Effects of supplement with sanitary landfill leachate in gas exchange of sunflower (Helianthus annuus L.) seedlings under drought stress

Abstract

Sanitary landfill leachate is one of the major problems arising from disposal of urban waste. Sanitary landfill leachate may, however, have use in agriculture. This study, therefore, aimed to analyze initial plant growth and gas exchange in sunflower seedlings supplemented with sanitary landfill leachate and subjected to drought stress through variables of root fresh mass (RFM), shoot fresh mass (SFM), total fresh mass (TFM), relative chlorophyll content (CL), stomatal conductance (g _s ), transpiration rate (E), net photosynthetic rate (A), ratio of internal to external CO₂ concentration (Ci/Ca),water use efficiency (EUA), instantaneous carboxylation efficiency (A/Ci), and electron transport rate (ETR). The experimental design was a completely randomized 2 (irrigated and non-irrigated) × 4 (sand, sand + 100 kg N ha^-1 organic fertilizer, sand + 100 kg N ha^-1 sanitary landfill leachate, and sand + 150 kg N ha^-1 sanitary landfill leachate) factorial with five replicates. Under drought stress conditions, leachate treatment supplemented with 100 kg N ha^-1 exhibited higher plant fresh weights than those of the treatment containing 150 kg N ha^-1. Increases in fresh mass in plant treatments supplemented with 100 and 150 kg N ha^-1 sanitary landfill leachate were related to higher photosynthetic rates.

Keywords: Drought stress; Gas exchange; Growth analysis; Helianthus annuus L.; Photosynthesis; Sanitary landfill leachate.