Mindblown: a blog about philosophy.
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General Features
In all living gymnosperm groups, the visible part of the plant body (i.e., the growing stem and branches) represents the sporophyte, or asexual, generation, rather than the gametophyte, or sexual, generation. Typically, a sporophyte has a stem with roots and leaves and bears the reproductive structures. As vascular plants, gymnosperms contain two conducting tissues, the xylem and phloem. The xylem conducts water and minerals from the roots…
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Introduction To Conifers or Gymnosperm
Gymnosperm, any vascular plant that reproduces by means of an exposed seed, or ovule—unlike angiosperms, or flowering plants, whose seeds are enclosed by mature ovaries, or fruits. The seeds of many gymnosperms (literally, “naked seeds”) are borne in cones and are not visible until maturity. Taxonomists recognize four distinct divisions of extant (nonextinct) gymnospermous plants—Pinophyta, Cycadophyta, Ginkgophyta, and Gnetophyta—with 88 genera and more than 1,000 species distributed…
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Shoot System Modifications
Entire shoot systems are often modified for such special functions as climbing, protection, adaptation to arid habitats, and water or food storage. The modifications generally involve structural and shape changes to the stem and the reduction of the leaves to small scales. Many of the modifications parallel those previously described for leaves. In the passion flower (Passiflora; Passifloraceae) and grape (Vitis vinifera; Vitaceae), axillary buds develop as…
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Leaf Modifications
Whole leaves or parts of leaves are often modified for special functions, such as for climbing and substrate attachment, storage, protection against predation or climatic conditions, or trapping and digesting insect prey. In temperate trees, leaves are simply protective bud scales; in the spring when shoot growth is resumed, they often exhibit a complete growth series from bud scales…
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Leaves
The basic angiosperm leaf is composed of a leaf base, two stipules, a petiole, and a blade (lamina). The leaf base is the slightly expanded area where the leaf attaches to the stem. The paired stipules, when present, are located on each side of the leaf base and may resemble scales, spines, glands, or leaflike structures. The petiole is…
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Stems
The stem is an aerial axis of the plant that bears leaves and flowers and conducts water and minerals from the roots and food from the site of synthesis to areas where it is to be used. The main stem of a plant is continuous with the root system through a transition region called the hypocotyl. In the developing embryo, the hypocotyl is the embryonic axis that bears the seedling leaves…
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Root Systems
The roots anchor a plant, absorb water and minerals, and provide a storage area for food. The two basic types of root systems are a primary root system and an adventitious root system. The most common type, the primary system, consists of a taproot (primary root) that grows vertically downward (positive geotropism). From the taproot are produced smaller lateral roots (secondary roots)…
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Structure
The basic angiosperm body has three parts: roots, stems, and leaves. These primary organs constitute the vegetative (nonreproductive) plant body. Together, the stem and its attached leaves constitute the shoot. Collectively, the roots of an individual plant make up the root system and the shoots the shoot system.
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General Features
The variety of forms found among angiosperms is greater than that of any other plant group. The size range alone is quite remarkable, from the smallest individual flowering plant, probably the watermeal (Wolffia; Araceae) at less than 2 millimetres (0.08 inch), to one of the tallest angiosperms, Australia’s mountain ash tree (Eucalyptus regnans; Myrtaceae) at about 100 metres (330 feet).…
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Detailed Introduction To Flowering Plants (Angiosperm)
Angiosperm, also called flowering plant, any of about 300,000 species of flowering plants, the largest and most diverse group within the kingdom Plantae. Angiosperms represent approximately 80 percent of all the known green plants now living. The angiosperms are vascular seed plants in which the ovule (egg) is fertilized and develops into a seed in an enclosed hollow ovary. The ovary itself is usually enclosed in…
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