User:Dracophyllum/flower
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Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants. Typically, they are structured in four circular levels around the end of a stalk. These include: modified leaves that support the flower; petals, often designed to attract pollinators; male parts, where pollen is presented; and female parts, where pollen is received and its movement is facilitated to the egg. When flowers are arranged in a group, they are known collectively as an inflorescence.
The development of flowers is a complex and important part in the life cycles of flowering plants. In most plants, flowers are able to produce sex cells of both sexes. In pollination, these two sex cells are brought together to facilitate sexual reproduction. This can occur between different plants, as in cross-pollination, or between flowers on the same plant or even the same flower, as in self-pollination. Pollen, which contains the male sex cells, is transported between male and female parts. This may come from animals, such as birds and insects, or non-living things like wind and water. The colour and structure of flowers assist in this process.
After pollination, the sex cells are fused together in the process of fertilisation. Through cellular and nuclear divisions, the resulting cell grows into a seed, which contains structures to assist in the future plant's survival and growth. At the same time, the female part of the flower forms into a fruit, and the other floral structures die. The function of fruit is to protect the seed and aid in its dispersal away from the mother plant. Seeds can be dispersed by living things, such as birds who eat the fruit and distribute the seeds when they defecate. Non-living things like wind and water can also help to disperse the seeds.
Flowers evolved between 150 and 190 million years ago, in the Jurassic. Plants with flowers replaced non-flowering plants in many ecosystems, as a result of flowers' greater reproductive effectiveness. In the study of plant classification, flowers are a key feature used to differentiate plants. For thousands of years humans have used flowers for a variety of other purposes, including: decoration, medicine, food, and perfumes. In human cultures, flowers are used symbolically and feature in art, literature, religious practices, ritual, and festivals. All aspects of flowers, including size, shape, colour, and smell, show immense diversity across flowering plants. They range in size from 1 mm (1⁄25 in) to 1 m (3.3 ft), and in this way may be either highly reduced and understated, or dominate the structure of the plant.
Development
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Floral development begins with the transformation of vegetative growth into floral growth.[1] This is regulated by both genetic and environmental factors.[2] The eventual formation of a flower starts with a shoot apical meristem (SAM): a group of dividing cells responsible for leaves and buds. The organs which make up a flower—in most cases the sepals, petals, male parts, and female parts—grow out of a growth-limited floral meristem (FM), which a SAM creates.[1] The ABC model of flower development can be used, for many plants, to describe how groups of genes come together to induce each organ being produced.[3] For plants, the transition into flowering is a major change and must occur at the right time so as to ensure reproductive success. Plants determine this time by interpreting both internal and environmental cues, such as day length.[2]
The ABC model was the first unifying principle in the development of flowers, and its major tenets have been found to hold in most flowering plants.[4] It describes how three groups of genes—A, B, and C—are responsible for the development of flowers. These three gene groups' activities interact together to determine the developmental identities of the primordia organ within the floral apical meristem. Alone, A genes produce sepals in the first whorl. Together, A and B produce the petals in the second whorl. C genes alone produce carpels in the centre of the flower. C and B together produce the stamens in the third whorl.[3] This can also be extended to the more complex ABCDE model, which adds an additional two gene groups to explain the development of structures like ovules.[5]
The transition to flowering is one of the major phase changes that a plant makes during its life cycle.[6] The transition must take place at a time that is favourable for fertilisation and the formation of seeds, hence ensuring maximal reproductive success. To meet these needs a plant can interpret important internal and environmental cues such as: changes in levels of plant hormones (such as gibberellins),[7] seasonable temperature, and day length changes.[2] Many perennial (more than two-year lifespan) and biennial (two-year lifespan) plants require cold exposure to flower.[7][8][9] These signals are molecularly interpreted through a complex signal called florigen, which involves a variety of genes. Florigen is produced in the leaves in reproductively favourable conditions and acts in stem tips to force switching from developing leaves to flowers.[10] Once developed, flowers may selectively open and close their flowers at different times of day; usually around dusk and dawn.[11] They may also track the path of the sun to remain warm—potentially both for their own benefit and to attract pollinators. Both of these mechanisms are controlled by a plant's circadian rhythm and in response to environmental changes.[12]
Notes
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References
[edit]- ^ a b Prunet et al. 2009, p. 1764.
- ^ a b c Ausín et al. 2005, pp. 689–705.
- ^ a b Mauseth 2016, pp. 392–395.
- ^ Pandey 2023, p. 19.
- ^ Murai 2013, pp. 379–380.
- ^ Pandey 2023, p. 15.
- ^ a b Pandey 2023, p. 21.
- ^ Xu & Chong 2018, p. 997.
- ^ Li et al. 2022, p. 62.
- ^ Turck, Fornara & Coupland 2008, p. 573.
- ^ Minorsky 2019, pp. 217 & 222.
- ^ Atamian et al. 2016, pp. 587–589.
Bibliography
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[edit]| Sfn number | Validity (y/n) | Fixed if not valid (y/n) | name |
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| 1 | y | rmved extra page | |
| 2 | y | ||
| 3 | y | ||
| 4 | y | ||
| 5 | y | added | |
| 6 | y | ||
| 7 | y | ||
| 8 | y | ||
| 9 | y | ||
| 10 | y | de craene 2010 | |
| 11 | y | de craene 2010 | |
| 12 | y | mauseth | |
| 13 | y | ||
| 14 | y | rapid dev and gamesep | de craene |
| 15 | y | pandey | |
| 16 | y | mauseth | |
| 17 | y | ||
| 18 | y | ||
| 19 | y | ||
| 20 | y | ||
| 21 | y | ||
| 22 | y | ||
| 23 | y | just added padney, it's better | |
| 24 | y | mostly good | |
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| 34 | y | change to p 4. | |
| 35 | y | added petalody ref | |
| 36 | y | ||
| 37 | y | ||
| 38 | y | ||
| 39 | y | rmved earlier refs, added p n. | was leins/sattler |
| 40 | y | see Homeosis, Homology | |
| 41 | y | fixed p range | padney |
| 42 | y | ||
| 43 | y | padney | |
| 44 | y | ||
| 45 | y | fixed p | |
| 46 | y | new ref who dis | |
| 47 | y | new ref who dis again | |
| 48 | y | padney | |
| 49 | y | mausey | |
| 50 | y | swapped for new | Osiadacz 2014 |
| 51 | enough | enough | enough |
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