Related Experiment Video
Updated: Jul 26, 2026
09:38
Collection and Analysis of Arabidopsis Phloem Exudates Using the EDTA-facilitated Method
Published on: October 23, 2013
Phloem Pressure Differences and C-Assimilate Translocation in Ecballium elaterium
S N Sheikholeslam1, H B Currier
1Department of Botany, University of California, Davis, California 95616.
Plant Physiology
|March 1, 1977
Summary
Phloem turgor pressure directly influences the direction of carbon-14 (¹⁴C)-assimilate translocation in plants. Changes in phloem pressure, manipulated by shoot treatments, correlated with assimilate movement direction.
Area of Science:
- Plant Physiology
- Biochemistry
- Plant Biology
Background:
- Phloem turgor pressure is a critical factor in nutrient transport within plants.
- Understanding assimilate translocation mechanisms is vital for plant science and agriculture.
Purpose of the Study:
- To investigate the role of phloem turgor pressure in directing carbon-14 (¹⁴C)-assimilate translocation.
- To establish the relationship between pressure gradients and assimilate movement in Ecballium elaterium.
Main Methods:
- Manipulating assimilate translocation direction using shoot darkening or defoliation.
- Measuring sieve tube turgor pressure with the phloem needle technique.
- Analyzing ¹⁴C-assimilate distribution via autoradiography and counting.
Main Results:
- A direct correlation was observed between assimilate transport direction and pressure differences in the phloem.
- Darkening of shoot segments led to decreased phloem turgor pressure.
- This pressure decrease enhanced the pressure gradient between source leaves and treated regions, influencing translocation.
Conclusions:
- Phloem turgor pressure gradients are a primary driver of assimilate translocation direction.
- Experimental manipulation of turgor pressure confirms its role in controlling nutrient flow in plants.
Related Concept Videos
00:53Tonicity in Plants
Tonicity describes the capacity of a cell to lose or gain water. It depends on the quantity of solute that does not penetrate the membrane. Tonicity delimits the magnitude and direction of osmosis and results in three possible scenarios that alter the volume of a cell: hypertonicity, hypotonicity, and isotonicity. Due to differences in structure and physiology, tonicity of plant cells is different from that of animal cells in some scenarios.Plants and Hypotonic EnvironmentsUnlike animal cells,...
02:34Water and Mineral Acquisition
Specialized tissues in plant roots have evolved to capture water, minerals, and some ions from the soil. Roots exhibit a variety of branching patterns that facilitate this process. The outermost root cells have specialized structures called root hairs that increase the root surface, thus increasing soil contact. Water can passively cross into roots, as the concentration of water in the soil is higher than that of the root tissue. Minerals, in contrast, are actively transported into root cells.
02:12Short-distance Transport of Resources
Short-distance transport refers to transport that occurs over a distance of just 2-3 cells, crossing the plasma membrane in the process. Small uncharged molecules, such as oxygen, carbon dioxide, and water, can diffuse across the plasma membrane on their own. In contrast, ions and larger molecules require the assistance of transport proteins due to their charge or size. Transport across membranes also occurs within individual cells, playing a variety of essential roles for the plant as a whole.
02:03Xylem and Transpiration-driven Transport of Resources
The xylem of vascular plants distributes water and dissolved minerals that are taken up by the roots to the rest of the plant. The cells that transport xylem sap are dead upon maturity, and the movement of xylem sap is a passive process.
02:02Phloem and Sugar Transport
Like many living organisms, plants have tissues that specialize in specific plant functions. For example, shoots are well adapted to rapid growth, while roots are structured to acquire resources efficiently. However, sugar production is primarily restricted to the photosynthetic cells that reside in the leaves of angiosperm plants. Sugar and other resources are transported from photosynthetic tissues to other specialized tissues by a process called translocation.
01:46The Apoplast and Symplast
Plant growth depends on its ability to take up water and dissolved minerals from the soil. The root system of every plant is equipped with the necessary tissues to facilitate the entry of water and solutes. The plant tissues involved in the transport of water and minerals have two major compartments - the apoplast and the symplast. The apoplast includes everything outside the plasma membrane of living cells and consists of cell walls, extracellular spaces, xylem, phloem, and tracheids. The...