I. SYNONYMS: conifers

II. NUMBER: ~ 560 extant species

III. PHYLUM CHARACTERISTICS

• A. Structure
  • Habit: The conifers have needle-like or scale-like leaves and usually have a strong monopodial (text with tooltip) Monopodial (adj.) pseudopodia describes the condition where an amoeboid makes a single major pseudopodium at a time. habit. Ovules are borne in compound cones (except the Taxopsida and some of the Coniferopsida).
  • Pollen (text with tooltip) The collective mass of grains produced within the anthers of flowering plants or the male cones of a gymnosperm. In all seed plants, pollen is generated by the development of a microspore into a microgametophyte. The germination of the pollen grain leads to the development of a pollen tube, which delivers two sperm or sperm nuclei to the egg in the ovule. In flowering plants, mature microgametophyte has only two cells, a tube cell and a generative cell. : Pollen walls with 1 suture (text with tooltip) A pollen grain with one groove or furrow. and a large saccus (text with tooltip) In the form of a sac. or 2 sacci. The microgametophyte has 0-2 prothallial (text with tooltip) Prothallial cells are remnants of the vegetative microgametophyte in pollen grains. cells, a stalk (text with tooltip) One of the products of division of the initial cells in the pollen of some gymnosperms, said to be the homologue of the antheridial stalk. cell, 2 nonflagellated sperm and a tube cell (text with tooltip) A tube cell develops as part of the microgametophyte within the pollen grain. The tube cell directs the growth and development of the pollen tube, which carries the sperm to the egg in an ovule. .
  • Microstrobilus: Simple or compound; the microsporangia are adaxial.
  • Seeds (text with tooltip) Unit of sexual reproduction in some plants. Formed when an ovule is fertilized and comprised of outer coat that encloses stored food and an embryo. : Ovules (text with tooltip) An ovule is a structure that contains the megagametophyte in seed plants. The megagametophyte remains within the megasporangium (the nucellus), which is surrounded by layers of integuments. After fertilization, the ovule develops into a seed. with 1 integument (text with tooltip) The outer covering of an ovule, which becomes the testa of the seed. of 3 tissue layers; no pollen chamber (text with tooltip) In gymnosperms, a cavity just above the nucellus in the ovule, the site where pollen accumulates and germinates. or nucellar (text with tooltip) Central part of a plant ovule; contains the embryo sac. beak. Archaegonia (text with tooltip) The female reproductive organ containing the egg. (each with 2 tiers of 4 neck canal cells (text with tooltip) The central row of cells in the neck of an archegonium; the ventral canal cell is the most proximal, i.e adjacent to the ovum. These cells dissolve allowing sperm to reach the ovum. ) develop at the micropylar (text with tooltip) An opening in the integuments of an ovule that exposes part of the megasporangial wall (a chamber called a pollen chamber in gymnosperms). Thus, in gymnosperms, pollen enters the micropyle and germinates in the pollen chamber. However, because the micropyle is not exposed in flowering plants, their pollen germinates on the stigma. The pollen tube grows through the style, and enters the ovule through the micropyle. end of the megagametophyte. The embryo has many (2-18) cotyledons.
  • Megastrobilus: Compound with ovules associated with cone scales (text with tooltip) A cone scale is an appendage of the compound ovulate strobili in gymnosperms. It is called a scale rather than a megasporophyll because it is a reduced axis of a simple cone. Thus, a gymnosperm ovulate cone is a cone of simple cone axes, each of which bears 2 seeds. ; each scale is subtended by a bract (text with tooltip) A reduced leaf, especially the small, scale-like leaves associated with a flower or flower cluster. .
  • Stems: Monopodial (text with tooltip) Monopodial (adj.) pseudopodia describes the condition where an amoeboid makes a single major pseudopodium at a time. growth with extensive wood. Often, leafy shoots of 2 types: long shoots and spur shoots (text with tooltip) A slow growing, highly reduced shoot. . Stems with many resin canals.
  • Leaves: Needle-like or scale-like. Usually there is a difference between the long shoot leaves and spur shoot leaves.
  • Roots: Protostelic, usually diarch. They can undergo extensive secondary growth (text with tooltip) Secondary vascular tissue develops from a cambium. .
  • Life History of:
    • Pinus

• B. Ecology: These plants are found world-wide. Dominants in the northern temperate and sub arctic forests. These plants have a fossil history which dates from the Carboniferous and Mesozoic.