Effects Of Light Levels Research Articles

Influence of environmental factors on social play behavior of juvenile rats

The effects of light level and familiarity to the testing environment on social behaviors related and unrelated to play were investigated in juvenile rats accustomed to dim light conditions. Pinning, a measure characteristic for social play in rats, was completely suppressed under intense light conditions. Following/chasing and boxing/wrestling, social behaviors related to play, were also decreased under intense light. Of the measures of social behavior not related to play, contact behavior was decreased under intense light whereas social exploration was hardly affected. Levels of social exploration and following/chasing gradually declined during the 15-min test period. Frequency of contact behavior decreased, whereas duration increased with time. Under dim light conditions, unfamiliarity to the test cage suppressed pinning and boxing/wrestling but not the other social behaviors in the first part of the test period. These findings show that social behavior in juvenile rats, as in adult rats, can be influenced by light level and familiarity to the test cage. Social behaviors related and unrelated to play seem to be differentially influenced by environmental stimuli.

Flowering of Anthurium following Treatment with Gibberellic Acid

Table 1. Effect of light levels and GA3 concentrations (applied as a single foliar spray) on the mean number of inflorescences produced by two Anthurium scherzeranum cultivars. The data presented are from two separate experiments. Anthuriums are becoming popular “flowering” foliage plants as growers look for new crops to expand their markets. Advantages of anthurium are that they can be grown in environments similar to many other foliage plants, liners from tissue culture are available year round, attractive inflorescences can be produced continually under greenhouse conditions, and new cultivars developed for pot culture are becoming available. Anthurium inflorescences are normally produced by a dominant central stem initially and later by lateral stems, if produced. Cultivars with many lateral shoots, while desirable for pot culture, tend to flower later than those with strong apical dominance. Stimulating earlier flowering of lateral shoots could result in shorter production time and higher flower counts. Therefore, the following experiments were conducted using gibberellic acid (GA3) in an attempt to increase flower production of anthuriums. GA3 was chosen because it has been used previously to stimulate flowering of several other ornamental aroids (Henny, 1980, 1981, 1983). The first experiment was conducted using 105 plants of A. scherzeranum ‘Amazone’, 28 weeks from tissue culture, ≈ 10 cm high, and growing in 10-cm-diameter (0.45-liter) pots filled with a 1 pine bark : 1 Vergro Container Mix A (v/v) (Verlite Co., Tampa, Fla.). Plants were placed in a randomized block design in a shaded greenhouse with a temperature range of 18 to 32C and 110 umol·m -2·s-1 maximum light intensity under natural photoperiod in Apopka, Fla. Plants were fertilized with 2.5 g of 19-6-12 (NP2O5-K2O) Osmocote per pot applied on the soil surface. Gibberellic acid (ProGibb, Abbott Laboratories, North Chicago) was applied at 0, 12.5, 250, 375, or 500 mg a.i./

Light Levels, Growth, and Essential Oil in Dill (Anethum graveolensL.)

The effect of light level on growth and development of dill herb was studied in a greenhouse under full sunlight and under 70, 50, and 30 percent of full sunlight. Decreasing light levels resulted in decreases in leaf number, leaf area, and plant height. Dill growth and essential oil accumulation increased with increases in the light level and was greatest under full sunlight.

Light, Leaf Expansion and Seed Yield in Sunflower

Two sunflower hybrids, Hysun 31 and Suncross 150, were grown in the field with adequate irrigation and given three light treatments throughout their life cycle. The treatments were 100, 50 and 20% sun (high, medium and low light); during the vegetative period the high light treatment averaged more than 20 MJ m-2 day-1 total short-wave radiation. The two cultivars, although differing in many of the leaf and plant growth parameters measured, followed the same trends with respect to light. A reduction from 100 to 50% light delayed the appearance of leaves slightly but had no effect on patterns of leaf-area expansion such as the rate and duration of expansion of individual leaves and the distribution of leaf area among nodes. A further reduction in light, however, significantly reduced the size of all leaves through effects on the rates at which leaves expanded. There was no effect of light level on the period for which leaves expanded. Whilst leaf expansion remained unaffected by a reduction from high to medium light, specific leaf weight was significantly reduced to 76% of control levels. The lowest light regime further reduced specific leaf weight to only 59% of control levels. Total plant weights declined to 89% (not significant) at the medium light level and significantly to 47% at the low level and as harvest index was marginally, though not significantly, decreased by a reduction in light, these values translated into significant reductions in seed production (86 and 44% of controls).