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Phloem is the second type of vascular tissue; it transports sugars, proteins, and other solutes throughout the plant. Phloem cells are divided into sieve elements (conducting cells) and cells that support the sieve elements. Together, xylem and phloem tissues form the vascular system of plants.

Roots: support for the plant

Roots are not well preserved in the fossil record. Nevertheless, it seems that roots appeared later in evolution than vascular tissue. The development of an extensive network of roots represented a significant new feature of vascular plants. Thin rhizoids attached bryophytes to the substrate, but these rather flimsy filaments did not provide a strong anchor for the plant; neither did they absorb substantial amounts of water and nutrients. In contrast, roots, with their prominent vascular tissue system, transfer water and minerals from the soil to the rest of the plant. The extensive network of roots that penetrates deep into the soil to reach sources of water also stabilizes trees by acting as a ballast or anchor. The majority of roots establish a symbiotic relationship with fungi, forming mycorrhizae, which benefit the plant by greatly increasing the surface area for absorption of water and soil minerals and nutrients.

Leaves, sporophylls, and strobili

A third innovation marks the seedless vascular plants. Accompanying the prominence of the sporophyte and the development of vascular tissue, the appearance of true leaves improved their photosynthetic efficiency. Leaves capture more sunlight with their increased surface area by employing more chloroplasts to trap light energy and convert it to chemical energy, which is then used to fix atmospheric carbon dioxide into carbohydrates. The carbohydrates are exported to the rest of the plant by the conductive cells of phloem tissue.

The existence of two types of morphology suggests that leaves evolved independently in several groups of plants. The first type of leaf is the microphyll    , or “little leaf,” which can be dated to 350 million years ago in the late Silurian. A microphyll is small and has a simple vascular system. A single unbranched vein    —a bundle of vascular tissue made of xylem and phloem—runs through the center of the leaf. Microphylls may have originated from the flattening of lateral branches, or from sporangia that lost their reproductive capabilities. Microphylls are present in the club mosses and probably preceded the development of megaphylls , or “big leaves”, which are larger leaves with a pattern of branching veins. Megaphylls most likely appeared independently several times during the course of evolution. Their complex networks of veins suggest that several branches may have combined into a flattened organ, with the gaps between the branches being filled with photosynthetic tissue.

In addition to photosynthesis, leaves play another role in the life of the plants. Pine cones, mature fronds of ferns, and flowers are all sporophylls —leaves that were modified structurally to bear sporangia. Strobili are cone-like structures that contain sporangia. They are prominent in conifers and are commonly known as pine cones.

Questions & Answers

state any one specialized animal cell and it's function
Pascal Reply
sperm cell: Fertilization
Tshering
Can DNA and RNA be praticalized
Oyewale Reply
you can make models of them and show how they replicate
Oswald
what is dentition
Tisa Reply
Study of teeths and their functions
Stanisla
what are the function
Tisa
it's not teeths. teeth is plural as well as singular noun. the function of the teeth is to cut and grind food for easier swallowing and for increasing the surface area if the fish as the substrate in which digestive enzymes work
Oswald
dentition is not the study of teeth but the arrangement of teeth in the mouth of species or individuals
Oswald
what are the two types of teeth
Tisa
Function of probosis
Adeola Reply
why do we study biology?
SYDNEY Reply
where biology began
Alhaji
What are chromesome
Talkmore Reply
condensed DNA wrapped with histone
Elias
what is chromosome?
Royd Reply
How can a person who has been in the vascular disease repairs his or her DNA
Rabson Reply
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Shaf Reply
Of wat
John
explanation for wat
Christian
Of war na so dat I can provide
John
Is d process which food is converted into substance dat can be utilize by d body
John
the meaning of disgestion
Charity Reply
because they are considered to be proteins ..lipids,fats, and nucleic acids
Geeta Reply
what is osmosis
Festus Reply
Is the movement of solvent molecules from the region of a higher concentration to the region of lower concentration
Muhammad
It is the movement of solvent from the region of lower concentration to the region of higher concentration through a semi-permeable membrane.
Helen
and diffusion
Prudent
it is the movement of water molecules fro region of higher conc. to the region of lower conc.thro a semi-permeable membrane.
Chansa
Diffusion is the movement of solute molecules from a region of higher concentration to a region of lower concentration.
Quartey
osmosis is the movement of water molecule from the region higher water potential to a region of lower water potential
Pascal
what is the function of Nerve cell?
Pascal
Hello Everyone!! Any good study app recommendations?
HONNEA Reply
For which subject
Sinyinza
Biology:)
HONNEA
Hello everyone!! I want to be sure does exoskeleton consist of endoskeleton? plz help right nw
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Try this one and also biology Olevels
Sinyinza
Thanks!
HONNEA
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Adeetya Reply
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Sinyinza
Thanks for the clarification.
Adeetya
WhAt are the differences between prokaryotic cell and eukaryotic cell
oluwapelumi Reply
Prokaryotic cell is a single celled organism that do not have membrane -bound nuclei.
Quartey
prokaryotes also lack other cell organelles whereas eukaryotes possess an organized nucleus with nuclear envelope and also they have complex locomotory and cytoskeletal structures
Pepper
genetic material is found in cytoplasm in prokaryotic cell while in eukaryotes genetic material is found in nucleus
shams
What cells are the basic unit of life?
Agyeman

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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