two specimens each. Stem root and leaf and obsevation the modification
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Modified Stems, Leaves and Roots
Each plant organ originally evolved in the context of specific environmental imperatives related to terrestrial life. Roots anchor the plant and also absorb water and mineral nutrients. Leaves were adapted to optimize photosynthesis. Stems elevate the leaves, serve as a conduit from the roots to the leaves, and also generate new growth. However, each linage of plants have followed their own unique evolutionary path through time, and in many plant groups stems roots and leaves have become secondarily modified by natural selection in unusual and surprising ways.
Modified Shoots
These are examples of shoots (including both the stem and leaves) that have become secondarily modified.
Bulbs: These shoots are an adaptation for interrupted life....for existence in environments with a dormant season due to annual rainfall variations or to life in the temperate climates.
Thorns: The thorns of hawthorne are modified dwarf shoots.
Tendrils: Tendrils of grape are modified flowering shoots. In this link you can see an ontolical mistake where a shoot is one part tendril and one part flower shoot.
Modified Stems
Rhizomes: While typically competition results in vertical stems, there are environments where horizontal stems are adaptive. These are termed rhizomes.
Tubers: Like bulbs these are adaptations for interrupted life. Irish potatoes are tubers. It is clear that they are stems when you realize that the eyes are axillary buds.
Corms: Like tubers and bulbs these are adaptations for intrrupted life. Often mistakenly called, bulbs, a corm is a solid underground stem, vertically oriented where tupically only one bud germinates at the end of dormancy.
Stolons: These are like rhizomes inthat they are oriented horizontally. However, they are adapted to generate new plants that are clones of the original.
Succulent/photosynthetic Stems: In extremely dry environments, often the leaf becomes reduced and non-photosynthetic, and the stem becomes the primary photosynthetic organ of the plant. A barrel shape provides a low surface to volume ratio which reduces water loss.
Cladophylls: If a plant becomes genetically boxed in, like the plants in the preceeding link, and the environment becomes more mesic, the same set of factors that caused the generic leaf to become thin and flat will work to make barrel-shaped, succulent stems, thin and flat too.
Each plant organ originally evolved in the context of specific environmental imperatives related to terrestrial life. Roots anchor the plant and also absorb water and mineral nutrients. Leaves were adapted to optimize photosynthesis. Stems elevate the leaves, serve as a conduit from the roots to the leaves, and also generate new growth. However, each linage of plants have followed their own unique evolutionary path through time, and in many plant groups stems roots and leaves have become secondarily modified by natural selection in unusual and surprising ways.
Modified Shoots
These are examples of shoots (including both the stem and leaves) that have become secondarily modified.
Bulbs: These shoots are an adaptation for interrupted life....for existence in environments with a dormant season due to annual rainfall variations or to life in the temperate climates.
Thorns: The thorns of hawthorne are modified dwarf shoots.
Tendrils: Tendrils of grape are modified flowering shoots. In this link you can see an ontolical mistake where a shoot is one part tendril and one part flower shoot.
Modified Stems
Rhizomes: While typically competition results in vertical stems, there are environments where horizontal stems are adaptive. These are termed rhizomes.
Tubers: Like bulbs these are adaptations for interrupted life. Irish potatoes are tubers. It is clear that they are stems when you realize that the eyes are axillary buds.
Corms: Like tubers and bulbs these are adaptations for intrrupted life. Often mistakenly called, bulbs, a corm is a solid underground stem, vertically oriented where tupically only one bud germinates at the end of dormancy.
Stolons: These are like rhizomes inthat they are oriented horizontally. However, they are adapted to generate new plants that are clones of the original.
Succulent/photosynthetic Stems: In extremely dry environments, often the leaf becomes reduced and non-photosynthetic, and the stem becomes the primary photosynthetic organ of the plant. A barrel shape provides a low surface to volume ratio which reduces water loss.
Cladophylls: If a plant becomes genetically boxed in, like the plants in the preceeding link, and the environment becomes more mesic, the same set of factors that caused the generic leaf to become thin and flat will work to make barrel-shaped, succulent stems, thin and flat too.
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