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

200
K. Janardhan Reddy
zinc deficiency and causes the decrease of protein content (Obata and Umebayashi,
1988). Zinc-deficient plants contained low levels of RNA. This may be due to higher
activity of ribonuclease (Sharma et al., 1982). Low protein content in zinc deficient
plants can be attributed to reduced levels of RNA (Cakmak et al., 1989). A close correlation
between the zinc supply and nitrogenous fractions and RNA content was observed
(Table 10).
Zinc deficiency is common in plants growing in highly weathered acid soils
and calcareous soils. Higher phosphate levels also induce zinc deficiency. The most
important symptoms of zinc deficiency include rosetting – stunted growth due to shortening
of internodes, little leaf – decrease in size of leaves and die-back – death of shoot
apices generally under severe deficiency of zinc. Interveinal chlorosis and necrosis
observed in older leaves of zinc-deficient plants.
Zinc toxicity induces stunted growth, interveinal chlorosis in young leaves,
which later on become dry and papery. Sometimes the affected leaves show the rolling
of leaf margins. Roots turn brownish and necrotic. The critical toxicity levels in leaves
of crop plants are 100 mg to 300 mg/g dry weight (Ruano et al., 1988).
Zinc uptake by crops is < 0.5 kg/ha/year. The deficiency could be corrected by
spraying zinc salts like ZnSO 4
or by soil application of zinc chelates.
Table 10. Effect of zinc on soluble nitrogen, protein nitrogen and
RNA content of two varieties (CV.) of Cicer arietinum L *
CV. Zinc Soluble nitrogen Protein nitrogen Soluble nitrogen RNA
conc. mg/g FW mg/g FW as % of total mg/g FW
(ppm) of leaves of leaves nitrogen of leaves
S1 S2 S3 S1 S2 S3 S1 S2 S3 S1 S2 S3
L-550 0 2.19 2.29 2.90 3.73 3.62 2.80 32.0 35.1 46.2 6.35 6.24 4.46
0.011 1.96 1.85 2.44 4.74 5.21 4.45 25.7 23.0 31.5 7.64 8.78 6.82
0.11 1.80 1.65 2.28 5.34 5.90 5.14 22.1 19.1 27.6 8.28 9.34 7.30
0.22 1.78 1.57 2.31 5.50 6.02 5.16 21.6 18.2 27.7 8.26 9.43 7.24
1.1 2.01 2.31 2.73 4.62 4.73 3.72 27.2 28.7 33.7 7.24 7.40 5.25
0 2.32 2.38 2.92 3.56 3.36 1.73 35.6 37.5 56.6 6.12 5.85 3.72
0.011 1.80 1.85 2.37 5.14 5.32 3.96 23.3 23.0 33.5 8.20 8.52 6.43
G-130 0.11 1.73 1.76 2.24 5.67 5.81 4.43 21.0 20.8 29.9 8.65 9.01 6.82
0.22 1.70 1.82 2.29 5.72 5.83 4.28 20.4 21.2 31.1 8.76 8.98 6.75
1.1 2.07 2.17 2.73 4.30 3.86 1.76 29.4 32.6 53.5 7.04 6.14 3.81
*Adapted from Reddy and Rao (1979).
Mean square values on the basis of analysis of variance significant at 5% level
S1=Pre-flowering stage, S2=Flowering stage, S3=Post flowering stage