摘要:

Abstract—The physiological relationships between the effects of phytochrome photoequilibrium (Pfr/P) on internode extension growth and dry matter accumulation were investigated in white light (WL)‐grownSinapis albaL. seedlings. After 11 days under continuous WL, the seedlings were exposed: (a) to pulses of light providing different Pfr/P, followed by 24 h darkness (D); (b) to pulses of light providing different Pfr/P, followed by 3 h D and 24 h continuous WL; (c) to continuous WL with or without supplementary far‐red light (to reduce Pfr/P); or (d) to pulses of light providing different Pfr/P followed by D, in factorial combination with either water or a saturating (0.2M) sucrose solution applied to one of the leaves. In D (“a” and “d”) low, compared to high Pfr/P increased both internode extension growth and dry weight to the same extent. Under WL (“b” and “c”) low PfrlP promoted internode extension growth but had no proportional effects on internode dry weight. Sucrose promoted internode extension growth with a lag of at least 8 h (compared to the rapid effect of low Pfr/P) and did not reduce the effect of low Pfr/P. These results indicate that Pfr/P effects on internode extension growth are not the consequence of changes in photoassimilate translocation from the leaves. Under WL, PfdP effects on internode length occur partially at the expense of internode dry m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02204.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Cotton (Gossypium hirsutumL.) seedlings were morphologically responsive to red (R) and far‐red (FR) light (low and high FR/R photon ratios, respectively) from time of emergence. Controlled environment R and FR treatments confirmed phytochrome involvement in biomass allocation among new leaf, stem and root growth. Seedlings that received the high FR/R photon ratio developed longer and heavier stems, leaves with lower specific weights, less massive roots and higher shoot/root biomass ratios. Other cotton seedlings were grown in sunlight over different colored soils or painted panels to measure morphological effects of FR/R photon ratio in upwardly reflected light. Morphological responses to a given FR/R ratio were the same whether the reflection was from natural soil or from a painted surface. Seedlings that received the higher FR/R photon ratios in upwardly reflected light developed longer stems, leaves with lower specific weights, less massive roots and higher shoot/root biomass ratios. The potential use of colored mulches in agriculture was discus

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02205.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The spectrophotometric assay of phytochromein vivoin etiolated plant material was used to determine the effects of changes in reflected light on the state of the photoreceptor in etiolated seedlings exposed simultaneously to direct and reflected light. Changes in reflected light that were small in terms of the total (direct + reflected) radiation incident on the seedlings produced detectable changes in the state of phytochromein vivo. The contribution of reflected light to the state of phytochrome in vertical organs was greater than expected from its low contribution to total incident light. These data from laboratory studies complement and are consistent with results of field studies on the effects of light reflected from neighboring vegetation on plant growth under natural radiation condition

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02206.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The equation for phytochrome photoconversion, derived from photoconversion kinetics of purified phytochrome, predicts that the rates of photoconversions starting from low and high Pfr/Ptot(0), (initial Pfr/Ptot) should be the same for light of the same quality and fluence rate. The situation might be differentin vivo. Phytochrome photoconversion rates were measured in excised cotyledons ofCucurbita pepoL. exposed to BL (blue; ϕBL= 0.39; ϕ, Pfr/Ptot at photoequilibrium) and RI (mixture of red and far red; ϕRI= 0.46) after saturating preirradiations with red and far‐red to establish high (0.78) and low (0.02) Pfr/Ptot(0), respectively. Under BL, the rate of photoconversion is faster when starting from a high than a low Pfr/Ptot(0); under RI, the rate of photoconversion is faster when starting from a low than a high Pfr/Ptot(0)., No effects of Pfr/Ptot(0), on photoconversion rates were found in phytochrome solutions exposed to BL and RI. These data provide another indication of the discrepancies between phytochrome photconversion kineticsin vivoandin

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02207.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—A custom‐built modulated split‐beam spectrophotometer has been used to measure the absorbance of tissue samples and purified phytochrome whilst exposing the sample to actinic 633 nm laser radiation at fluence rates approaching those of daylight. This approach has allowed the direct observation of the accumulation of phytochrome photoconversion intermediates at high fluence rates. Atca1250 μmol m−2s−1upwards of 35% of the total phytochrome was present in the form of photoconversion intermediates in tissues of maize, sunflower and tomato. In other tissues tested (wheat, bean andAmaranthus) and in purified oat phytochrome, rather smaller levels of intermediates accumulated. Upon “lights‐off” only a proportion of the accumulated intermediates decayed to far‐red absorbing phytochrome (Pfr), the remainder appearing as the red‐absorbing form (Pr). Difference spectra suggested that, at high light levels, Pr may be reformedviaa photochemical back‐conversion of an intermediate in the Pr—Pfr pathway, although the involvement of intermediates in the Pfr—Pr pathway cannot be excluded. The implications of the results for the ecological function of

