Classification/Diagnostic Characteristics: The hammer orchid is an angiosperm, or flowering plant. Its major characteristic is the flower, which contains stamen and/or carpels for reproduction, as well as petals. There are three different types of orchid flowers: megasporangiate, microsporangiate, and perfect. Megasporangiate flowers contain only carpels, microsporangiate flowers contain only stamen, and perfect flowers contain both. Hammer orchids also have leaves, a stem, and roots, similar to all the other flowering plants (13). Kingdom: Plantae Domain: Eukarya Phylum: Magnoliophyta Class: Liliopsida Order: Asparalages Family: Orchidaceae Genus: Drakaea
(5)
Relationship to Humans: Orchids were vigorously studied by Charles Darwin during his lifetime as an example of natural selection. Different orchids had very specialized means of pollination that are specific to their environment, providing great evidence for Darwin's theory (13).
Habitat and Niche: Hammer orchids live in nitrogen-poor soil and require mycorrhizae to aid in water and nutrient absorption (13). They are generally found in forest areas with sandy soil and around winter wet areas; however, D. gracilis is sometimes found in mossy ironstone clearings (8).
Hammer orchids prefer low lying damp areas near bodies of water with little to no competition. They frequently repopulate areas that have been damaged by natural disasters. Areas with water of high salinity have a negative effect on the hammer orchid and they do not populate well in these areas (1).
Predator Avoidance: Hammer orchids do not have a system to avoid any predators. Instead of a physical or chemical barrier or tool, hammer orchids will reproduce by spreading seeds around a larger area to create a larger population. This large population decreases the probability of one population ending completely (13). Also, along with the fact that orchids do not have a system to avoid its predators, many organizations have begun to develop recovery plans for the hammer orchid in hopes of providing it a safer environment away from threats such as other animals, tires from vehicles, maintenance work, and land clearing. Also, there has been an action recently started to collect seeds of the hammer orchid to do further studying in hopes of finding potentially better ways for the plants to continue to prosper. (12)
Nutrient Acquisition: Hammer orchids have a symbiotic relationship with mycorrhizae, a fungi that colonizes the roots of the plant, which helps the plant absorb water and nutrients from the soil. In return, the mycorrhizae receive sugars that the orchid synthesizes through photosynthesis. Carbon dioxide enters through stomata under the leaves, which is used in photosynthesis (1).
Reproduction and Life Cycle: A hammer orchid, like other flowering plants, have flowers as their reproductive organs. The stamen act as the male sex organs while the carpels act as the female sex organs. The pollen from one hammer orchid's stamen is carried by the wind or an insect to the carpel of another, where the egg is found. The sperm from the pollen fertilizes the egg, which grows into an embryo located inside a seed.
Hammer orchids flower in late September and early October, but individual plants may not flower every year. The plant is pollinated by the males of a single species of wasp Thynid wasp. The orchid produces pheromones that the male wasp responds to, and the labellum of the plant resembles a flightless female of the same species. When the male tries to fly of with the female lookalike, it bumps against the column of the flower and deposits and/or picks up pollen and carries it to another flower. (1)
Poor wasp thinks he is mating with a female wasp but really he is just pollinating the orchid
(4)
Growth and Development: Hammer orchid seeds are very small and can be carried by the wind for long distances. Hammer orchids are dependent on a mycorrhizal fungus that allows for seed establishment (germination) and plant growth from the plant's dormant state during the summer (11). Once germinated, it takes two to four years for a seedling to develop into a flowering adult. (1) Drakaea species can grow up to 40 cm tall and have flowers up to 4 cm across. (8)
In mature plants, hormones called auxins cause the plant to grow towards light. Auxin causes the plant to grow faster, so more growth on the side of the plant rich in auxin hormones will cause the plant to curve in the opposite direction. Auxins migrate to the side of the plant not exposed to more light, so the plant will curve towards the sun (6).
Integument: Hammer orchids, like most other plants, have a waxy outer layer that prevents it from drying out, being mechanically damaged, and from entry of microorganisms. Its most important function, however, is to preserve water balance, allowing the plant to grow vertically (9).
Movement: Hammer orchids are stationary, being rooted into the ground where they sprout. Plants can experience phototropism, the "turning" of a plant in response to light direction as a result of different parts of the plant exhibiting different reactions to light (10).
Sensing the Environment: Through phototropism, as stated above, hammer orchids respond to the direction of light it absorbs by growing in that direction. That way, the plant maximizes the total amount of light it takes in (10).
