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Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore , is male and the larger megaspore is female. Heterospory evolved during the Devonian period from isospory independently in several plant groups: the clubmosses , the ferns including the arborescent ...
Spores of two distinct sizes (heterospory or anisospory): larger megaspores and smaller microspores. When the two kinds of spore are produced in different kinds of sporangia, these are called megasporangia and microsporangia. A megaspore often (but not always) develops at the expense of the other three cells resulting from meiosis, which abort.
Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores ...
Plant hormones control all aspects of plant growth and development, including embryogenesis, [1] the regulation of organ size, pathogen defense, [2] [3] stress tolerance [4] [5] and reproductive development. [6] Unlike in animals (in which hormone production is restricted to specialized glands) each plant cell is capable of producing hormones.
Plants that are homosporous produce spores of the same size and type. Heterosporous plants, such as seed plants , spikemosses , quillworts , and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male".
However, not all heteromorphic gametophytes come from heterosporous plants. That is, some plants have distinct egg-producing and sperm-producing gametophytes, but these gametophytes develop from the same kind of spore inside the same sporangium; Sphaerocarpos is an example of such a plant. In seed plants, the microgametophyte is called pollen.
Human growth hormone (HGH) is a hormone that’s essential to our development. Most people produce enough HGH throughout their lifetime. Most people produce enough HGH throughout their lifetime.
Most non-vascular plants, as well as many lycophytes and most ferns, are homosporous (only one kind of spore is produced). Some lycophytes, such as the Selaginellaceae and Isoetaceae, [7]: 7 the extinct Lepidodendrales, [8] and ferns, such as the Marsileaceae and Salviniaceae are heterosporous (two kinds of spores are produced).