TOXIC EFFECTS OF COPPER IN RICE PLANTS. BARU, PANAMA. 1999.

Abstract

This study began on april 15, 1999, in the locality of La Esperanza, Baru District, Province of Chiriqui, Republic of Panama, with the objective of determining concentrations of copper and the toxic effect in rice plants. The experiment was located at 30 masl, within a zone of the Pacific Ocean Slope, 08° 24’ 20.6“ North Latitude and 83º 43” 27.6” West Longitude, affected by Bordeles Broth contamination. A rice nursery was established in 0.5 m height plastic drums with capacity of 16 lt; holes were made at the bottom of all drums and they were placed in the open field without any covering. All drums were filled with soil from an area of Progreso, District of Baru, free of copper contamination. Treatments (microplots) were distributed following a Completely Randomized Design and consisted in adding copper from Cu₄SO.5H₂O to soil in the drums, at ≤10, 250, 500, 750 and 1000 mg of copper/kg of soil. Rice plants of IDIAP 863 variety were sowed in each drum at a density equivalent to 113.62 kg/ha. Rice plants were harvested after 120 days from microplots establishment. The analysis of copper in plant tissues showed copper concentrations of 1847.6 mg/kg in roots, a maximum of 4.8 mg/kg in stem and leaves combined samples, with the lowest values found in panicles (1.9 mg/kg). Experimental variables as plant height, total amount of kernels per plant, total amount of filled kernels per plant, total amount of empty kernels per plant, the amount of panicles per plant, and the amount of kernels per panicle were negatively affected by copper concentrations above 500 mg/kg of soil. Symptoms like yellowing and poor plant vigor were observed as copper concentrations in soil were increased.