Phytochrome-induced Increase of Fluorescein Translocation in Mung Bean Hypocotyls

Abstract

Moderate doses of red (660 nanometer) irradiation cause a rapid increase in the translocation of fluorescein in dark-grown mung bean hypocotyl ( Vigna radiata L.) segments. The increase fails to appear following large doses of red (660 nanometers Consequently, by using fluorescein as a probe, it might be possible to obtain information which could lead to a better understanding of the mechanism of the action of light on some physiological processes. In this paper, some data are presented which suggest that red light has a rapid effect on the translocation. The reversal of the red light effect by far red light indicates the participation of phytochrome in the photoprocess. MATERIALS AND METHODSMung beans ( Vigna radiata L., cv. Oklahoma 612) seeds were screened for uniformity in size, spread over cheesecloth supported by a stainless steel wire screen over 5 liters of aerated tap water, and placed in darkness at 25 C. Four days later, seedlings growing upright were selected in dim green light at 25 C. The top 1.5 cm of a seedling was cut off, and the next 5-cm section was excised and used for experimentation. Seedlings and hypocotyl sections were handled gently and without pressure. Ten of the hypocotyl sections were placed apical end downward and vertical in a glass vial (1.4 x 4 cm) containing about I ml of distilled H20. The sections were then irradiated from above with narrow bands of red or far red light for various times. The light source was a 300-w projection lamp. White light from it was first passed through 9 cm of flowing water and then through interference filters (Ditric Optics, Inc.'). Bandwidths were 11.6 nm at 660 nm and 12.9 nm at 730 nm. The irradiance was 65 Aw/cm2 at 660 and 90 IAw/cm2 ' Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable. RESULTSThe effects of increasing length of exposure to red radiation on the translocation of fluorescein in mung bean hypocotyl section are depicted in Figure 1. Each data point is the mean of 150 measurements. After 5 to 40 sec of irradiation, red light significantly increases the movement of fluorescein in the hypocotyl sections. However, increasing the time of exposure beyond 60 sec results in nullification of the red induced increase.The red induced increase in fluorescein translocation is apparently controlled by phytochrome. Supporting data for phytochrome involvement in the photoprocess are presented in Figure 2. There is no increase if a 10-sec red exposure is immediately followed by a 15-sec far red exposure. Reversibility can be shown for at least two cycles. The difference between any final red and any final far red treatment is significantly different. DISCUSSIONRed light has been reported by Huisinga (4) to reduce the transport of fluorescein in mesocotyls of Avena seedlings. In contrast, results of this study show that a rapid increase o...

THE EFFECT OF TEMPERATURE ON PHYTOCHROME CONTROLLED HYPOCOTYL EXTENSION IN SINAPIS ALBA L.

“…Most laboratory work on photomorphogenesis is carried out at one standard temperature -25 °C (e.g. Hartmann, 1966;Mohr, 1972;Pike and Briggs, 1972; Oelze-Karow and Mohr, 1973Mohr, , 1974Quail, Schafer and Marme, 1973;Racusen, 1976;Brownlee and Kenrick, 1977;Jose and Vince-Prue, 1977;Wildermann et al, 1978;Tanada, 1978;Smith, Evans and Hilton, 1978;Hunt and Pratt, 1979;Jabben, 1980;Johnson, 1981, etc.). Everyday experience of the British climate, on the other hand, suggests that this is quite unrepresentative of the natural environment.…”

The Influence of Light Quality on Carbohydrate Translocation Within Corn Leaf Strips

“…Far-red light treatment leading to reversion to Pf would inhibit unloading. Tanada (1978) showed that in mung bean hypocotyls, Pfr stimulated translocation of fiuorescein, a negatively charged molecule. He suggested that this was due to the creation of a positive charge on the membrane.…”

“…Harper, Austin and Smith (1970) using a similar system have shown that red light photoreversibly stimulates transport of "C-labelled phenylalanine and cinnamic acid into pea terminal buds. Tanada (1978) demonstrated that red light photoreversibly promotes an increase in the translocation of fluorescein in mung bean hypocotyl segments.…”