Water Relations

Water relations in higher plants under stress have mainly been investigated in connection with high NaCl concentrations in the submolar or even molar range (Ernst 2004). Concentrations of heavy metals are relevant in the submillimolar or even submicromolar range. Thus, direct osmotic effects can be excluded. Some of the effects mentioned here are common to many heavy metals, such as an influence on membrane transport and an inhibition of root growth and enzyme activities. Early effects may be weakly or strongly connected with water relations. It is relevant to focus here solely on the role of stomata and possible effects of heavy metals. In contrast to earlier results, it is now assumed that the primary effects of heavy metals in whole plants are not directly connected with the induction of stomata closure, but that early effects in roots (e.g. disturbed nutrient absorbance) may be responsible for changes in transpiration (Poschenrieder and Barcelo 2004). In some experiments with both high and low concentrations of heavy metals, enhanced transpiration has been measured. The reason for this is not clear, but it may be caused by damage to the cuticula. In most investigations, however, the application of heavy metals increased the stomatal resistance and in this way decreased the rate of transpiration. It is assumed that stomatal closure after the application of heavy metals is a consequence of stress due to water deficiency. This was concluded from the increased levels of proline and abscisic acid that have been measured, since both are known indicators of drought stress. Proline is evidently not involved in metal detoxification but in membrane stabilisation: K+ loss and lipid peroxidation were reduced after pretreatment with proline.

New experimental results (see references in Poschenrieder and Barcelo 2004) have revised the old concepts that (i) heavy metals have a direct effect on stomata closure and (ii) that the roots simply act as an osmometer, producing a hydraulic signal. Instead, roots can influence the water content via chemical signals, especially abscisic acid. Moreover, water transport appears to be modulated by an impairment of aquaporins, which is one of the earliest responses to heavy metals in plants. Many well-described physiological (or toxicological) responses may not be direct effects but consequences of fast responses in the roots.

Body Detox Made Easy

Body Detox Made Easy

What exactly is a detox routine? Basically a detox routine is an all-natural method of cleansing yourbr body by giving it the time and conditions it needs to rebuild and heal from the damages of daily life and the foods you eat and other substances you intake. There are many different types of known detox routines.

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