in walls and rocky areas. Bryophytes are usually responsible for breaking down rock into soil which other plants in turn use for growth and support.

Embryophyte Adaptations to Life on Land

For plants, making the leap to land and all the changes it entailed is arguably one of the most important evolutionary feats to date. Not only was this beneficial to them, it paved the way for land animals. Formally known as embryophytes because of the fact that the embryo sporophyte is protected my the parent gametophyte, land plants literally make our lives possible.

There are a few important adaptations that allowed embryophytes to thrive outside the relative comfort of watery environments. This article should give you a good understanding of these important difference between land plants and their algal precursors. It should come as no surprise the the majority of the defining characteristics of embryophytes are those that enable them to survive on land and successfully reproduce.

Alternation of Generations
Land plants have a life cycle which alternates between a multicellular gametophyte and sporophyte stage. Although this is seen in some algae, it is not a process used by charophytes, which are believed to be the group of algae most closely related to land plants.

Multicellular, Dependent Embryo
Zygotes within the gametophyte eventually form the multicellular embryos. These are in turn fed and protected by the parent plant. This in fact is what gives embryophytes their name.

Multicellular Gametangia
The gametes of land plants are produced within multicellular organs called gametangia. Archegonia are the female gametangia, which produce eggs and the sperm are produced by antheridia.

Walled Spores
Plant spores are encased within a tough polymer known as sporopollenin to protect them, allowing dispersal through dry air. These spores are produced by the sporophyte from organs called sporangia.

Apical Meristems
This refers to the undifferentiated cells of plants which become roots, stems, leaves and other structures. The growth of plant apical meristems are continuous as long as the plant lives.

This video (after the jump) provides some more helpful information. Enjoy!

How Plants Respond to Stimuli

One of the attributes of all living things is the fact that they respond to external stimuli. Of course that doesn't mean if you yell at a potato you should expect it to shudder with fear. Plant responses to stimuli typically encompasses the phenomenon known as tropism. This article gives a bit more information on the subject. Also check out the video after the break.