Solutes distribution, plant tissue

We have studied the uptake, translocation and distribution of Cs, Sr and by sunflower, poplar and reed. Attention has been focused not only on the time eourse of uptake from a radioactive hydroponic solution, but also on the distribution of radioactivity across plant tissues. Sunflower has also been used to identify the influence of K", Ca " and NHq" on Cs and Sr uptake and aeeumulation, with the aim of evaluating the effect of these ions whieh are normally present in the soil. 

As we indicated earlier, diffusion in a solution is important for the movement of solutes across plant cells and tissues. How rapid are such processes For example, if we release a certain amount of material in one location, how long will it take before we can detect that substance at various distances To discuss such phenomena adequately, we must determine the dependence of the concentration on both time and distance. We can readily derive such a time-distance relationship if we first consider the conservation of mass, which is necessary if we are to transform Equation 1.1 into an expression that is convenient for describing the actual solute distributions caused by diffusion. In particular, we want to eliminate Jj from Equation 1.1 so that we can see how c depends on x and t. 

The water solubility of 0,0-diethyl-0-2-pyrazinyl phosphorothioate (zinophos, 12) is greater than that of both phosphoric acid esters discussed above. Its 0.1% saturated aqueous solution is readily distributed in the soil. It exerts its action by direct contact with the nematodes at the surface of the plants or in the plant tissues (Motzinger, 1961). 

Gther factors affecting REE distribution in plants are concentrations in solution culture, species differences and humidity with high humidity favouring La " uptake. High levels of La ions in plant tissue resulted in deposition of the element in many membrane bound compartments as well as a wide distribution in the cytoplasm (Peterson and Hull 1981b). 

It is well known that chemical compo.sition of rhizosphere solution can affect plant growth. Particularly, uptake of nutrients may be considerably influenced by the ionic concentration of the rhizosphere solution (40). Despite the difficulty of defining the exact concentration of ions in the rhizosphere surrounding each root (or even root portion), it has been unequivocally demonstrated that plants have evolved mechanisms to cope with the uneven distribution of ions in the root surrounding in order to provide adequate supply of each essential nutrient (41). These mechanisms include expression of transporter genes in specific root zones or cells and synthesis of enzymes involved in the uptake and assimilation of nutrients (40,43). Interestingly, it has been shown that specific isoforms of the H -ATPase are expressed in the plasma membrane of cell roots it has been proposed that the expression of specific isoforms in specific tissues is relevant to nutrient (nitrate) acquisition (44) and salt tolerance (45). 

The uptake of nutrients into plant cells as well as their distribution between organs and tissues is a prerequisite for growth, and it is generally accepted that transport demands the energization of the plasma membrane (plasmalemma), particularly in cases where transport is accomplished against the (electro-)chemical gradient of the solute in question. In plants the proton motive force... 

Cyanocobalamin is widely distributed in living organisms it is found in bacteria, in algae and in animal tissues, but it does not appear to be present in the green leaves of plants. For man, it is an important vitamin, being one of the extrinsic factors of haemopoiesis. It was crystallized in 1948 the crystals are dark red, melt at 320 and their solution has well pronounced absorption bands at 278, 361 and 550 m/i. It contains cobalt and phosphorous and the molecular weight is around 1,500. On acid hydrolysis, cyanocobalamin yields 5,6-dimethylbenzimidazole, ribofuranose, phosphoric add, l-amino-2-propanol and a cobalt complex in which the metal... 

Plant proteinases (cf. Table 2.22) and also those of microorganisms are utilized for ripening and tenderizing meat. The practical problem to be solved is how to achieve uniform distribution of the enzymes in muscle tissue. An optional method appears to be injection of the proteinase into the blood stream immediately before slaughter, or rehydration of the freeze-dried meat in enzyme solutions. 

It is well documented that, selenate is taken up by plant roots from soil solution by a process of active transport (Brown and Shrift 1982). It competes with sulfur for uptake, both anions using a sulfate transporter in the root plasma membrane (Arvy 1993). Organic forms of Se, such as selenomethionine, are also taken up actively by plant roots. In contrast, transport of selenite does not appear to require the use of a sulfur transporter (Abrams et al. 1990). Subsequent translocation of Se within the plant is related to the form in which the element is supplied to the root. Se04 is more easily transported from the roots and much more is accumulated in the leaves than either SeOs" or organic selenium. Much of the SeOs is retained in the roots where it is rapidly converted into organic forms, particularly selenomethionine (Zayed et al. 1998). Distribution of Se in various tissues differs between accumulator and nonaccumulator plants. In the former, the Se is accumulated especially in young leaves, but later appears at higher levels in seeds than in other tissues, while, in nonaccumulators, such as cereals, levels in seeds and roots are usually the same as reviewed by Reilly (2(X)6). 

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