Which affects plant growth more??? Gravitropism or phototropism?
Phototropism is much stronger than gravitropism in stems than root. The stem of the plant will actually grow toward whichever direction that has light. So it is very possible that it will grow sideways. I've seen it before in similar experiments. Gravitropism is the dominant response in the roots while phototropism is more dominant in the shoot. If the plant lays on its side, it will grow upward if the light is located on top. It's not actually gravitropism but positive phototropism. And since the stems are growing away from the gravitational pull by growing up, it is also experiencing negative gravitropism. Without a light source, the stems might possibly experience positive gravitropism and grow downward. As a seedling, the roots grow out first. Once it reaches a certain length were the root cap is formed, it will experience gravitropistic response. This mechanism allows the roots to grow downward to get water and in respect, orient the whole plant so that the photosynthetic shoot will grow upward. Once the shoot grows upward, it will experience phototropism. Past experiments show that auxin--a plant hormone--is responsible for phototropism. Basically auxin accumulates on the side of the plant stem that is not exposed to the sun. It causes the cells to elongate by loosening the cell walls. If one side of the stem elongates and the other side exposed to light doesn't, the plant will then bend toward sunlight.
What is the relationship between plant hormones and tropisms ?
Tropisms are controlled by hormone distribution For example - phototropism Plant stems grow towards the light The rate at which a stem elongates is controlled by plant hormones called auxins. The greater the level of auxin, the greater the rate of growth (OK I'm simplifying here, but bear with me, it will be worth it) If the light is shining from one side of the stem, the shaded side accumulates more auxin, so it grows faster that the illuminated side. This causes the stem to grow in the direction of the light. John H
How does gravity affect plant growth?
When plants grow their stem and their leaves grow upward while their roots grow downward. The Direction that a plant grows has nothing to do with the way that you plant the seed .The stem always find their way down. The Stem knows how to find their way to the roots.They always find their way down. If we want to live in the space station or an other planet we would need to Plant Vegtables or Fruit where it would be no gravity . we would face many problems like growing plants because of their diffrent or zero...
Could gravity affect genes turning on/off?
Gravity is the physiological condition under which our bodies evolved and operate. Thus, the expression of genes under gravity conditions is the normal gene expression. Lack of gravity turns on and off quite a few genes, and these changes in gene expression are behind conditions that may develop in microgravity or zero gravity, such as bone loss and muscle atrophy.If you go to PubMed and search for "space flight" and "genes", you'll find numerous publications describing these changes in gene expression. Because of the importance this subject has in space travel, cell lines and model organisms such as rodents and C. elegans have been taken in spaceflights or have been subjected experimentally to microgravity. For example, genes participating in the DNA damage response, for example, increase their expression in response to zero gravity, above the usual increase due to space radiation (http://www.ncbi.nlm.nih.gov/m/pu...)Zebrafish (Danio rerio) are being used extensively in the lab under simulated microgravity to try to understand why and how microgravity affects the way genes are expressed. Check out this page: http://zebrafish.umdnj.edu/resea...
Why does auxin INHIBIT root growth but PROMOTE shoot growth?
Auxins (Indole-3-acetic acid and several similar aromatic rings bonded to acetic acid) don’t accumulate on the shaded side of a plant—sunlight on the opposite side of the plant serves to break down auxins. Since the relative concentration on the shaded side is higher, those cells tend to elongate more—the hormone promotes ELONGATION, which is part of GROWTH. Auxins are produced at the meristems of the plant—the actively dividing branch tips.In the roots, it’s a little more complicated. there are structures in the root, near the tips, called statoliths. They are starch-containing organelles within the root cells. These sink to the bottom of root cells, because they are heavier (composed of starch). This initiates a change in the way the cells channel the auxins, and promotes growth in a downward (mostly) direction. The process is called gravitropism, or geotropism. Roots demonstrate positive gravitropism; stems demonstrate negative gravitropism.
What are examples of tropism in plants?
There are several different examples of tropisms in plants. Gravitropism, or the response to gravity, causes roots to move towards gravity, or down into the soil, to reach water and minerals. It also causes stems to move away from gravity, so that leaves and stems will be in a position to intercept light.Phototropism is the response in plants to unidirectional light coming from one source, such as a lamp or beam of sunlight. Cells on the shaded side of the stem elongate more than the cells on the lit side, causing the stem to turn toward the light.Thigmotropism is plant response to touch. The most common example is the curling response of vines when in contact with an object. The response is controlled by specialized epidermal cells, which mediate the differential growth on each side of the stem. Elongation of cells on one side of the stem cause bending of the stem in the opposite direction.Heliotropism is the response of an entire plant organ, such as a flower or leaf, to the sun's position in the sky. Plants orient leaves at different angles in relation to the sun to regulate temperature, evapotranspiration, and rate of photosynthesis in leaves.
Does the Sun's gravity pull objects on the Earth toward it?
The only way of feeling the gravity of the sun would be to perceive the gradient of the sun's gravitational force. [1] Otherwise, the combination of the earth's and sun's gravities does not allow to distinguish the sun's component.The sun's tidal force hardly can be registered by plants because of their small size compared to the distance to the sun. Actually, not the whole plant is perceiving gravitation, but only specialized cells [2], making perceiving this gradient quite impossible. Our moon has a better chance to make any influence on plants by tidal force and somehow confuse them, but it wouldn't work anyway because of the small size of these statocytes.Generally, I don't think it would be beneficial for plants changing their direction of growth every day from East to West. They are orienting their parts towards the sunlight that makes photosynthesis more effective.Plants don't care about the nature of the force and can grow towards the center of a rotary garden [3] confusing centrifugal forces with gravitation.__________________________1. Tidal force2. Gravitropism3. 8. Rotary hydroponic garden - Hydroponic Nutrient for Indian Hobby grower