What is a Tree?
What do all trees have in common?
--All trees are perennials
--All trees have trunks (some have several, smaller trunks as opposed to one main trunk)
--All trees have crowns or canopies
--There is no general consensus regarding how tall a tree must be but most consider from 10 to 30 feet to be the minimum height
Trees can be separated into two basic categories: gymnosperms and angiosperms
Gymnosperm means 'naked seed'. Gymno = naked
Sperm = seed
Angiosperm means 'vessel seed'. Angio = vessel
Sperm = seed
For the most part, gymnosperm are 'evergreen' and angiosperm are deciduous. However, this is a general rule and there are exceptions.
Examples: The tamarack or larch tree loses its needles in the winter
The American Holly keeps its leaves all year
Both gymnosperms and angiosperms are seed producing plants
Both gymnosperms and angiosperms have vascular tissue that conducts water and nutrients
Gymnosperm means 'naked seed'. Gymno = naked
Sperm = seed
Angiosperm means 'vessel seed'. Angio = vessel
Sperm = seed
For the most part, gymnosperm are 'evergreen' and angiosperm are deciduous. However, this is a general rule and there are exceptions.
Examples: The tamarack or larch tree loses its needles in the winter
The American Holly keeps its leaves all year
Both gymnosperms and angiosperms are seed producing plants
Both gymnosperms and angiosperms have vascular tissue that conducts water and nutrients
Gymnosperm
Gymnosperms do not enclose their ovules in ovaries, they are exposed to the environment. Ovules are the precursor to seeds
Gymnosperms can be separated into four categories:
Gymnosperms can be separated into four categories:
- Cycads: short palm trees found in tropical/subtropical areas
- Gnetophytes: shrubby plants known as Ephedra
- Ginkgo: comprises only one living species; ginko biloba
- Conifers: the largest and most diverse group of living gymnosperms
Conifers
What is a conifer?
Xylem: conducts water and is composed of various cells
in conifers, the main water conducting cells in the xylem are tracheids (tracheids lack perforations in their cell wall)
Phloem: the tissue through which carbohydrate and other compounds are distributed between leaves, stems, and roots
specialized cells in the phloem differ between gymnosperms and angiosperms
- a plant that produces a wood seed cone
- conifer means 'bearer of cones'
- not all conifer produce cones (Example: Juniper trees produce a berry like structure which is a modified cone)
- produce female seed cones along with smaller, male pollen cones
- pollen mainly distributed by the wind (as opposed to animals)
- most are evergreen (larch/tamarack drop their needles)
- conifers are always woody, never herbaceous
- most are trees but there are a few shrubs
Xylem: conducts water and is composed of various cells
in conifers, the main water conducting cells in the xylem are tracheids (tracheids lack perforations in their cell wall)
Phloem: the tissue through which carbohydrate and other compounds are distributed between leaves, stems, and roots
specialized cells in the phloem differ between gymnosperms and angiosperms
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Xylem
-rich in lignin (which support the tree) -composed of dead, hollow cells -one way flow (upward) -transports water and minerals |
Phloem
-transports food (sugars) -composed of live cells with no nucleus -two way flow -also transports amino acids and hormones |
Angiosperm
An angiosperm is a plant with seeds kept within a protective vessel
Angiosperm are flower (and therefor fruit) producing plants
Angiosperm plants evolved from gymnosperms
Every single flowering plant on Earth is an angiosperm
The main difference between an angiosperm and a gymnosperm is that in an angiosperm, the ovule (the precursor to the seed) is protected by a structure known as an ovary.
Once a flower is pollinated, the ovary becomes a fruit (which carries the seeds).
Another difference between conifers and deciduous trees is the type of wood that makes up the trunk. For the most part, deciduous trees and considered 'hardwood' while conifer trees are 'softwood.' As with everything, there are exceptions are some conifers have hardwood and some deciduous trees have softwood. Example: Yew is a conifer that has hardwood and Basswood, and Quaking Aspen are deciduous trees that have softwood.
About 120 million years ago, angiosperms became more numerous than gymnosperms. Why is this so? Conifer trees are able to thrive in areas of poor soil and low resources. These types of locations are often found in higher altitudes. While confers will actually grow better in more fertile soils, their ability to grow in soil with fewer nutrients gives them an advantage. Areas of high fertility tend to be dominated by deciduous trees. Confiner tree grow very slowly, at first. In areas of fertile soil, herbaceous angiosperms will grow so quickly that they crowd out any conifer seedlings that are trying to sprout. Angiosperms are able to grow more quickly than gymnosperms, especially initially due to the difference in leaves and vascular system between the two.
An angiosperm is a plant with seeds kept within a protective vessel
Angiosperm are flower (and therefor fruit) producing plants
Angiosperm plants evolved from gymnosperms
Every single flowering plant on Earth is an angiosperm
The main difference between an angiosperm and a gymnosperm is that in an angiosperm, the ovule (the precursor to the seed) is protected by a structure known as an ovary.
Once a flower is pollinated, the ovary becomes a fruit (which carries the seeds).
Another difference between conifers and deciduous trees is the type of wood that makes up the trunk. For the most part, deciduous trees and considered 'hardwood' while conifer trees are 'softwood.' As with everything, there are exceptions are some conifers have hardwood and some deciduous trees have softwood. Example: Yew is a conifer that has hardwood and Basswood, and Quaking Aspen are deciduous trees that have softwood.
About 120 million years ago, angiosperms became more numerous than gymnosperms. Why is this so? Conifer trees are able to thrive in areas of poor soil and low resources. These types of locations are often found in higher altitudes. While confers will actually grow better in more fertile soils, their ability to grow in soil with fewer nutrients gives them an advantage. Areas of high fertility tend to be dominated by deciduous trees. Confiner tree grow very slowly, at first. In areas of fertile soil, herbaceous angiosperms will grow so quickly that they crowd out any conifer seedlings that are trying to sprout. Angiosperms are able to grow more quickly than gymnosperms, especially initially due to the difference in leaves and vascular system between the two.
- Leaves: the larger, wider leaves of angiosperms can collect more sunlight and, therefore, produce more carbon for rapidly growing seedling. In contrast, a conifer seedling has very little leaf surface (when a conifer is mature, its total leaf surface can equal or even exceed that of mature deciduous trees).
- Vascular system: the vascular system of an angiosperm is more efficient than that of gymnosperms. This gives angiosperms a distinct advantage in fertile soils because their seedlings can utilize the nutrients more effectively and grow more quickly than conifer seedlings. Because of this, conifer began to evolve to grow in less fertile soils because it is difficult for deciduous trees to grow in such locations.
Conifer Sapling
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Deciduous Sapling
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