Effect of Root-Zone Temperature on Growth and Quality of Hydroponically Grown Red Leaf Lettuce (Lactuca sativa L. cv. Red Wave)

Masaru Sakamoto,Takahiro Suzuki

doi:10.4236/ajps.2015.614238

Abstract

Soil temperature influences crop growth and quality under field and greenhouse conditions; however, precise investigation using controlled cultivation systems is largely lacking. We investigated effects of root-zone temperatures on growth and components of hydroponically grown red leaf lettuce (Lactuca sativa L. cv. Red Wave) under a controlled cultivation system at 20&degC. Compared with ambient root-zone temperature exposure, a 7-day low temperature exposure reduced leaf area, stem size, fresh weight, and water content of lettuce. However, root-zone heating treatments produced no significant changes in growth parameters compared with ambient conditions. Leaves under low root-zone temperature contained higher anthocyanin, phenols, sugar, and nitrate concentrations than leaves under other temperatures. Root oxygen consumption declined with low temperature root exposure, but not with root heating. Leaves of plants under low rootzone temperature showed hydrogen peroxide production, accompanied by lipid peroxidation. Therefore, low temperature root treatment is suggested to induce oxidative stress responses in leaves, activating antioxidative secondary metabolic pathways.

Highlights

Plant growth and development are influenced by various environmental factors, including light, temperature, How to cite this paper: Sakamoto, M. and Suzuki, T. (2015) Effect of Root-Zone Temperature on Growth and Quality of Hydroponically Grown Red Leaf Lettuce
Top and root fresh weights were reduced by low root-zone temperature treatment from those of the plants with ambient conditions (Table 2)
Suboptimal root-zone temperature tends to restrict plant growth, responsiveness to root-zone temperature depends on the plant species [45]

Summary

Introduction

Plant growth and development are influenced by various environmental factors, including light, temperature, How to cite this paper: Sakamoto, M. and Suzuki, T. (2015) Effect of Root-Zone Temperature on Growth and Quality of Hydroponically Grown Red Leaf Lettuce Plant growth and development are influenced by various environmental factors, including light, temperature, How to cite this paper: Sakamoto, M. and Suzuki, T. CO2, water supply, and pathogens [1]-[5] These often trigger plant abiotic and biotic stress responses, including secondary metabolites production, which plays a key role in stress resistance [6]-[8]. Higher levels of secondary metabolite generation may promote environmental stress tolerance, additional secondary metabolite production needs the energetic costs of synthetic processes, and these costs result in decreased plant growth and development [9] [10]. Constitutive biotic stress-responding mutant plants showed decreased plant size because of the activation of salicylic acid-mediated plant resistance responses, including antimicrobial secondary metabolites production [5]. To increase plant metabolite production by controlling their growth environment, suppressive effects on plant growth caused by environmental stresses must be considered

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Conclusion