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Plant Biology

Plants, characteristics:

  • Eukaryotic organisms

  • Pluricellular (with the cellulose cell wall and starch reserve).

  • Photosynthesizing autotrophs (with chlorophyll a and b).

  • The embryo is protected by a layer of cells -in the early stage of development.

Bryophytes: mosses, liverworts and anthocerans.

Characteristics

  • The first group to conquer the terrestrial environment.

  • They are common in humid and shaded places.

  • The plant is the gametophyte, with gametangia (antheridia and archegonia).

  • Gametes depend on water for transport.

Pteridophytes: ferns and avocets.

Characteristics

  • They are the first tracheophytes.

  • The plant is the sporophyte, with sporangia grouped in sori.

  • Underground stem type in most species (rhizome).

  • Spores are carried by the wind and originate from the prothallium (gametophyte), Gametes depend on water to be transported.

Gymnosperms: pine trees.

Characteristics

  • They are the first spermatophytes -with leaves specialized in producing spores (sporophylls, gathered in strobiles).

  • The plant is the sporophyte, and the strobiles produce microspores (forms the pollen grain) or megaspores (forms the embryo sac).

  • There is no longer dependence on water for fertilization (presence of the pollen tube).

  • After fertilization, the ovule becomes a seed (embryo + nutritive tissue + tegument).

Angiosperms: orange, apple, etc.

Characteristics

  • It is the group with the largest percentage of known plant species.

  • The plant is the sporophyte, and the gametophyte is reduced.

  • In the stamens, there is the pollen sac, where the spores are formed by meiosis, generating pollen grains. In the pistils, meiosis forms the megaspore -this will give rise to the embryo sac.

  • Pollination: transport of the pollen grain from one plant to the pistil of another.

  • Double fertilization occurs (forming the embryo and the endosperm).

  • The endosperm (3n) is the nutritional reserve of the embryo.

  • After fertilization, the ovary becomes a fruit, and the ovules become seeds.

Plant Physiology

Transport of raw sap

  • Salts and water are absorbed by the roots and transported into the plant by the xylem.

  • Root pressure pushes the sap upward.

  • The main factor for the ascent of sap is leaf transpiration and the cohesion between water molecules (cohesion-tension theory).

Leaf Transpiration

  • Transpiration occurs in any part of the plant that is above ground. However, most transpiration occurs in the leaves.

  • The biggest loss of water occurs through the stomas.

  • The stomas open when there is light and water availability.

  • And they close with excessive loss of water or the lack of light.

  • The low concentration of carbon dioxide also stimulates the stomas to open.

Transport of organic sap

  • Organic matter produced in the leaves must be transported to the consuming sources -via the phloem.

  • Sap moves from where hydrostatic pressure is highest (producing organ) to where it is lowest (mass flow theory).

Ring of Malpighi:

  • The removal of a ring -in the bark of the tree- interrupts the flow of the phloem and causes the death of the cells due to lack of nutrients.

  • The phloem, like the xylem, is an important plant conducting tissue. This tissue is concerned with the transport of important substances. Some examples are sucrose, amino acids, hormones, and vitamins.

Plant Biology

Plants, characteristics:

  • Eukaryotic organisms

  • Pluricellular (with the cellulose cell wall and starch reserve).

  • Photosynthesizing autotrophs (with chlorophyll a and b).

  • The embryo is protected by a layer of cells -in the early stage of development.

Bryophytes: mosses, liverworts and anthocerans.

Characteristics

  • The first group to conquer the terrestrial environment.

  • They are common in humid and shaded places.

  • The plant is the gametophyte, with gametangia (antheridia and archegonia).

  • Gametes depend on water for transport.

Pteridophytes: ferns and avocets.

Characteristics

  • They are the first tracheophytes.

  • The plant is the sporophyte, with sporangia grouped in sori.

  • Underground stem type in most species (rhizome).

  • Spores are carried by the wind and originate from the prothallium (gametophyte), Gametes depend on water to be transported.

Gymnosperms: pine trees.

Characteristics

  • They are the first spermatophytes -with leaves specialized in producing spores (sporophylls, gathered in strobiles).

  • The plant is the sporophyte, and the strobiles produce microspores (forms the pollen grain) or megaspores (forms the embryo sac).

  • There is no longer dependence on water for fertilization (presence of the pollen tube).

  • After fertilization, the ovule becomes a seed (embryo + nutritive tissue + tegument).

Angiosperms: orange, apple, etc.

Characteristics

  • It is the group with the largest percentage of known plant species.

  • The plant is the sporophyte, and the gametophyte is reduced.

  • In the stamens, there is the pollen sac, where the spores are formed by meiosis, generating pollen grains. In the pistils, meiosis forms the megaspore -this will give rise to the embryo sac.

  • Pollination: transport of the pollen grain from one plant to the pistil of another.

  • Double fertilization occurs (forming the embryo and the endosperm).

  • The endosperm (3n) is the nutritional reserve of the embryo.

  • After fertilization, the ovary becomes a fruit, and the ovules become seeds.

Plant Physiology

Transport of raw sap

  • Salts and water are absorbed by the roots and transported into the plant by the xylem.

  • Root pressure pushes the sap upward.

  • The main factor for the ascent of sap is leaf transpiration and the cohesion between water molecules (cohesion-tension theory).

Leaf Transpiration

  • Transpiration occurs in any part of the plant that is above ground. However, most transpiration occurs in the leaves.

  • The biggest loss of water occurs through the stomas.

  • The stomas open when there is light and water availability.

  • And they close with excessive loss of water or the lack of light.

  • The low concentration of carbon dioxide also stimulates the stomas to open.

Transport of organic sap

  • Organic matter produced in the leaves must be transported to the consuming sources -via the phloem.

  • Sap moves from where hydrostatic pressure is highest (producing organ) to where it is lowest (mass flow theory).

Ring of Malpighi:

  • The removal of a ring -in the bark of the tree- interrupts the flow of the phloem and causes the death of the cells due to lack of nutrients.

  • The phloem, like the xylem, is an important plant conducting tissue. This tissue is concerned with the transport of important substances. Some examples are sucrose, amino acids, hormones, and vitamins.