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Angiosperm (Latin angi-, “enclosed”; Greek sperma, “seed”), common name for the division or phylum comprising flowering plants.
There are two general types of trees angiosperms and gymnosperms. Angiosperms are flowering plants in which the ovule, or seed, is encased in a protective ovary. With about 235,000 species, the angiosperm division is the largest and most diverse plant group. It is divided into dicots, plants with two cotyledons, that include the familiar broadleaf trees such as maple and oak; and the monocots, plants with one cotyledon that include the palms and lily trees.
Unlike angiosperms, gymnosperms (Greek for “naked seed”) do not bear flowers. Their seeds lie exposed in structures such as cones or fleshy cups called arils. The group includes about 500 tree species—including needle-leaf trees (or conifers).
Gymnosperm and Angiosperm Seeds
The term gymnosperm is derived from two Greek words: gymnos, meaning naked, and sperma, meaning seed. The term refers to plants, such as pine and spruce, in which seeds mature on the surface of cone scales. In contrast, the term angiosperm means a seed contained in a vessel and refers to flowering plants, in which seeds mature within a fruit.
Included in the division are most shrubs and herbs, most familiar trees except pines and other conifers, and specialized plants such as succulents, parasites, and aquatic types. Although about 235,000 species are known, many remain obscure. Flowering plants occupy almost every ecological situation and dominate most natural landscapes. About two-thirds occur in the Tropics, where they are rapidly being exterminated by human activities. Only about 1000 species are of major economic importance, and the bulk of the world’s food supply is derived from only 15. Many hundreds more could be useful if properly investigated and developed
Angiosperms are evolved from gymnosperms. So they are more advanced from gymnosperms.
The position of Ovule:
The ovules are located in an ovary which also takes part in fruit formation.
With respect to sporophyte (in plants that alternate between sexual and asexual phases, a plant in its asexual spore-producing phase) the angiosperms are woody, perennial plants and herbaceous plants.
Angiosperm plants possess not only taproot but also various roots and stem modifications. These are meant for the accumulation of food and capable of vegetative propagation.
Leaves are of different forms and size.
(Latin gymn-, “naked”; Greek sperma, “seed”), is common name for any seed-bearing vascular plant without flowers. Gymnosperms are woody plants, either shrubs, trees, or, rarely, vines. They differ from the other phylum of seed plants, the flowering plants, in that the seeds are not enclosed in carpels but rather are borne upon seed scales arranged in cones.
The gymnosperms are the most ancient seed plants; they appear to have arisen from fern ancestors in the Devonian Period (the geologic period, 410 million to 360 million years ago, during which amphibians first appeared and fish became abundant).
Living gymnosperms are distributed worldwide, with a majority, particularly the conifers, in temperate and subarctic regions. Cycads and gnetophytes are mainly tropical to subtropical. There are about 70 genera with 600 – 1000 species of living gymnosperms, far less than many families of flowering plants.
The position of Ovule:
The ovules of gymnosperms are born directly on the upper side of open sporophyllus, that are often produced in cones.
All gymnosperms are woody perennial plants.
Gymnosperms (chiefly conifers) possess taproot systems only.
Leaves of conifers are small and needle-like.
The giant sequoia grows to heights of 83 m (272 ft), with diameters of up to 9 m (30 ft) and a bark thickness of up to 60 cm (24 in). It is believed to live 2400 to 4000 years, making it one of the longest living species on earth. Currently, the logging of sequoias is prohibited.
COMPARISON B/W ANGIOSPERMS AND GYMNOSPERMS:
|1. Plants having naked ovules
2. These plants possess needles.
3. All gymnosperms are woody
4. Gymnosperms possess two types of branches ie long shoots and dwarf shoots called spur.
5. They lack true vessels
6. Xylem is either mesarch or endarch
7. Resin and gum canals are common in gymnosperms
8. Gymnosperms possess sunken stomata
9. Gymnosperms posses cones
10. All gymnosperms are anemophilous (pollination by wind)
11. In gymnosperms, long interval exists b/w pollination and fertilization. (1 year in Pinus)
12. In gymnosperms, the ovules remain covered by one integument (a thin outer covering of seed).
13. In gymnosperms, endosperm arose from nucellus tissues of the embryo sac.
14. The pollens of Pinus bear wings which help in dissemination.
15. They are generally long-lived
16. Gymnosperms are primitive plants arose from fern ancestors.
17. Their seeds are without fruit.
18. They have one to many (1 – 8) cotyledonary leaves in the embryo.
19. Examples are:
|1. Plants having ovules enclosed in an ovary
2. These plants possess foliage leaves
3. Angiosperms may exist in tree, shrub, and herbs forms.
4. Angiosperm possesses only one type of branches.
5. They possess true vessels
6. Angiosperm lack mesarch xylem
7. Uncommon in angiosperms
8. Angiosperms possess true stomata
9. Angiosperms possess flowers
10. Angiosperms are pollinated by anemophilous, hydrophilous, and entomophilous.
11. In angiosperms, the interval is very short.
12. The no of integuments is two.
13. In angiosperms, endosperms arose from the fusion of male gamete and two polar nuclei.
14. They lack any wings.
15. They are comparatively short-lived
16. These are advanced plants arose from gymnosperms ancestors (Gnetales)
17. Their seeds are enclosed in fruit. (pericarp)
18. There are one or two cotyledonary leaves in their embryo (ie monocots and dicots).
19. Examples are:
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