Seed vascular plants consist of gymnosperms and angiosperms. Gymnosperms include three basic groups of trees that are rooted in ancient times: Conifers, such as pine trees, redwoods, firs, cedars, and junipers compose the largest group of gymnosperms, while a smaller variety of tropical palm-like trees forms the second group, and the ginko bilboa tree comprises the third group. Angiosperms are a far larger group of plants than gymnosperms, comprising 80 percent of all currently viable green plants. They are nicknamed the "flowering plants." While gymnosperms and angiosperms are not closely related, they do share certain characteristics as seed vascular plants.
All seed vascular plants have developed root systems that anchor them to the soil and extract the nutrients the plants need for survival.
Seed vascular plants share the characteristic of having a vascular system of internal tubes that transport life-sustaining liquids from the roots to all areas of stem and leaves, similar to a circulatory system in animals.
Seed vascular plants, whether an apple tree or a Ponderosa pine, produce microspores, which are male pollen. In a gymnosperm--like the pine tree--the pollen is borne by wind away from the plant with the intent of germinating female seeds. In an angiosperm, male pollen can be produced within the same flower where the female seed is produced.
A seed vascular plant produces female megaspores, or seeds, that the plant retains through maturity. In a gymnosperm--meaning "naked seed"--the ripe female seed separates from the plant and, if germinated by wind-borne pollen, takes root and develops into a new plant. In an angiosperm--meaning "seed vessel"--the seed germinates while still on the plant and develops inside the plant's enclosed ovaries to fruition. Seeds on a gymnosperm are found within cones, which are really just specially modified leaves. Seeds on a angiosperm are hidden within the plant's ovaries.
Seed vascular plants have leaves for the purpose of photosynthesizing the sun's energy into nutrients. While angiosperms have deciduous leaves that fall in autumn and regenerate in spring, the conifers of the gymnosperm seed vascular plants have needle-like, evergreen leaves that they retain year-round.
Growth in seed vascular plants is centered in specific areas, called meristems and cambia, which increase the length and girth of the plants from year to year. In trees, this results in woody growth in roots, trunk and branches.