Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

198
K. Janardhan Reddy
Manganese-deficient plants contained low levels of soluble carbohydrates.
The decrease is more in roots and this may be responsible for the reduced growth of
roots (Marcar and Graham, 1987). Mn 2+ deficiency induced the accumulation of soluble
nitrogen whereas the protein content was more or less same in Mn 2+ deficient and
sufficient plants (Table 8).
Table 8. Effect of manganese on growth and
certain chemical constituents of bean plants*
Parameter Leaves Roots
+Mn -Mn +Mn -Mn
Dry weight (g/plant) 0.64 0.46 0.21 0.14
Soluble carbohydrates
(mg/g. dry weight) 17.50 4.00 7.60 0.90
Soluble Nitrogen
(mg/g. dry weight) 6.80 11.90 17.20 21.70
Protein Nitrogen
(mg/g. dry weight) 52.70 51.20 27.00 25.60
*Adapted from Vielemeyer et al. (1969).
Manganese deficiency is common in soils with high pH and is also found in
highly leached tropical soils. Mn deficiency symptoms first appear in younger leaves.
The symptoms will vary from species to species. In monocots, greenish grey spots are
seen in the basal leaves, resulting in chlorotic striping between the veins. The deficiency
symptoms in oat is commonly referred as “grey speck” of oats. In dicots, initially small
yellow spots are visible and later on develops in to interveinal chlorosis. The deficiency
symptoms of Mn in certain crops were given specific names such as ‘marsh spot of
peas’, ‘grey speck of oats’ and pahala blight of sugar cane’. Ohiki et al., (1981) reported
critical deficiency level for most plant species in the range of 10-20 µg/g of dry matter.
Unlike the narrow range of manganese deficiency, the toxicity content varies
between plant species and environmental conditions. The critical toxicity content range
vary from 200 ppm in maize to 5300 ppm in sunflower (Table 9).