Page 31 - Volume 1, Issue 2, July 2008

Effects of Mg supply on “Colt” cuttings 83
and roots increased significantly (P<0.001)
with increasing external supply of Mg (Fig-
ure 2). There was a continuous decrease in
the [Mg] in leaves, whereas, the [Mg] in
shoots and roots were stable. At all levels
of Mg supply, there were a decline in [Mg]
in stems from transplanting until 30 DAP
and a continuous increase thereafter.
Symptoms of Mg deficiency occurred
on the lower leaves of the new shoots and
progressed towards the apical leaves of the
plants supplied with 0 and 150 μmol Mg l -1.
At the last harvest (92 DAP), Mg deficiency
symptoms appeared also on the basal leaves
of the plants supplied with 1500 μmol Mg
l-1. The symptoms included an interveinal
or marginal orange or yellow brown necro-
sis (often surrounded by a thin band of pur-
ple or pale green tissue) which spread over
most of the leaf blade; all the leaves became
tattered and curled upwards along the mid-
rib, and abscised soon after (Figure 3).
Potassium, Calcium, Nitrogen and Phosphorus
The [K] in leaves, stem, new shoots
and roots were not affected (P>0.05)
by the external supply of Mg (Figure
4) and, therefore, only the means of
Figure 4. The effect of Mg external supply on the [K] in leaves, stems, new shoots and roots of ”Colt”.
Figure 3. Symptoms of Mg deficiency in “Colt” leaves.