Interrelationships between the Nature of the Light Source, Ambient Air Temperature, and the Vegetative Growth of Different Species within Growth Cabinets

Publisher Website
Google Scholar
Abstract
The interacting effects within growth cabinets of the nature of the light source and the temperature of the ambient air on 14 parameters of vegetative growth have been examined for Gotsypium hirsutum, Helianthus annuus, Phaseolus vulgaris, and Zea mays. The comparisons were between fluorescent lighting and mixtures with tungsten lamps (17 and 26 per cent of the total wattage), adjusted to give 32 400 lx and covering six equally spaced and constant air temperatures from 10 to 35 °C. The relationships are highly complex. Species differ in their responses to the three light sources. Moreover, for some parameters, but only for some species, there are highly significant interactions between the nature of the light source and the temperature level. Part of this complexity is due to the varying growth potential of species at low and high temperatures but important contributing factors are the differences between the temperatures of the ambient air and the plant parts. Such disparities may be positive or negative and are greater for leaf as against root temperature. The divergencies are larger during the day and largest for leaf temperature. With the higher proportion of tungsten lamps the leaf day temperature ranges from 7.1 °C above an ambient temperature of 10 °C to 2.5 °C above 35 °C ambient. For fluorescent lighting the leaves are 2.8 °C above ambient at 10 °C and 2.5 °C below at 35 °C. When variations in the response are examined against the mean internal day temperature of the plant, for some parameters, but not others, differences between light sources are no longer evident. Here again the reactions of species differ. It is concluded firstly that if only ambient air temperatures are recorded errors will arise in the interpretation of the induced biological responses, and secondly that departures from the ambient air temperatures will be dependent on the design of the cabinet and the lighting system.

This publication has 0 references indexed in Scilit: