Rapid Suppression of Growth by Blue Light

Abstract

The inhibition of stem elongation in dark-grown seedlings by blue Light was studied with marking techniques and with a high-resolution, growthmeasuring apparatus. Blue light rapidly suppresses growth in a variety of cultivated species. In some species, the inhibition persists only during the period of irradiation, after which time growth quickly returns to the high dark rate, whereas, in other species, the light response has an additional long-term component which lasts for at least several hours in the dark. The long-term inhibition may be mediated by phytochrome, whereas the rapid, short-term component is specific to a blue-light receptor.The rapid inhibition of growth in cucumber (Cucumis sativus L.) requires high-energy blue irradiation, which is perceived directly by the growing region of the hypocotyl and inhibits all regions below the hook to the same extent. Detailed investigation of the kinetics of the inhibition in cucumber and in sunflower (Heliantiws anus L.) shows that, after a short lag period (20 to 30 seconds in cucumber, 60 to 70 seconds in sunflower), the growth rate declines in an exponential fashion to a lower rate, with a half-time of 15 to 25 seconds in cucumber and 90 to 150 seconds in sunflower. Excision of the hypocotyl greatly reduces the sensitivity of the growth rate to blueUght inhibition. Because of the rapid kinetics, the blue-Ught photoreceptor cannot affect celi enlargement by altering the supply of growth hormone or the sensitivity to hormones but probably operates more directly either on the biochemical process which loosens cell walls or on celi turgor.

A reduced xylem pressure altered the electric and growth responses in cucumber hypocotyls

“…Accordingly, a lowered P^ (and turgor pressure) should increase the sensitivity of H"^ pumps and result in a second cut being more effective in reducing the GR and depolarizing the hypocotyl cells than the first cut. Other data support this proposal by showing that excision, a reduced xylem, and turgor pressure affect the sensitivity of H"*" pumps and growth to different stimuli such as wounding (this paper), auxin (Rubinstein 1977(Rubinstein , 1982Peters & Felle 1991) and light (Cosgrove 1981). Such a sensitivity change modifies the physiological responses of cucumber seedlings to environmental influences, including light, mechanical stimuli, soil water stress and herbivore attacks (Talamy & McCloud 1991).…”

“…The root plus 20 mm of the hypocotyl base was incubated in a vial with Hoagland solution of 0-1 strength. The hypocotyl hook of the cucumber seedling was connected to a displacement transducer and analogue integrator to measure the growth rate (Cosgrove 1981). The middle part of the seedling was fitted into a recording chamber (like the one described in Fig.l of Stahlberg & Cosgrove 1994).…”

Genetic Analysis of the Role of Gibberellin in the Red Light Inhibition of Stem Elongation in Etiolated Seedlings

“…Standard errors were in the same range for all the other genotypes used in this study except for the three slowest growing genotypes (L8 1, NGB5865, and NGB5862) where the SE were greater in proportion to the growth rates. Individual seedlings did not grow at a smooth constant rate, as other investigators measuring growth at high resolution have also noticed (3,5,13). Variations in growth rate from 10 to 20% during a 10 h recording of growth in darkness were not uncommon.…”

Growth Profile of Chamaedorea cataractarum (Cascade Palm) Seedlings with Different Colored Plastic Mulch

“…Gordon et al (2008 and observed no significant differences between blue and red plastic mulch for plant height and fruit yield in squash (2008) and okra (2010). Blue light is known to inhibit apical dominance in plants (Cosgrove, 1981;Mortensen and Stromme, 1987;Appelgren, 1991;Oyaerta et al, 1999;Runkle, and Heins, 2001;Muleo and Morini, 2008); however, a complex interaction of light induced effects regulates the response. The ratio of FR:R light can effect growth.…”