Introduction of Seed Plants:
Seed plants are seed generating vascular plants. They are also known as Spermatophyte. They have well grown roots, stems and leaves. Seeds having embryo grows from fertilize egg of very small gametophyte that is entirely dependent on sporophytes, plant form we see around us. Efficient seed dispersal of seed plants account for the constant survival and extensive happening. Fertilization of egg is by male gamete that is brought by pollination, followed by development of pollen tube that carries male gamete to egg. Water is not required in process; therefore seed plants are true land plants.
General Characteristics of Seed Plants:
They are terrestrially adapted that is they are land plants. Gametophytes of seed plants turn out to be more decreased and dependent on sporophytes. They make 2 kinds of spores (Megaspores and Microspores) that are they are heterospores. They experience pollution that replaces swimming as mechanism for delivering sperm to egg. They generate seed.
Gymnosperms are usually categorized in 4 divisions. These are:
i) Coniferophyta - the conifers
ii) Cycadeophyta - Cycads
iii) Ginkophyta - ginko
iv) Gnetophyta - gnetae.
Among gymnospems, conifers are most significant. They have the features which are given below:
They are cone bearing plants having vascular tissue. All are woody plants; great majority been trees with just few shrubs. Species can grow naturally in almost every part of world. They are often governing plants in the habitats. They are of high value, mainly for timber and paper production. The wood of conifers is called as softwood. For eg.: Cypresses, Cedars, Redwoods, Pines etc.
External Morphology of Conifers:
All are wood plants, and the majorities are trees. Majority contain monopocal development (i.e. single, straight trunk with side branches) having optical dominance. Size varies from less than meter, to over 100 meters. They are world largest, tallest and oldest living things.
Ecological Adaptation of Conifer:
They have noticeably scented pesin that is secreted to protect tree against insect infestation and fungal infection of woods. They preserve high rates of photosynthesis at comparatively low temperature. Their needles (leaves) include thick warty coatings and sunken stomatas that avoid excessive loss. Sapwood column is large and acts as the short-term reservoir which supplies water to foliage in drought periods.
The angiosperms are also called as flowering plants. They live in every habitat on earth apart from severe environments. They live as epiphytes (that is living on other plants); as floating and rooted aquatics in both fresh water and Marine habitats, and as terrestrial plants which differ extremely in size, longevity and in general form. They can be small herbs, shrubs, parasitic plants, vines or giant trees. They are also sources for other significant resources like medicine and timber.
Angiosperm is usually categorized into 2, which are:
i) Monocotyledons (Monocots)
ii) Dicotyledons (Dicots).
General characteristics of Angiosperms:
They could be photoautotroph, Saprobes or parasitic. They are generally pollinated by insects, birds, and other animals, whereas some are by wind. They have vessels (xylem and phloem). Monocots comprise grasses, lilies, wheat, corn, palms, whereas dicots comprise roses, oaks, peas, maples, and beans. Angiosperms posse certain external features which extraordinarily differentiate them from other seed plants. This characteristic comprises:
1. Flowers: They have altered leaves sepals which are generally green; Petals are brightly colored and insect pollinated; petals are drab and wind pollinated; it has carpels which is female reproductive organ. And also has stamen which is male reproductive organ.
2. Fruits: It guards documents seeds. They include mature ovary. Simple fruit includes single ovary flower (e.g. Pea pod, apple). Aggregate fruit make from separate flowers (like pineapple) alteration for dispersal has: dispersal by wind, attractive food, burns.
Terrestrial Adaptation of Vascular Plant (Seed Plants)
Vascular plants have cuticle and vascular tissues (Xylem and Phloem). They do not require immediate aquatic habitat. Roots do not have cuticle. They are woody materials composed of Cellulose and lignin.
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