Gas Exchange:
Stomata in the leaves take in carbon dioxide and release oxygen which allows the plant to carry out photosynthesis. Also, when roots and stems are not enclosed in suberin, a waxy substance used to prevent entry of unwanted materials and organisms, the roots and stems can do gas exchange using lenticles (3).
Waste Removal: Hammer orchids use photosynthesis to produce their own sugars, and the oxygen that is produced as well as the carbon dioxide made from cellular respiration are released through the stomata under the leaves (13). Nitrogenous wastes of flowering plants are for the most part stored in vacuoles within the cells. They are then used to form other nitrogenous compounds (14).
Environmental Physiology (temperature, water and salt regulation): Water is essential for plants in photosynthesis and must be kept at high levels inside the organism. Roots in the ground absorb surrounding water and send it into the xylem. When water concentrations are high in a particular area of the plant, transpiration releases water into the air out of the stomata and other areas (15).
Internal Circulation: Inside the stem, water flows through the xylem from the roots to the cells in the plant, Through, adhesion, cohesion, and transpiration, water flows up the xylem. In the phloem, nutrients are transported up and down the tube to different cells inside the orchid. When a certain cell in the plant is low in a nutrient, that nutrient will flow through the phloem down a concentration gradient to the hypotonic cell (13).
Chemical Control (i.e. endocrine system):
Hammer orchids release pheromones that attract male Thynid wasps while the female wasps are still underground. This encourages the males to try to mate with the flowers, which results in the spread of pollen (2). As mentioned above, hammer orchids involve the hormone auxin with growth and development. One of the major functions of auxin is to cause phototropism, the growth of the plant towards the light source (6).
Review Questions
1. Explain what mycorrhizae is and why it is important.
Hammer orchid (angiosperm)
Classification/Diagnostic Characteristics: The hammer orchid is an angiosperm, or flowering plant. Its major characteristic is the flower, which contains stamen and/or carpels for reproduction, as well as petals. There are three different types of orchid flowers: megasporangiate, microsporangiate, and perfect. Megasporangiate flowers contain only carpels, microsporangiate flowers contain only stamen, and perfect flowers contain both. Hammer orchids also have leaves, a stem, and roots, similar to all the other flowering plants (13).
Kingdom: Plantae
Domain: Eukarya
Phylum: Magnoliophyta
Class: Liliopsida
Order: Asparalages
Family: Orchidaceae
Genus: Drakaea
(5)
Relationship to Humans: Orchids were vigorously studied by Charles Darwin during his lifetime as an example of natural selection. Different orchids had very specialized means of pollination that are specific to their environment, providing great evidence for Darwin's theory (13).
Habitat and Niche: Hammer orchids live in nitrogen-poor soil and require mycorrhizae to aid in water and nutrient absorption (13). They are generally found in forest areas with sandy soil and around winter wet areas; however, D. gracilis is sometimes found in mossy ironstone clearings (8).
Hammer orchids prefer low lying damp areas near bodies of water with little to no competition. They frequently repopulate areas that have been damaged by natural disasters. Areas with water of high salinity have a negative effect on the hammer orchid and they do not populate well in these areas (1).
Predator Avoidance: Hammer orchids do not have a system to avoid any predators. Instead of a physical or chemical barrier or tool, hammer orchids will reproduce by spreading seeds around a larger area to create a larger population. This large population decreases the probability of one population ending completely (13).
Also, along with the fact that orchids do not have a system to avoid its predators, many organizations have begun to develop recovery plans for the hammer orchid in hopes of providing it a safer environment away from threats such as other animals, tires from vehicles, maintenance work, and land clearing. Also, there has been an action recently started to collect seeds of the hammer orchid to do further studying in hopes of finding potentially better ways for the plants to continue to prosper. (12)
Nutrient Acquisition: Hammer orchids have a symbiotic relationship with mycorrhizae, a fungi that colonizes the roots of the plant, which helps the plant absorb water and nutrients from the soil. In return, the mycorrhizae receive sugars that the orchid synthesizes through photosynthesis. Carbon dioxide enters through stomata under the leaves, which is used in photosynthesis (1).
Reproduction and Life Cycle: A hammer orchid, like other flowering plants, have flowers as their reproductive organs. The stamen act as the male sex organs while the carpels act as the female sex organs. The pollen from one hammer orchid's stamen is carried by the wind or an insect to the carpel of another, where the egg is found. The sperm from the pollen fertilizes the egg, which grows into an embryo located inside a seed.
