Effect of light quality on Tabebuia rosea seed germination

Abstract

Tabebuia rosea germination capacity and rate have been examined under light and dark conditions. However, seeds responses to light quality, in particular to short and mid-wavelengths, are not well known. We hypothesized that short wavelengths would have a positive effect on T. rosea germination. The effects of short, mid and long-wavelengths on germination capacity, rate (germination rate index, germination rate R50, a devised index of germination rate R50´ and peak value), mean daily germination and germination value were evaluated. Light quality had little effect on germination capacity; it was reduced only in darkness. Seeds under short and midwavelengths germinated faster (germination rate) than under any other light treatments. We concluded that although T. rosea seeds respond to all light quality treatments, the short and mid-wavelengths are the cue for increasing germination speed. For synchronizing germination, short and mid-wavelengths transmitted by red cellophane paper can be used as a pre-germinative treatment for restoration and silvicultural purposes.

Temperature and light under the physiological potential of seeds of Handroanthus impetiginosus

“…These results are in accordance with those of Bewley et al (2014), where the germination rates are highly sensitive for temperature, generally increasing till they attain ideal temperature and then decreasing drastically. Although the total percentage of germination reveals a broad spectrum of maximum temperature, it is possible to use the germination rates to accurately identify the ideal germination temperature.…”

“…The seeds subjected to 15°C and 40°C did not germinate, and were deteriorated at the end of the test (Figure 1). During germination at low (5-10°C) or extremely high (>45°C) temperatures, the metabolism is not appropriately activated, and the reserves deployed in phase I are necessary for the growth and development of the embryo in phase III and are not carried to the meristematic regions (BEWLEY et al, 2014). Thus, the germination remains incomplete, and the seeds do not pass beyond phase II.…”

“…The temperature interferes with the biochemical reactions that determine the germination process, thus influencing the capacity and speed of germination. Hence, seeds have the ability to germinate within a certain temperature range, characteristic for each species; however, the time required to reach the maximum percentage of germination is temperature dependent (BEWLEY et al, 2014).…”