Plant cell walls represent the most abundant renewable resource on this planet. They are
rich in mixed complex and simple biopolymers, which has opened the door to the
development of wide applications in different technologic fields.
WATER PLAYS A CRUCIAL ROLE in the life of the plant. For every gram of organic matter made by the plant, approximately 500 g of water is absorbed by the roots, transported through the plant body and lost to the atmosphere. Even slight imbalances in this flow of water can cause water deficits and severe malfunctioning of many cellular processes. Thus, every plant must delicately balance its uptake and loss of water. This balancing is a serious challenge for land plants. To carry on photosynthesis, they need to draw carbon dioxide from the atmosphere, but doing so exposes them to...
THE TERM CELL IS DERIVED from the Latin cella, meaning storeroom or chamber. It was first used in biology in 1665 by the English botanist Robert Hooke to describe the individual units of the honeycomb-like structure he observed in cork under a compound microscope. The “cells” Hooke observed were actually the empty lumens of dead cells surrounded by cell walls, but the term is an apt one because cells are the basic building blocks that define plant structure.
Sugars play important roles as both nutrients and regulatory molecules
throughout plant life. Sugar metabolism and signalling function in an intri-cate network with numerous hormones and reactive oxygen species (ROS)
production, signalling and scavenging systems.
Calcium signal transduction is a central mechanism by which plants sense
and respond to endogenous and environmental stimuli. Cytosolic Ca
ele-vation is achieved via two cellular pathways, Ca
influx through Ca
channels in the plasma membrane and Ca
release from intracellular
) is the most abundant inorganic cation in plant cells.
Unlike animals, plants lack sodium⁄potassium exchangers. Instead, plant
cells have developed unique transport systems for K
The pyruvate dehydrogenase complex (PDC) is subjected to
multiple interacting levels of control in plant cells. The first
level is subcellular compartmentation. Plant cells are unique
inhaving twodistinct, spatially separated forms of the PDC;
mitochondrial (mtPDC) and plastidial (plPDC). The
mtPDCis the site of carbon entry into the tricarboxylic acid
cycle, while the plPDCprovides acetyl-CoAandNADHfor
de novofatty acid biosynthesis.
This book will emphasize the physiological and biochemical functions of plans, but it is important to recognize that these functions depends on structures, ehether the process is gas exchangge in the lesf, water,,,
MINERAL NUTRIENTS ARE ELEMENTS acquired primarily in the form of inorganic ions from the soil. Although mineral nutrients continually cycle through all organisms, they enter the biosphere predominantly through the root systems of plants, so in a sense plants act as the “miners” of Earth’s crust (Epstein 1999). The large surface area of roots and their ability to absorb inorganic ions at low concentrations from the soil solution make mineral absorption by plants a very effective process.
LIFE IN EARTH’S ATMOSPHERE presents a formidable challenge to land plants. On the one hand, the atmosphere is the source of carbon dioxide, which is needed for photosynthesis. Plants therefore need ready access to the atmosphere. On the other hand, the atmosphere is relatively dry and can dehydrate the plant. To meet the contradictory demands of maximizing carbon dioxide uptake while limiting water loss, plants have evolved adaptations to control water loss from leaves, and to replace the water lost to the atmosphere.
PLANT CELLS, UNLIKE ANIMAL CELLS, are surrounded by a relatively thin but mechanically strong cell wall. This wall consists of a complex mixture of polysaccharides and other polymers that are secreted by the cell and are assembled into an organized network linked together by both covalent and noncovalent bonds. Plant cell walls also contain structural proteins, enzymes, phenolic polymers, and other materials that modify the wall’s physical and chemical characteristics.
Cells are tiny building blocks that make up all living things. Cells are so small that you need a microscope to see them.
This is the control centre of the cell. It contains chromosomes with DNA instructions for all the cell’s activities, including instructions to make new cells. This is a jelly like substance, in which many of the cell’s activities, e.g. respiration and protein synthesis occur. This is a thin skin around the cell. It is selectivelt permeable, controlling what goes in and out of the cell....
PLANT CELLS ARE SEPARATED from their environment by a plasma membrane that is only two lipid molecules thick. This thin layer separates a relatively constant internal environment from highly variable external surroundings. In addition to forming a hydrophobic barrier to diffusion, the membrane must facilitate and continuously regulate the inward and outward traffic of selected molecules and ions as the cell takes up nutrients, exports wastes, and regulates its turgor pressure.
THE CYTOKININS WERE DISCOVERED in the search for factors that stimulate plant cells to divide (i.e., undergo cytokinesis). Since their discovery, cytokinins have been shown to have effects on many other physiological and developmental processes, including leaf senescence, nutrient mobilization, apical dominance, the formation and activity of shoot apical meristems, floral development, the breaking of bud dormancy, and seed germination.
Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Calcium-mediated perception and defense responses activated in plant cells by metabolite mixtures secreted by the biocontrol fungus Trichoderma atroviride
Plant anion channels allow the efflux of anions from cells. They are
involved in turgor pressure control, changes in membrane potential,
organic acid excretion, tolerance to salinity and inorganic anion nutrition.
In the mid-1990s plant biotechnology burst onto the scene in world agriculture,
beginning a second ‘green revolution’ and precipitating one of the great public debates
of our time. Approximately a decade later, this book describes the impact of genetically
modified (GM) crops on world agriculture, recent advances in the technology and the
areas of research from which the next generation of GM crops is likely to emerge, as well
as addresses the issues of safety and regulation that have dogged the technology,
particularly in Europe.