examples of c3 and c4 plants
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The gynoecium (from Ancient GreekÎ³Ï…Î½Î®, gyne, meaning woman, and Î¿á¼¶ÎºÎ¿Ï‚, oikos, meaning house) is a term with several meanings in botanical usage. In reference to mosses, liverworts and hornworts, gynoecium refers to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot. More commonly, gynoecium refers to the ovule-producing part of a flower. The gynoecium is typically the innermost whorl of structures in a flower and is surrounded (in perfect flowers) by the androecium (stamens) and (in complete flowers) by the perianth (petals and sepals). The gynoecium is often inaccurately referred to as female because it gives rise to female (egg-producing) gametophytes.
The structural unit that comprises the gynoecium is the carpel. A gynoecium may consist of a single carpel, multiple distinct (unfused) carpels or multiple connate (fused) carpels. Flowers that bear a gynoecium but no androecium are called carpellate. Flowers lacking a gynoecium are called staminate.
Gynoecia give rise to and protect ovules (within one or more ovaries). When mature, gynoecia may function to attract pollinators (through nectaries or visual cues). Gynoecia receive pollen on their surface (usually on a stigma), in some cases actively selecting genetically different pollen so as to promote outcrossing. Gynoecia may facilitate pollen tube growth to the ovule and delivery of the sperm to the egg. The gynoecium forms the pericarp of fruit.
Types of gynoecia
Carpels are the building blocks of the gynoecium. If a gynoecium has a single carpel, it is called monocarpous. If a gynoecium has multiple, distinct (free, unfused) carpels, it is apocarpous. If a gynoecium has multiple carpels fused into a single structure, it is syncarpous. A syncarpous gynoecium can sometimes appear very much like a monocarpous gynoecium. Because of this difficulty in interpreting carpel number and arrangement, some people use the term pistil (from Latinpistillum meaning pestle) to describe the visible structure(s) in a gynoecium. The existence of two different ways of describing gynoecia has led to much confusion, even among botanists. The pistil terminology is less exact and specific, and is more cumbersome, but can be useful in keys and field descriptions where detailed studies are not possible.
* Also called choricarpous
Gynoecium development and arrangement is important in systematic research and identification of angiosperms, but can be the most challenging of the floral parts to interpret.
Each structure in a gynoecium, whether it consists of a lone carpel or multiple fused carpels, usually consists of:
- An enlarged basal portion called the ovary(from Latin ovum meaning egg), which contains 'placentas bearing one or more ovules (integumented megasporangia). A chamber inside an ovary, in which the ovules develop, is called a locule (or sometimes cell). No matter how many carpels fuse together to form a syncarpous ovary, there may be a single locule or more than one locule. If there are multiple locules the walls dividing them are called septa.
- The style (from Latin stilus meaning stake, or stylus), a stalk-like conduit allowing the pollen (male gametophytes) to grow to the egg cell and deliver the sperm.
- The stigma (from Ancient Greek ÏƒÏ„Î¯Î³Î¼Î±, stigma meaning mark, or puncture), usually found at the tip of the style, the portion of the structure that receives the pollen (male gametophytes). It is commonly sticky or feathery to capture pollen.
Carpels begin as small primordia on a floral apical meristem, forming later than, and closer to the (floral) apex than sepal, petal and stamen primordia. Morphological and molecular studies of carpel ontogeny reveal that carpels are most likely homologous to leaves. In some basal angiosperm lineages, for example Degeneria, native to Fiji, carpels begin as a shallow cup and eventually form a folded, leaf-like structure, sealed at its margins by interlocking hairs. No stigma or style exists, but a broad stigmatic crest allows pollen tubes access to two rows of ovules enclosed in the carpel. Carpels, like leaves, generally bear three vascular traces.
In a fully syncarpous gynoecium, the challenge is to determine how many carpels fused to form the gynoecium. Sometimes, the number of stigmas or stigma lobes is useful, as can be ridges on the ovary or locules within the ovary.
The degree of connation (fusion) in a syncarpous gynoecium can vary. Fusion can occur very early in carpel development, or later. In some gynoecia carpels are fused only at their base, but retain separate styles and stigmas. In other gynoecia, the ovaries and styles are fused but the stigmas remain separate. Sometimes (e.g., Apocynaceae) carpels are fused by their styles or stigmas but possess distinct ovaries.
In flowers with multiple distinct carpels, the carpels are nearly always single (apocarpous gynoecium).
Basal angiosperm groups tend to have carpels arranged spirally around a conical or dome-shaped receptacle. In later lineages, carpels tend to be in whorls.
The relationship of the other flower parts to the gynoecium can be an important systematic and taxonomic character. The ovary of the gynoecium can be above the attachment of petals and sepals to the receptacle. In this case the ovary is called superior. This corresponds to the term hypogynous, used to describe a flower with a fully superior ovary.
In some flowers with superior ovaries, (examples include many members of the rose family, Rosaceae) the base of the stamens, petals and sepals are fused into a floral tube or hypanthium. In these flowers, the ovary can be free of or partially adnate (fused) to the hypanthium, but remains at least partially superior. These flower are called perigynous.
In some flowers, the ovary is completely fused to the hypanthium. Only the style and stigma project above the sepals, petals, and stamens, which appear to attach to the top of the ovary. This sort of ovary is called an inferior ovary, and the flower is said to be epigynous. Examples of plant famili
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Answers:CAM plants are susually succulent plants such as pineapples and cacti. C4 plants include crabgrass, corn, and some crops. C3 plants are trees, etc. My guess is that 85% of plants would be C3 plants (in the area I live, anyway). However, I've heard that they are equally dominant in the world becuase both are well suited for the environment and one has not driven the other to extinction.
Answers:PEP combines with carbon dioxide to form oxaloacetate which is 4C oxaloacetate is then converted to malate, which is passed to the bundle sheath cells, where the carbon dioxide is removed and this allows the Calvin Cycle to continue
Answers:What are c3 and c4 plants?
Answers:CAM Plants These are also C4 plants but instead of segregating the C4 and C3 pathways in different parts of the leaf, they separate them in time instead. (CAM stands for crassulacean acid metabolism because it was first studied in members of the plant family Crassulaceae.) At night, CAM plants take in CO2 through their open stomata (they tend to have reduced numbers of them). The CO2 joins with PEP to form the 4-carbon oxaloacetic acid. This is converted to 4-carbon malic acid that accumulates during the night in the central vacuole of the cells. In the morning, the stomata close (thus conserving moisture as well as reducing the inward diffusion of oxygen). The accumulated malic acid leaves the vacuole and is broken down to release CO2. The CO2 is taken up into the Calvin (C3) cycle. These adaptations also enable their owners to thrive in conditions of high daytime temperatures intense sunlight low soil moisture.