Hammer orchids flower in late September and early October, but individual plants may not flower every year. The plant is pollinated by the males of a single species of wasp Thynid wasp. The orchid produces pheromones that the male wasp responds to, and the labellum of the plant resembles a flightless female of the same species. When the male tries to fly of with the female lookalike, it bumps against the column of the flower and deposits and/or picks up pollen and carries it to another flower. (1)
(4)
Growth and Development: Hammer orchid seeds are very small and can be carried by the wind for long distances. Hammer orchids are dependent on a mycorrhizal fungus that allows for seed establishment (germination) and plant growth from the plant's dormant state during the summer (11). Once germinated, it takes two to four years for a seedling to develop into a flowering adult. (1) Drakaea species can grow up to 40 cm tall and have flowers up to 4 cm across. (8)
In mature plants, hormones called auxins cause the plant to grow towards light. Auxin causes the plant to grow faster, so more growth on the side of the plant rich in auxin hormones will cause the plant to curve in the opposite direction. Auxins migrate to the side of the plant not exposed to more light, so the plant will curve towards the sun (6).
Integument: Hammer orchids, like most other plants, have a waxy outer layer that prevents it from drying out, being mechanically damaged, and from entry of microorganisms. Its most important function, however, is to preserve water balance, allowing the plant to grow vertically (9).
Movement: Hammer orchids are stationary, being rooted into the ground where they sprout. Plants can experience phototropism, the "turning" of a plant in response to light direction as a result of different parts of the plant exhibiting different reactions to light (10).
Sensing the Environment: Through phototropism, as stated above, hammer orchids respond to the direction of light it absorbs by growing in that direction. That way, the plant maximizes the total amount of light it takes in (10).
Gas Exchange:
Stomata in the leaves take in carbon dioxide and release oxygen which allows the plant to carry out photosynthesis. Also, when roots and stems are not enclosed in suberin, a waxy substance used to prevent entry of unwanted materials and organisms, the roots and stems can do gas exchange using lenticles (3).
Waste Removal: Hammer orchids use photosynthesis to produce their own sugars, and the oxygen that is produced as well as the carbon dioxide made from cellular respiration are released through the stomata under the leaves (13). Nitrogenous wastes of flowering plants are for the most part stored in vacuoles within the cells. They are then used to form other nitrogenous compounds (14).
Environmental Physiology (temperature, water and salt regulation): Water is essential for plants in photosynthesis and must be kept at high levels inside the organism. Roots in the ground absorb surrounding water and send it into the xylem. When water concentrations are high in a particular area of the plant, transpiration releases water into the air out of the stomata and other areas (15).
Internal Circulation: Inside the stem, water flows through the xylem from the roots to the cells in the plant, Through, adhesion, cohesion, and transpiration, water flows up the xylem. In the phloem, nutrients are transported up and down the tube to different cells inside the orchid. When a certain cell in the plant is low in a nutrient, that nutrient will flow through the phloem down a concentration gradient to the hypotonic cell (13).
Chemical Control (i.e. endocrine system):
Hammer orchids release pheromones that attract male Thynid wasps while the female wasps are still underground. This encourages the males to try to mate with the flowers, which results in the spread of pollen (2). As mentioned above, hammer orchids involve the hormone auxin with growth and development. One of the major functions of auxin is to cause phototropism, the growth of the plant towards the light source (6).
Review Questions
1. Explain what mycorrhizae is and why it is important.
Sources:
1. http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=16753
2. http://www.youtube.com/watch?v=Hv4n85-SqxQ
3.http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/GasExchange.html
4. ciphermagazine.com
5. http://www.gbif.org/species/2833951
6. http://www.ndsu.edu/pubweb/chiwonlee/plsc211/student%20papers/articles00/mplace/mplace.htm
7. http://www.merklesorchids.com/CulturePgs/whatsanorchid.htm
8. http://orchids.chookman.id.au/drakaea/drakaea.html
9. http://www.jstor.org/discover/10.2307/27850044?uid=3739696&uid=2&uid=4&uid=3739256&sid=21102994009877
10. http://leavingbio.net/plant%20responses.htm
11. http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=16753#life_cycle
12. http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=16753
13. Hillis, David M. Principles of Life. Sunderland, MA: Sinauer Associates, 2012. Print.
14. http://www.plantcell.org/content/11/4/587.full
15. http://www.biology-online.org/5/2_plant_water_regulation.htm