Influence of environmental stresses on response of bush bean plants to excess copper

Abstract

Bush beans (Phaseolus vulgaris L. cv. Improved Tendergreen) were grown in mtrient solutions in a glasshouse at low and at potentially toxic levels of Cu. These Cu treatments were interacted with other treatments to create various types of environmental stress. In an exploratory experiment, salinity (0.05M NaCl) and phosphorus deficiency stresses were observed to result in proportionately more plant toxicity with a high Cu level than with a low. These two factors were then further studied in additional experiments and the observations were verified. Levels of P and NaCl which resulted in no or little yield reduction with normal amounts of Cu resulted in proportionately large yield decreases at high levels of Cu. Stress resulting from no aeration of the nutrient solution was less harmful relatively at a high Cu level than at a low. Slightly increased root temperature was slightly more injurious at the high Cu level than at the low while severe shading was equally harmful of both Cu treatments. Synergistic effects were noted for salinity and phosphorus levels as they interacted with the copper levels on growth of the plants. Mineral analyses do not explain these synergistic effects.

Key words:

• Salinity
• phosphorus deficiency
• limiting factors
• copper toxicity
• root temperature
• stress
• shading
• sodium chloride