Optimal Light Level Research Articles

CONTROLLED IN VITRO ENVIRONMENT FOR STAGE II MiCROPROPAGATION OF BUDDLEIA ALTERNIFOLIA (BUTTERFLY BUSH)

ABSTRACT Optimal light, sucrose, and CO2 levels were determined for Stage II micropropagation of Buddleia alternifolia (Butterfly Bush). Five levels each of light (50, 75, 100, 125, 150 ixmol m-2s-l PPF), of sucrose (0, 1, 2, 3, and 4%), and of force-ventilated CO2 (0, 350, 600, 900, 1200 ppm) were compared through one-way factorial experiments. Three levels of each factor were then selected for a 3x3x4 factorial experiment of the same culture. Free-ventilated CO2 of 350 ppm, serving as control, constituted the fourth level of CO2. The results showed that the observed optimum points were 2% sucrose, 125 |xmol m-2s-l PPF, and 600 ppm force-ventilated CO2. Based on the lack of interactive effects between the factors, the general absence of statistical differences between the levels within each optimum factor range, and considerations of economic benefits, the preferred factor levels were chosen to be 3% sucrose, 350 ppm free-ventilated CO2, and 75 |imol m-2s-i PPF. The study also revealed that elevated in vitro light and CO2 levels, in the absence of sucrose, did not promote the growth of the culture.

FRUIT QUALITY DEVELOPMENT OF `GRANNY SMITH' APPLES IN RESPONSE TO TREE CANOPY LIGHT MICROCLIMATE.

A preliminary study suggested light distribution (400-700nm) did not change from terminal bud set (July) to harvest (9/9/88). Therefore, limbs of 5-year-old trees were shaded the last 90 days of the season in 1988 and 7-year-old trees were shaded the last 60 days in 1989 with 30, 63, 95% or no shadecloth. Medium (63%) and heavy (95%) shade decreased fruit weight both years. Fruit soluble solids (SSC) decreased with increasing shade in 1988 but not in 1989 until after 60 days of storage. Fruit peel chlorophyll (chl) declined with time for all treatments. Apples from full sun and heavy shade treatments had the lowest chl and visually appeared the lightest. Evidence from both years suggested there was an optimal light level between 37-70% full sun for maximum fruit color and chl. Link of 7-year-old trees were shaded at intervals, light all season, mid-season and late season. Fruit weight and firmness were not affected by time of shading. SSC was liner for mid-season shaded fruit. Chl was highest for late season shaded fruit but differences evaporated by 90 days of storage.

FRUIT QUALITY DEVELOPMENT OF `GRANNY SMITH' APPLES IN RESPONSE TO TREE CANOPY LIGHT MICROCLIMATE.

A preliminary study suggested light distribution (400-700nm) did not change from terminal bud set (July) to harvest (9/9/88). Therefore, limbs of 5-year-old trees were shaded the last 90 days of the season in 1988 and 7-year-old trees were shaded the last 60 days in 1989 with 30, 63, 95% or no shadecloth. Medium (63%) and heavy (95%) shade decreased fruit weight both years. Fruit soluble solids (SSC) decreased with increasing shade in 1988 but not in 1989 until after 60 days of storage. Fruit peel chlorophyll (chl) declined with time for all treatments. Apples from full sun and heavy shade treatments had the lowest chl and visually appeared the lightest. Evidence from both years suggested there was an optimal light level between 37-70% full sun for maximum fruit color and chl. Link of 7-year-old trees were shaded at intervals, light all season, mid-season and late season. Fruit weight and firmness were not affected by time of shading. SSC was liner for mid-season shaded fruit. Chl was highest for late season shaded fruit but differences evaporated by 90 days of storage.

COMPARATIVE GROWTH OF Isochrysis galbana PARKE AND Isochrysis aff. galbana, CLONE T‐ISO AT POUR TEMPERATURES AND THREE LIGHT INTENSITIES

AbstractThe growth of a temperate and a tropical strain of Isochrysis was studied at four temperatures and three light intensity levels. All algal cultures were grown in an enriched artificial seawater medium under constant illumination and were bubbled with air enriched with 0.1% CO2. Culture density (cells/ml) was measured periodically during exponential growth. Average growth rates for each combination of temperature and light intensity are presented as doublings/day. Observations of growth under the various culture conditions indicate that T‐ISO (tropical strain) grows rapidly over a much broader range of temperatures than does I. galbana. Variations in growth at different light intensity levels suggest that the optimum light level increases as a function of temperature for T‐ISO and that the growth of I. galbana is inhibited by high levels of light (1500 μW/cm2). The relative value of both strains as food for larval and juvenile oysters and the advantages and limitations of large scale culture are discussed.

Is There an Optimum Light Level for Office Tasks?

The data of these experiments involving office tasks do not support the hypothesis that there is an optimum light level above which performance deteriorates.