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Effects of Light Intensity, Temperature, and Root Gaseous Environment on Growth of Nicotiana tabacum L.¹

The response of Nicotiana tabacum L. plants to various gaseous treatments (O₂, CO₂, N₂) in the root environment was determined by microscopic examination of roots and measurements of stem diameter and leaf area. Superimposed on the gaseous treatments were three environmental energy input levels in which light intensity, air temperature, and nutrient solution temperature were varied. The plants were grown in an artificially lighted, controlled environment room with roots in an intermittent nutrient solution mist in airtight chambers. The roots were treated with gaseous mixtures for 24 hours and then returned to an atmosphere of air for a 5-day recovery period. Mixtures of 1% O₂ in N₂, with or without CO₂ present, reduced plant growth slightly at 1,000 ft-c light intensity and 18.3C day temperature, but these mixtures progressively decreased growth as light and temperature increased. At 1,000 ft-c light intensity and 18.3C day temperature a pure N₂ treatment inhibited growth of plants; however, plants slowly resumed growth during recovery. At 4,000 ft-c light intensity and 29.4C day temperature, N₂ treatments killed the root system. Data obtained from measurements of stem diameters, leaf area, root weights, and water use suggest that the survival and growth of plants subjected to poor soil aeration is largely dependent on the ambient temperature and light intensity.

Key Words: Drainage • Aeration • Oxygen deficiency

² Research Plant Physiologist, SWCRD, ARS, USDA, and Professor of Biological and Agricultural Engineering, North Carolina State University, Raleigh, N. C. 27607.

Received for publication August 19, 1968.