Transport Of Solute And Sugar Translocation In Plants Pdf
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Source-to-sink transport of sugar is one of the major determinants of plant growth and relies on the efficient and controlled distribution of sucrose and some other sugars such as raffinose and polyols across plant organs through the phloem. In this paper, we summarize current knowledge about the phloem transport mechanisms and review the effects of several abiotic water and salt stress, mineral deficiency, CO 2 , light, temperature, air, and soil pollutants and biotic mutualistic and pathogenic microbes, viruses, aphids, and parasitic plants factors. Concerning abiotic constraints, alteration of the distribution of sugar among sinks is often reported, with some sinks as roots favored in case of mineral deficiency.
Translocation is the process within plants that functions to deliver nutrients and other molecules over long distances throughout the organism.
Sugar Transport in Plants: Phloem
Source and sink 2. Pathway of translocation 3. Source-sink pathways follow patterns 5. Materials transported 6. The mechanism of phloem transport 7. The Pressure -Flow Model 8. Phloem loading and unloading 9. SlideShare Explore Search You. Submit Search. Home Explore. Successfully reported this slideshow. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads.
You can change your ad preferences anytime. Translocation of food in plants. Upcoming SlideShare. Like this presentation? Why not share! Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Published in: Science. Full Name Comment goes here. Are you sure you want to Yes No. Namgyal Wangmo at Student.
Ansar Alvi. Sahin Mondal. Nandram Suman at pg college damoh. Anand Sagar. Show More. No Downloads. Views Total views. Actions Shares. No notes for slide. Sourceandsink Source: Any exporting organ 1. Storage organ during export phase 2. Apical regions 2. Immature fruits 3. Developing storage organs 5. Source-sink relationships can explain the direction of phloem translocation within the plant. Source - produces more carbohydrates than required for its own needs Sink - produces less carbohydrates than it requires 8.
Young leaf is completely dependent on carbohydrates from other sources. It is a strong sink. As the leaf grows it increasingly provides for its own carbohydrate needs. Mature leaf is largely a carbohydrate exporter source Materials transported The phloem is the vascular system for moving translocating sugars produced in photosynthesis and other substances throughout the plant.
The mechanism of phloem transport The Pressure-Flow Model In source tissue… sugars are moved from photosynthetic cells and actively loaded uses ATP energy into companion cells and sieve tube elements. Solute potential increases 2. Phloem solution moves along a gradient of pressure generated by a solute concentration difference between source and sink ends of the pathway Phloem Loading: Where do the solutes come from?
Generaldiagramoftranslocation Physiological process of loading sucrose into the phloem Physiological process of unloading sucrose from the phloem into the sink Pressure-flow Phloem and xylem are coupled in an osmotic system that transports sucrose and circulates water.
Pressureflowschematic The pressure-flow process Build-up of pressure at the source and release of pressure at the sink causes source-to-sink flow. At the source phloem loading causes high solute concentrations. At the sink y is lower outside the cell due to unloading of sucrose. Osmotic loss of water releases hydrostatic pressure. Xylem vessels recycle water from the sink to the source.
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Plants need an energy source to grow. In seeds and bulbs, food is stored in polymers such as starch that are converted by metabolic processes into sucrose for newly-developing plants. Once green shoots and leaves begin to grow, plants can produce their own food by photosynthesis. The products of photosynthesis are called photosynthates, which are usually in the form of simple sugars such as sucrose. Sources are the structures that produce photosynthates for the growing plant. The sugars produced in the sources, such as leaves, must be delivered to growing parts of the plant.
on translocation to a search for the mechanism of rapid longitudinal move- ment of foods solution through sieve tubes or phloem, related,at leastindirectly, to activ- organization allowing a ready flow of "sugars, nitrogen, phosphorus, po- movement will adequately explain the upward transport of mineral nitro- gen.
Pressure flow hypothesis
The below mentioned article provides an overview on the translocation of solutes in plants. According to the classical concept inorganic solute substances are carried in the xylem vessels with the ascending sap of water in the transpiration stream whereas phloem is the pathway of downward translocation of organic solutes synthesised foods like sugars, amino acids, etc. The classical concept of movement-of inorganic solutes upwards through the xylem is unquestionably true but it is difficult to estimate with certainty the proportion of mineral salts thus translocated. Any solute conducted through the xylem is carried along with the ascending streams of water which are pulled up through the plant by transpirational suction. The rates at which inorganic solutes are translocated through the xylem vessels correspond closely with the rates of translocation of water.
The pressure flow hypothesis , also known as the mass flow hypothesis , is the best-supported theory to explain the movement of sap through the phloem. This creates turgor pressure, also known as hydrostatic pressure , in the phloem. Movement of phloem sap occurs by bulk flow mass flow from sugar sources to sugar sinks. The movement in phloem is bidirectional, whereas, in xylem cells, it is unidirectional upward. Because of this multi-directional flow, coupled with the fact that sap cannot move with ease between adjacent sieve-tubes, it is not unusual for sap in adjacent sieve-tubes to be flowing in opposite directions.
Water potential is the measure of potential energy in water and drives the movement of water through plants. Plants are phenomenal hydraulic engineers. Using only the basic laws of physics and the simple manipulation of potential energy, plants can move water to the top of a meter-tall tree.
SUGAR TRANSPORT IN THE PHLOEM
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