EFFECTS OF CALCIUM ON LIGNIFICATION RELATED PARAMETERS IN SODIUM CHLORIDE-STRESSED SOYBEAN ROOTS

Abstract

The effects of exogenous calcium (Ca²⁺) on root growth and lignification-related parameters – phenylalanine ammonia-lyase (PAL) and peroxidases (POD) activities, hydrogen peroxide (H₂O₂) and lignin contents – in roots of NaCl-stressed soybean seedlings were analyzed. Three-day-old seedlings were cultivated in half-strength Hoagland's solution (pH 6.0) with or without 5 mM calcium nitrate [Ca(NO₃)₂] and 50 to 200 mM sodium chloride (NaCl) in a growth chamber (25°C, 12/12 h light/dark photoperiod, irradiance of 280 μmol m⁻² s⁻¹) for 24 h. In general, results showed that the absence of Ca²⁺ reduced root growth and increased lignification of soybean seedlings grown in NaCl-free nutrient solution. NaCl reduced the root growth and all lignification-related parameters. Root growth, PAL and POD activities and hydrogen peroxide (H₂O₂) contents were more affected after NaCl treatments without Ca²⁺ in the nutrient solution. At 5 mM, Ca²⁺ did not alleviate the deleterious effects of NaCl on lignification-related parameters.

Keywords:

• calcium
• phenylpropanoid pathway
• roots
• salt stress
• soybean

ACKNOWLEDGMENTS

G. Y. S. Neves would like to thank CAPES (Brazil) for providing a scholarship. M. L. L. Ferrarese and O. Ferrarese-Filho are research fellow of CNPq (Brazilian Council for Scientific and Technological Development). The authors kindly thank Aparecida M. D. Ramos for her skillful technical assistance.