FutureStarr

ASeed Seeds

ASeed Seeds

ASeed Seeds

oosphere (“egg”). The pollen tube ultimately penetrates the neck of one of the archegonia. Not until the second growing season, however, does the nucleus of one of the male cells in the tube unite with the oosphere nucleus. Although more than one archegonium may be fertilized, only one gives rise to a viable embryo. During the latter’s development, part of the prothallus is broken down and used. The remainder, referred to as endosperm, surrounds the embryo; it is mobilized later, during germination of the seed, a process that occurs without delay when the seeds are liberated from the female cone during the third year after their initiation. Seeding to grow personal development and skills is healthy for your productivity and well-being for many reasons. The seed metaphor is an important one, especially as we move into changing times.

Seed

In the Late Carboniferous Period (about 315.2 million to 298.9 million years ago), some seed ferns produced large seeds (12 × 6 cm [5 × 2 inches] in Pachytesta incrassata). This primitive ancestral condition of large seeds is reflected in certain gymnosperms (Cycas circinalis, 5.5 × 4 cm [2.2 × 1.6 inches]; Araucaria bidwillii, 4.5 × 3.5 cm [1.8 × 1.4 inches]) and also in some tropical rainforest trees with nondormant water-rich seeds (Mora excelsa, 12 × 7 cm [4.7 × 2.8 inches]). The “double coconut” palm Lodoicea maldivica represents the extreme, with seeds weighing up to 27 kg (about 60 pounds). Herbaceous nontropical flowering plants usually have seeds weighing in the range of about 0.0001 to 0.01 gram. Within a given family (e.g., the pea family, Fabaceae), seed size may vary greatly; in others it is consistently large or small, justifying the recognition of “megaspermous” families (e.g., beech, nutmeg, palm, and soursop families) and “microspermous” ones (e.g., milkweed, daisy, heather, nettle, and willow families).

The smallest known seeds, devoid of food reserves, are found in orchids, mycoheterotrophs (nongreen plants that absorb nutrients from dead organic matter and live symbiotically with mycorrizal fungi—e.g., Indian pipe, Monotropa; coral root, Corallorhiza), carnivorous plants (sundews, pitcher plants), and total parasites (members of the families Rafflesiaceae and Orobanchaceae, or broomrapes, which have seeds weighing as little as 0.001 mg—about 3.5 hundred-millionths of an ounce). Clearly, seed size is related to lifestyle.parasites obtain food from their host, even in their early growth stages, and young orchids are mycoheterotrophs that receive assistance in absorbing nutrients from mycorrhizal fungi that are associated closely with their roots. In both cases only very small seeds that lack endosperm are produced. Dodders (Cuscuta) and mistletoes (Viscum, Phoradendron, Amyema) live independently when very young and accordingly have relatively large seeds. (Source:www.britannica.com)

 

 

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