English

Silva Samuel,Do Nascimento Ronaldo,De Sousa Silva Sonivagno,Azevedo Xavier Diego,Alberto Ferreira Cardoso Jos Eacute,Oliveira Hallyson

doi:10.5897/ajar2016.10789

Abstract

The temperature of the nutrient solution in hydroponic crops of lettuce is a determinant of biomass yield and affects several physiological mechanisms of the plant. The aim of this study is to evaluate the influence of nutrient solution temperature on the levels of nitrate and pigments in leaves, as well as green mass yield and thermal flow in lettuce crop hydroponically. The experiment was conducted in a greenhouse at the Federal Technological University of Parana. The nutrient solution was maintained at three temperatures (15 and 25°C and environmental temperature). The accumulated nitrate in leaf and photosynthetic pigment level were evaluated five times (28, 35, 42, 49 and 56 days after sowing). The total green mass yield and thermal flow behavior in the plants were assessed through thermographic analysis. The temperature of the solution influenced the levels of nitrate, chlorophyll and carotenoids in lettuce leaves, and green mass, which were larger at 25°C treatment. The root and stem had thermal equilibrium with the nutrient solution, while the temperature at the middle and upper part of the plant is similar to that of the environment. Key words: Lactuca sativa, pigments, nitrate, heat conduction, green mass.

Highlights

Hydroponic is a production technique that allows the control of many variables
The aim of this study is to evaluate the influence of nutrient solution temperature on the levels of nitrate and pigments in leaves, as well as green mass yield and thermal flow in lettuce crop hydroponically
The total green mass yield and thermal flow behavior in the plants were assessed through thermographic analysis

Summary

Introduction

Hydroponic is a production technique that allows the control of many variables. With the current available technologies, it is of great benefit to conduct research that enables the maximization of productivity in this cropping system.Among the leafy vegetables that adapted more to this system, lettuce is mostly grown by farmers and consumed in Brazil because of its nutritional value, taste, and availability throughout the year (Geisenhoff et al, 2009). With the current available technologies, it is of great benefit to conduct research that enables the maximization of productivity in this cropping system. Among the variables that can be affected by the temperature of the solution, there is the absorption of nutrients (Feltrim et al, 2009). High transpiration flow carries more nutrients up to the leaves, mainly nitrogen (N) in nitrate form. With the satisfactory amounts of N accumulated in the leaves, the plant tends to produce more biomass and larger molecules formed by this element. The amount of nitrate in the leaves must be accompanied often, because its residuality is an indicator of it being toxic to human health as a potential carcinogen (Luz et al, 2008)

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