AbstractWhen apple leaves are momentarily dipped in a solution of a non‐deliquescent salt, significant amounts of copper, but not of magnesium, are taken up by the time that drying‐out of the surface deposit causes uptake to cease. If treated leaves are dipped again in copper sulphate solution, more copper is taken up in another period of rapid adsorption. Thus the initial adsorption process must play an essential part in all subsequent uptake. It is further shown that the greater part of the leaf surface must take part in the uptake process.Leaves momentarily dipped in a solution of a deliquescent magnesium salt (e.g. the chloride) usually take up significant amounts of magnesium within the first hour or so after treatment, but then uptake ceases. It is shown that normally only part of the leaf surface is able to take up magnesium.It is suggested, therefore, that more routes are available to copper than to magnesium (and urea) for entry into the l
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