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ATTENTION to phytochrome and phytochrome-controlled physiological responses has been devoted chiefly to the red and far-red regions of the visible spectrum. Radiation of shorter wavelengths, however, also has an influence on plant development through its action on phytochrome.('. ' ) The absorption spectra of the two forms of phytochrome show, in addition to the major absorption bands in the red and far-red regions, minor bands in the blue and near u.v.@$ which are also effective in the photoconversions of phytochrome, PR s PFR. The present paper presents quantitative data on the effectiveness of monochromatic light in the spectral region between 300 and 800 nm for the transformations of PR and PFR in purified solutions.The photochemical transformations of phytochrome are first order in both directions.(Z) The rate equations for the transformations of PR and PFR by monochromatic light of wavelength Xare:[PR] and [PFd are the mole fractions of PR and PFR at time I, [PR m] X and [PFR a] X are the mole fractions at the photostationary state ( t = a) in monochromatic light of wavelength A, [PRO], and [PFRo] are the mole fractions at time t = 0 and KA is the first-order rate constant. Eh is the intensity of monochromatic light (Einstein cm-2 sec-l), eRA and cFRA are the extino tion coefficients of PR and PFR at h (cm2mole-',to the base 10) and C$R and,C$FR are the quantum yields for the transformations of PR and PFR (moles Einstein-l). Equation (1) requires the absorption of radiation by the sample to be small so that the intensity of radiation at any point in the sample can be assumed to be equal to the incident intensity. The action, defined as the product €4, can be determined at any wavelength from the value of KAr provided EA and [PR m ]~ or [PFR a]/\ are known. Previous (2, 5, calculations of the €4 products were based on the assumption that the red actinic light converted essentially all of the PR to PFR. This was assumed because difference spectra showed that the same maximal degree of transformation was achieved by irradiation

Prolonged irradiation at moderately high intensities is a requirement for anthocyanin synthesis in many plants. Action spectra for anthocyanin formation, however, are different for nearly every species examined (1,5,6,7,9). In general, a maximum is present between 400 and 500 mg (blue) or one between 400 and 500 m, and another between 600 and 800 myi (blue & red). In some species a second controlling photoreaction which requires brief irradiances at relatively low intensities is present (1, 6). The latter exhibits all the characteristics of phytochrome (4) with a promotive action on anthocyanin production by the red region of the spectrum (600-700 me) that is reversed by far red (700-800 miL).A somewhat more responsive and experimentally convenient plant than the species previously used was desired to facilitate work on anthocyanin and examination of the photoreactions involved. Sorghum seedlings attracted attention because of marked reddening of the plants at an early stage of growth. Preliminary experiments showed that seedlings of many varieties of sorghum produced a great deal of anthocyanin. The availability of large lots of seeds of Wheatland milo (Sorghum vulgare Pers.) prompted its selection for further studies, some results of which are described herein. Materials & MethodsSeeds of Wheatland milo were germinated in darkness on 8-mesh stainless-steel screens immersed in aerated tap water. Temperatures of 25 to 26 C during germination and subsequent shoot growth produced seedlings of adequate size in 3Y2 to 4 days.The temperature during the treatments and during the post-treatment incubation period was maintained at 20 C. When intact seedlings were placed in petri dishes the root tended to lift the shoot away from the substrate. Excising the roots resulted in no measurable effect on the amount of anthocyanin produced in the internode so long as the seed remained attached to the shoot. Therefore, the standard procedure was to remove the roots prior to treatment. The intact shoots with seeds attached were placed on water-soaked filter paper in petri dishes or plastic boxes. These shoots were exposed to various light Received June 16, 1962. 25 regimes, then harvested immediately or after a period of incubation in complete darkness. When a darkincubation period was used, the seedlings were generally harvested 24 hours after the beginning of the light treatments. In this way the total time allowed for anthocyanin synthesis was kept constant irrespective of the duration of the light period. Experimental evidence indicated that with light periods up to 9 hours, dark-incubation periods of 24 hours produced only about 15 % more anthocyanin than was formed with dark-incubation periods of 15 hours. At the conclusion of the experiment the seed and the coleoptile were discarded and the first internode was cut into small segments. Usually, five first internodes were extracted in 5 milliliters of 1 % HCl methanol and held 24 hours at 5 C. Anthocyanin content was determined from absorbancy values (1 = 1 centimeter) at...

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Intact plant vacuoles were prepared in large numbers (106)from protoplasts of mature leaves, flower petals, stems, pedicels,filaments, styles, and young fruits. Treatment of protoplasts with 0.2 molar K2HP04-HCl, pH 8, with slow stirring resulted in gentle osmotic rupture of the protoplasts and release of intact vacuoles. Particulate components of the protoplast, less the vacuole, were largely shed as an aggregate, which was removed byfiltration. Vacuoles were recoveredfrom thefiltrate by low-speed centrifugation. The general procedure was also used to isolate chloroplasts with a high degree of integrity and excellent photochemical activity.

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even at its optimal concentration, was nearly as effeetive as the endogenous stimulator.Prolonged exposure of spores to stimulator solutions at appropriate temperatures, induced, in addition to increased germination, the formation of structures resembling appressoria, infection hyphae, infection pegs, and substomatal vesicles. Definitive evidence that these responses were brought about by the same substance that stimulates germination is not yet available. Dilution curves for germination and for vesicle formation are shown in figure 4. The curves exhibit a measure of similarity but also appear to differ appreciably.i\IECHANISM OF STIMULATION: Although the detailed mechanism is unknown, it is evident that the stimulator operates by overcoming the influence of an endogenous inhibitor. Thus, the self-inhibition exhibited by concentrated masses of spores on water or agar was abolished by addition of stimulator extract. Furthermore, the stimulator was shown to overcome the influence of endogenous inhibitor solution on inhibitor-depleted spores (table IV)

A bstract. Phototransformable protochlorophyllide holochrome was prepared from etiolated bean leaves. The detergent Triton X-100 in the presence of glycerol and tricine-KOH buffer (p14 8) enlhanced the extractability, specific activity, and phototransformability of the holochrome. Purification was achieved by polyethylene glycol-6000 precipitation and hydroxylapatite, DEAE-cellulose, and agarose chromatography.