Thus far, specific acetogenins in graviola and/or extracts of graviola have been reported to be selectively toxic in vitro to these types of tumor cells: lung carcinoma cell lines; human breast solid tumor lines; prostate adenocarcinoma; pancreatic carcinoma cell lines; colon adenocarcinoma cell lines; liver cancer cell lines; human lymphoma cell lines; skin cancer cell lines, and multi-drug resistant human breast adenocarcinoma.
In respiration energy is released fromsugars when electrons associated with hydrogen are transported to oxygen (theelectron acceptor), and water is formed as a byproduct. The mitochondriause the energy released in this oxidation in order to synthesize ATP. Inphotosynthesis, the electron flow is reversed, the water is split (not formed),and the electrons are transferred from the water to CO2 and in theprocess the energy is used to reduce the CO2 into sugar. Inrespiration the energy yield is 686 kcal per mole of glucose oxidized to CO2,while photosynthesis requires 686 kcal of energy to boost the electrons from thewater to their high-energy perches in the reduced sugar -- light provides thisenergy.
Boron deficiency affects the young growing points first, e.g., buds, leaf tips and margins, and root tips. Buds develop necrotic areas and leaf tips become chlorotic and eventually die. Tomato leaves and stems become brittle. Healthy leaves contain 20 to 100 ppm B; levels higher than 150 ppm may lead to toxicity. Cole crops, beets, and celery have rather high B requirements, otherwise only small amounts of B are needed by plants and supplying excessive B from fertilizer or from foliar sprays can lead to toxicity.
Iron is not mobile in plants and symptoms appear on the new leaves first. Symptoms consist of interveinal chlorosis that may progress to a bleaching and necrosis of the affected leaves. Usually, the chlorosis begins on the lower part of the leaflets and not at the tips. Normal leaves contain 30 to 150 ppm Fe on a dry-weight basis.
Calcium is immobile in the plant, therefore, deficiency symptoms show up first on the new growth. Deficiencies of Ca cause necrosis of new leaves or lead to curled, contorted growth. Examples of this are tipburn of lettuce and cole crops. Blossom-end rot of tomato also is a calcium-deficiency related disorder. Cells of the tomato fruit deprived of Ca break down causing the well-known dark area on the tomato fruit. Sometimes this breakdown can occur just inside the skin so that small darkened hard spots form on the inside of the tomato while the outside appears normal. On other occasions, the lesion on the outside of the fruit is sunken or simply consists of a darkening of tissue around the blossom area.
Potassium is absorbed in large quantities by an active uptake process. Once in the plant, K is very mobile and is transported to young tissues rapidly. Deficiency symptoms for K show up first on lower leaves as flecking or mottling on the leaf margins. Prolonged deficiency results in necrosis along the leaf margins and the plants can become slightly wilted. Deficient plant leaves usually contain less than 1.5% K. Deficiencies of K lead to blotchy ripening of tomatoes where fruits fail to produce normal red color in some areas on the fruit.
Nitrogen is absorbed as NH4+ and NO3 -. It is a mobile element in the plant and deficiency symptoms therefore show up first on the lower leaves. Symptoms consist of a general yellowing (chlorosis) of the leaves. On tomatoes, there might be some red coloration to the petioles and leaf veins. If the problem persists, lower leaves will drop from the plant.
Manganese functions in several enzymatic reactions that involve the energy compound adenosine triphosphate (ATP). Manganese also activates several enzymes and is involved in the processes of the electron transport system in photosynthesis.
Potassium plays a major role as an activator in many enzymatic reactions in the plant. Many enzymes responsible for cellular reactions require K as a co-factor. Another role for K in plants occurs in special leaf cells called guard cells found around the stomata. By regulating the turgor pressure in the guard cells, the degree of opening of the stomata is controlled and thus the level of gas and water vapor exchange through the stomata is regulated. Turgor is largely controlled by K movement in and out of guard cells.
Chlorine is supplied for plant nutrition as the chloride ion and is required in very small amounts for normal plant growth. Chloride is involved in photosynthesis and functions as a counter-ion in maintaining turgor pressure in cells. Chlorine deficiency symptoms are not common but include wilting. The chloride ion is very common in the environment and is often found as a constituent in fertilizers; therefore, deficiency symptoms are rare. High concentrations of chloride in the nutrient solution can be toxic to plants in hydroponic culture.
In contrast, ATP hydrolysis by the chloroplast ATP syn-thase in the dark has no physiological role and would be wasteful. In fact, the rate of ATP hydrolysis by the ATP synthase in thylakoids in the dark is less than 1% of the rate of ATP synthesis in the light. Remarkably, within 10-20 msec after the initiation of illumination, ATP synthesis reaches its steady-state rate. Thus, the activity of the chloroplast ATP synthase is switched on in the light and off in the dark. In addition to being the driving force for ATP synthesis, the electrochemical proton potential is involved in switching the enzyme on. Structural perturbations of the enzyme induced by the proton potential overcome inhibitory interactions with bound ADP as well as with a polypeptide subunit of the synthase. An additional regulatory mechanism that is unique to the chloro-plast ATP synthase is reductive activation. Reduction of a disulfide bond in a subunit of the chloroplast ATP synthase to a dithiol enhances the rate of ATP synthesis, especially at physiological values of the proton potential. The electrons for this reduction are derived from the chloroplast electron transport chain.
where n is the number of protons translocated per ATP synthesized, probably three or four, and a and b refer to the opposite sides of the coupling membrane. Provided the electrochemical proton potential is high, the reaction is poised in the direction of ATP synthesis. In principle,when the proton potential is low, ATP synthases should hydrolyze ATP and cause the pumping of protons across the membrane in the direction opposite that which occurs during ATP synthesis. ATP-dependent proton transport by the ATP synthase is of physiological significance in E. coli under anaerobic conditions in that it generates the electrochemical proton potential across the plasma membrane of the bacterium. This potential is used for the active uptake of some carbohydrates and amino acids.
Samples are often contaminated by fungicides, nutrient sprays, soil, or dust. Data obtained from contaminated leaf samples will be misleading. Decontamination of some dust or soil is best accomplished by quickly rinsing in a dilute non-phosphate detergent solution (2%) followed by two distilled water rinses. Tap water should not be used because it can be high in certain nutrients such as Ca, Fe, Mg, or S. Leaf samples should be washed quickly to minimize the leaching of certain nutrients (especially K) from the leaves. When testing for Fe, it is always necessary to wash the tissue as described above. It is not likely that contamination from chemical or nutrient sprays can be effectively removed from the leaf surface.