Averrhoa carambola

Rapid plant movement is seen in many plants and there are different mechanisms based on the speed of the movement and the situation the plant is in. Some plants may make movements within 2 seconds while some may take 20 seconds to complete a motion. Additionally, for some plants the movement can involve action potentials being activated,[12] or it can involve changes in water pressure and fluctuation of ions moving in and out of cells. In the case of the Averrhoa carambola plant it takes about 20 seconds for the leaves to move from their horizontal position to vertical. This mechanism involves the flux of ions and water. When the leaves receive an external stimulus (hands herbivores) this will translate to an electrical stimulus which then leads to the flow of ions (specifically the potassium and chloride) out of the pulvinus. Within the pulvinus, there are flexor and extensor cells, and this is where the change of potassium and chloride concentration occurs. So as you can see in the diagram [where is the diagram?], when the cell is in its turgid state, the leaves are horizontal, and cells are filled with water. So when the chloride and potassium move out of the cells, the water will flux out which results in the leaves facing vertically. This movement of the leaves drooping takes only a couple of seconds as we saw in the video.^{{which video?]} However, when the leaves or the tree is shaken, this will activate contractile proteins that are in the pulvinus, and they will cause the leaves to droop.[13]

There are a few benefits of the drooping of the leaves: one is that it has been hypothesized that when the leaves droop it makes the plant look malnourished and unappealing, so herbivores are compelled to eat a different plant. Additionally, the movement helps the plant with reducing water loss[14] as well as avoid damages.[15]

The mechanism and reasoning for how this movement reduces water loss for plants is not fully known. However, one known mechanism is the closing of the stomatal pores which are the mouths of the plant in which gas exchange occurs. It takes in carbon dioxide which is important for photosynthesis. This movement of the stomatal pores is done by the guard cells that surround the pores. When there is not enough water in the air, the guard cells well release K+ ions into surrounding cells, and this causes water to move out of the guard cells.[16] After the water is moved out the guard cells shrink in size as well as the stomata pores, and this prevents water from escaping through the pores. This information was obtained through Yahyai's research on the starfruit tree's response to differing soil water depletion levels. Trees were grown in a greenhouse, and there were four levels of soil water depletion. Stomatal response, CO₂ levels, and transpiration were recorded and then analyzed.

Finally, the drooping movement in the star fruit trees helps with reducing leaf damage, protecting it from increased leaf temperature, as well as losing photochemical efficiency (light energy being converted to be used for photosynthesis) from the sun. Excess radiation will act as a stimulus to these leaves, and they will respond with rapid movement. The leaf moving to a position that makes it parallel to the light source is important because the leaves will not be directly facing the sun. This information was found through recording sun to leaf area exposure, canopy diameter, and root growth. Trees had different levels of sun exposure, and how the tree responded was measured and analyzed.[15]

Fruit

Fruits, leaves and trunk

Averrhoa carambola has a number of different forms differing in fruit taste, texture, and shape, some are very acidic and others are sweet. The plant is grown in Malaysia and Taiwan, with smaller concentrations in Thailand, Israel, The United States, Brazil, Philippines, China, Australia, Indonesia and the warmer parts of India and other areas of the world with the same climate. It has become a commercial crop in many of these locations, grown for its edible fruits.[21] The flowers need cross-pollination to produce fruit, thus seed raised plants are variable. Plants may flower and bear fruit in about a year after seed germination. Larger plants may bloom year-round in tropical areas as long as environmental conditions are suitable, plants may have flowers, unripe and ripe fruit at the same time. Under other climate and environmental conditions, plants tend to bloom in spring, and then off and on again during the rest of the year. Many different cultivars are grown, most are selected to optimize fruit flavor and maximum fruit production for specific growing areas, with each country or region having their own specific selections.[21]

Averrhoa carambola shrub