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02208.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstraet—Seedlings of wild type (WT) and thelhmutant ofCucumis sativuswere grown in white light and given supplementary far‐red radiation either to the whole plant, orviafiber‐optic probes directed at the apical region of the hypocotyl. In both WT and mutant seedlings, reducing the ratio of red to far‐red radiation resulted in significant increases in extension growth. Direct measurement of extension rate by transducer techniques revealed that the mutant seedlings responded to additional far‐red radiation by an increment in extension rate that was equivalent to that observed with the WT seedlings. Assuming that thelhmutant is deficient in phytochromeB(Kendrick and Nagatani,The Plant Journal1:133–139, 1991), these results indicate that although phytochromeBclearly has an important role in the induction of the shade avoidance syndrome, it is unlikely to be the sole responsib

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02209.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—Four genotypes of tomato (Lycopersicon esculentumMill.) in the genetic background ‘Aha Craig’ were used: anaurea (au) mutant, deficient in the bulk light‐labile phytochrome pool; a high pigment (hp) mutant, showing exaggerated phytochrome responses at the time of de‐etiolation; theau,hpdouble mutant and the isogenic wild type (WT). A dramatic increase in plant height resulting from an increase in the length of all internodes for each of the genotypes studied was observed upon reduction of the red light: far‐red light photon ratio (R:FR) from 6.90 to 0.13 by addition of FR for the whole photoperiod. A concomitant increase in leaf length was also observed. Sinceauandau,hpmutants, deficient in the bulk light‐labile phytochrome pool, respond to this reduction in the R:FR these data demonstrate that the phytochrome pool that mediates this response is present and fully functional. Anthocyanin was detectable in the comparably developed young growing leaves of the WT andhpmutant under the high R:FR, but not in theauandau,hpmutants, suggesting that the potential for anthocyanin synthesis is correlated with the presence of the bulk light‐labile phytochrome pool. The kinetics of anthocyanin decrease in the young growing leaves were investigated in thehpmutant and the results suggest a very rapid cessation of flavonoid biosynthesis upon reduction of the R:FR. The functions of different phytochrome type

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02210.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The photocontrol of hypocotyl elongation has been studied in etiolated and light‐grown wild type (WT)Arabidopsis thaliana(L. Heynh) seedlings, and in two homozygous isogenic lines that have been transformed with the oatphy Agene coding sequence under the control of the cauliflower mosaic virus (CaMV) 35S promoter. For etiolated seedlings the inhibition of hypocotyl elongation by continuous broad band far‐red light (FR) is saturated at much lower photon fluence rates in the transgenic seedlings compared with WT seedlings. Furthermore, whereas de‐etiolation of WT seedlings leads to loss of responsiveness of the hypocotyls to prolonged FR, de‐etiolated transgenic seedlings continue to show a pronounced FR‐mediated inhibition of elongation. This may reflect the persistence of a FR‐high irradiance response (HIR) mediated by the introduced oat phytochromeA. Although the hypocotyls of light‐grown transgenic seedlings display a qualitatively normal end‐of‐day FR growth promotion, such seedlings display an aberrant shade‐avoidance response to reduced red:far‐red ratio (R:FR). These results are discussed in relation to the proposal that the constitutive expression of phytochromeAleads to the persistence of photoresponse modes normally restric

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02211.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—In most cultivars of lettuce (Lactuca salivaL,), red light acting through the red/far‐red reversible phytochrome system promotes full germination within the20–30°C range, but at progressively higher temperatures germination declines sharply. The relationship between this upper ternperature limit for germination and the temperature dependence of phytochrome action was investigated in Grand Rapids lettuce. In fresh seeds the GT50(temperature giving half maximal germination) wasca29–30°C. In these seeds, escape from far‐red reversibility did not occur at 35°C, a temperature above the GT50, but occurred rapidly at 27°C, a temperature below the upper limit. Increasing periods of dark pretreatment at high temperature (35°C) or increasing concentrations of the germination inhibitor coumarin caused a progressive decline in the GT50, Escape from photoreversibility did not occur at 27°C in seeds in which the GT50had been reduced to less than 25°C by coumarin or by prolonged high temperature pretreatment. These results indicate that there is a close correlation between the position of the upper temperature limit for germination, and the temperature dependence of phytochrome action. We conclude that factors that alter the upper temperature limit for germination do so by changing the temperature dependence of ph

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02212.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract—The long light irradiation requirement inPaulownia tomentosa(empress tree) seeds can be substituted by organic nitrates such as nitroglycerine, isosorbide di‐ and mononitrate, and pentaerythri‐tyl tetranitrate and a pulse of red light (5 min). The most effective was nitroglycerine (0.1 mM). Its effect depended on the time of application,i.e. a simultaneous presence of Pfrand these compounds was required. The effect decreased with delayed time of application after red light pulse. In seeds imbibed in nitroglycerine, an escape from far‐red light reversible action was similar to that obtained for seeds which can be induced to germinate by a brief exposure to red light. However, the application of nitroglycerine to seeds after a far‐red light pulse was ineffective. The effectiveness of organic nitrates also depended on the number of nitro groups in the compound. Isosorbide mononitrate was less effective than isosorbide dinitrate. Substances with structures similar to nitroglycerine, such as glycerol and glyceryl triacetate, in combination with the pulse of red light, failed to reduce the long light re

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1992.tb02213.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY