No abstract

Temperature affects the total amount, the time course, and the red/ far-red effectiveness ratio of light-dependent anthocyanin production in Brassica oleracea L. seedlings. Some of the effects of temperature on anthocyanin production in cabbage are in agreement with the predictions of a model proposed by JK Wall and CB Johnson (1983 Planta 159: 387-397) for the effects of temperature on the state of phytochrome and on the expression of phytochrome-mediated high irradiance responses, but others are not. The lack of a complete agreement between experimental results and model predictions might be due to factors related to the experimental system used or to limitations of the model or both.Light-dependent anthocyanin production in young seedlings displays properties typical of HIR2 plant photomorphogenic responses (8,9). Phytochrome is involved in the photoregulation of the HIR (9).Several theoretical models of phytochrome dynamics (2-4, 7, 15, 19) have been developed to explain the HIR in terms of the interaction between photochemical (photoconversion) and nonphotochemical (synthesis, destruction, dark reversion) reactions of phytochrome. In the range of temperatures from 0 to 30°C, phytochrome photoconversion is temperature-independent and the dark reactions are temperature-dependent: for example, the Qlo for phytochrome destruction is about 3 between 5 and 25C (13). Recently, Wall et al. (20) MATERIALS AND METHODSSeeds ofcabbage (Brassica oleracea L., Burpee Red Acre) were sown in Petri dishes on filter paper moistened with distilled H20.For the continuous irradiation treatments (Fig. 1), the seedlings were grown in darkness for 72 h at 14 or 25°C and then exposed 'Partially supported by National Science Foundation grants PCM-8008747 and DMB-8421 187 to A. L. M.

No abstract

No abstract

Anthocyanin production in cabbage (Brassica oleracea L.) and tomato (Lycopersicon esculentum Mill.) seedlings exposed to prolonged irradiations was studied under conditions that allowed discrimination, within certain limits, between the contribution of cryptochrome and phytochrome in the photoregulation of the response. The results of the study provide confirming evidence for the involvement of cryptochrome and direct evidence for a significant contribution of cryptochrome to the fluence rate dependence of the response to blue. The results provide some preliminary, direct indication for an interaction between cryptochrome and phytochrome in the photoregulation of anthocyanin production in seedlings exposed to the prolonged irradiations required for a high level of expression of the response. The type and degree of interaction between the two photoreceptors vary significantly, depending on the species and experimental conditions. Light-dependent anthocyanin production requires prolonged exposures to relatively high fluence rates of visible and near-visible radiation for a high level of response expression (10, 11). The extent of the response is a function of light quality, fluence rate, and exposure duration; action peaks have been found in the UV, BL,3 R, and FR spectral regions. The relative efficiencies of these regions vary significantly, depending on the species and experimental conditions (10,11).Anthocyanin production and other plant photomorphogenic responses to prolonged R and FR irradiations are mediated by phytochrome (10,11,16 acting or acting independently of one another (2,7,(19)(20)(21)24).The unknown nature of the UV-B-photoreceptor and cryptochrome and the fact that UV and BL excite not only these two photoreceptors, but also phytochrome, complicate studies on photoreceptor involvement and interaction in the mediation of responses to UV and BL (7,14). The selection of light treatments that can be used to discriminate the action of different photoreceptors is based on criteria ( 18,24) that take into account the differences between the known (phytochrome) and the inferred (cryptochrome and UV-B-photoreceptor) spectral properties of the photoreceptors.Both cryptochrome and phytochrome are involved in the photoregulation of anthocyanin production in young seedlings of cabbage (Brassica oleracea L.) and tomato (Lycopersicon esculentum Mill.) exposed to prolonged irradiations. Phytochrome involvement has been known for a long time (10, 11). Evidence for cryptochrome involvement (25) was obtained recently: BL was found to be significantly more effective than RF (a mixture of R and FR containing no BL) under conditions in which BL and RF maintained the same state of phytochrome in terms of P, k, and H ((PBL = (PRF, kBL = kRF, and HBL = HRF). Since RF excites phytochrome, but not cryptochrome, and BL excites both photoreceptors, the differences in anthocyanin production between BL and RF treatments that maintain the same state of phytochrome can be reasonably attributed to an involvement of crypt...