Comparison of Photomorphogenic Responses to UV Light in Red and White Cabbage (Brassica oleracea L.)

Abstract

Photoinhibition of hypocotyl growth in white cabbage (Brassica oleracea L., cv "Bianco Brunswick") is controlled by UV absorbing receptor(s) and the phytochrome system, while in red cabbage (cv "Rosso Olandese tardivo invemale") phytochrome can act without any requirement for the action of a specific UV receptor. Similar results have been obtained for the photoregulation of anthocyanin production. Twenty-four hour preirradiations with UV light or 692 nanometers light lead to the same increase in responsiveness of the system toward Pfr in a following dark period, suggesting a phytochrome promotion of subsequent light induction for both.A considerable number of studies have been reported on the effects of UV radiation on higher plants (2,3,10,23). Nevertheless, the nature and the mode of interaction between the photoreceptors involved in the control of the photomorphogenic responses induced by UV irradiation, is still an open question. UV may induce both negative (damaging) and positive (nondamaging) effects in higher plants, and the same response can be differently affected (positively or negatively) depending on the fluence rate (1 1). UV light is absorbed by phytochrome, the red-far red reversible photoreceptor of plants, causing photoconversion of Pr to Pfr and vice versa, both in vitro (see 13 for the relevant literature) and in vivo (15). A specific blue-UV receptor known as cryptochrome, with one of its peaks at about 370 nm has been characterized by action spectroscopy (16). In addition, a little studied UV-

The Use of UV Radiation to Control the Architecture of Salvia splendens Plants. II. Relationships between PAR Levels and UV Radiation in the Photoregulation of Stem Elongation

“…According to the classical photobiological techniques the action spectra and the kinetics of the responses must be established in order to identify the causal factors involved in UV-mediated responses (8,9). Ultraviolet-induced inhibition of elongation growth has been shown in different species, so it appears to be a general phenomenon (5,7,(12)(13)(14)(15)(16)(17). In this work we have measured the short-and long-term stem elongation responses to UV radiation of S. splendens plants by using linear voltage transducers interfaced with data loggers.…”

PHOTOMORPHOGENIC RESPONSES TO UV RADIATION. II: A COMPARATIVE STUDY OF UV EFFECTS ON HYPOCOTYL ELONGATION IN A WILD‐TYPE AND AN aurea MUTANT OF TOMATO (Lycopersicon esculentum Mill.)

“…Previous studies on the effects of UV radiation, between 300 and 400 nm, on tomato and cabbage stem elongation (Lercari et al, 1989(Lercari et al, , 1990 have shown that the inhibitory effect of UV radiation, at high photon thence rates, can be completely ascribed in some cases to the action of phytochrome; in other cases to the action of both phytochrome and a specific UV photoreceptor; and in yet other cases to the action of only a UV photoreceptor. Studies on conifer species (Sullivan and Teramura, 1988) showed a fluence-dependent, UV-induced reduction of seedling height in Pinus contorta, Pinus *To whom correspondence should be addressed.…”

“…Since UV radiation induces phytochrome photoconversion (Butler et al, 1964;Lercari et al, 1989Lercari et al, , 1990 it is not possible with a single experimental approach to establish if the phytochrome system is involved or not in a UV-mediated response. In the present paper the involvement of phytochrome in the UV-mediated inhibition of hypocotyl elongation was studied using different experimental approaches: (a) by giving exposures of increasing duration to 692 nm and UV radiation, that are equivalent with respect to the phytochrome system (Lercari et al, 1989(Lercari et al, , 1990), (b) by giving various UV irradiations in which the UV spectral range was modified with specific cut-off filters.…”

How do UV Photomorphogenic Responses Confer Water Stress Tolerance?¶†

“…Inhibition of hypocotyl expansion in tomato (Lycopersicon esculentum Mill.) Although such reasoning provides a rationale for the adaptive significance of similar responses in other plants (15,16), it fails to explain positive phototropism induced by UV-B (17, and references therein). It has been hypothesized that low-level UV radiation may act as a signal that suppresses hypocotyl elongation, allowing tomato seedlings to develop a protective pigmentation before emerging into direct sunlight (14).…”