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Competitive inhibition is usually based on the fact that the structure of the inhibitor resembles that of the substrate; hence the strong affinity of the inhibitor for the active site. Competitive inhibition may also occur in allosteric enzymes, where the inhibitor binds to a distant site on the enzyme, causing a conformational change that alters the active site and prevents normal substrate binding.

Such a binding site is called an allosteric site. In this fisiologia vegetal taiz, the competition between substrate and inhibitor is indirect.

Taiz (5a Edición): Libro de Fisiología Vegetal - Ejercicios de Fisiología de las Plantas - Docsity

Competitive inhibition results in an apparent increase in Kmand has no effect on Vmax see Figure 2. By measuring the apparent Kmas a function of inhibitor concentration, one can calculate Ki, the inhibitor constant, which reflects the affinity of the enzyme for the inhibitor. In noncompetitive inhibition, the inhibitor does not compete with the fisiologia vegetal taiz for binding to the active site.


Noncompetitive inhibition is frequently observed in the regulation of metabolic enzymes. The diagnostic property of this fisiologia vegetal taiz of inhibition is that Kmis unaffected, whereas Vmaxdecreases in the presence of increasing amounts of inhibitor see Figure 2.

Fisiología vegetal (Book, ) []

Mixed inhibition is characterized by effects on both Vmax which decreases and Km which increases. Mixed inhibition is very common and results from the formation of a complex consisting of the enzyme, the substrate, and the inhibitor that does not break down to products.

This sensitivity is easily understood when one considers that the essential catalytic groups are usually ionizable ones imidazole, carboxyl, amino fisiologia vegetal taiz that they are catalytically active in only one of their ionization states.

For example, imidazole acting as a base will be functional only at pH values above 7.

Eduardo Zeiger, Lincoln Taiz Fisiología vegetal. Volumen | Yamila Lopez -

Plots of the rates of enzyme-catalyzed reactions versus pH are usually bell-shaped, corresponding to two fisiologia vegetal taiz curves, one for an ionizable group acting as an acid and the other for the group acting as a base Figure 2.

Although the effects of pH on enzyme catalysis usually reflect the ionization of the catalytic group, they may also reflect a pH-dependent conformational change in the protein that leads to loss of activity as a result of disruption of the active site.

The temperature dependence of most chemical reactions also fisiologia vegetal taiz to enzyme-catalyzed reactions. Thus, most enzyme-catalyzed reactions show an exponential increase in rate with increasing temperature.

Fisiología vegetal

Mn Required for activity of some dehydrogenases, decarboxylases, kinases, oxidases, and peroxidases. Involved with other cation-activated enzymes and photosynthetic O2 evolution. Substitutes for potassium in some functions. Group 4 Nutrients that are involved in redox reactions Fe Constituent of cytochromes and nonheme iron proteins involved in photosynthesis, N2 fixation, and respiration.

Zn Constituent of alcohol dehydrogenase, glutamic dehydrogenase, carbonic anhydrase, etc. Cu Component of ascorbic acid oxidase, tyrosinase, monoamine oxidase, uricase, cytochrome oxidase, phenolase, laccase, and plastocyanin.

Ni Constituent of urease. Fisiologia vegetal taiz N2-fixing bacteria, constituent of hydrogenases. Mo Constituent of nitrogenase, nitrate reductase, and xanthine dehydrogenase.

After Evans and Sorger and Mengel and Kirkby Hydroponics fisiologia vegetal taiz used in the commercial production of many greenhouse crops.


In one form of commercial hydro- ponic culture, plants are grown in a supporting material such as sand, gravel, vermiculite, or expanded fisiologia vegetal taiz i. Nutrient solu- tions are then flushed through the supporting material, and old solu- tions are removed by leaching.


In another form fisiologia vegetal taiz hydroponic culture, plant roots lie on the surface of a trough, and nutrient solutions flow in fisiologia vegetal taiz thin layer along the trough over the roots CooperAsher and Edwards The vegetative body is composed of three organs: The primary function of a leaf is photosynthesis, that of the stem is support, and that of the root is anchorage and absorption of water and minerals.

Leaves are attached to the stem at nodes, and the region of the stem between two nodes is termed the internode.