Dye Reduction by Illuminated Chloroplast Fragments.

نویسندگان

  • A S Holt
  • R F Smith
  • C S French
چکیده

It has been demonstrated that when isolated chloroplasts are illuminated in the presence of aqueous solutions of certain oxidants, oxygen evolution occurs (2, 5, 6, 7, 8, 13). Provided stoichiometric relationships between the reactants and products prevail, the reaction rate can be measured in terms of oxygen production or in terms of changes in the concentration of whatever other molecular or ionic species are involved, e.g., changes in the concentration of the oxidant, of the reduction product, or of H+. Of these possibilities, oxygen production, measured by manometric or colorimetric methods, has been most commonly used. Measurements of decrease in the oxidant concentration or increase in the concentration of the corresponding reduction product appear to be limited to determinations with highly colored reagents, e.g., dyes. Hydrogen ion formation or disappearance, which allows the use of acid-base titrations, is limited to special cases, as for example, reduction of an oxidant such as ferricyanide (7). From the foregoing possible methods only two appear to be adaptable to rapid determinations of reaction rates when micro amounts of chloroplast material are to be used. These are: (a) colorimetric determination of oxygen as oxyhemoglobin by the method of HILL (5), and (b) determination of the decolorization of oxidation reduction indicators (8). Such micro methods require the elimination of secondary influences which can be neglected in manometric determinations. In the determination of oxygen as oxyhemoglobin it is necessary to remove oxygen by preliminary degassing of the reagents and chloroplast material. In the case of reduction of indophenol dyes, the presence of small quantities of natural reducing substances, such as ascorbic acid, introduces a thermal reduction which might invalidate the observations. In addition to thermal reductions not involving 02 production, photochemical reduction of certain dyes may occur, which likewise does not involve 02 production. Such reduction was found when methylene blue or thionine was added to the supernatant fraction from a brei made from

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Studies on photosynthetic processes. I. The effect of light intensity on triphosphopyridine nucleotide reduction, adenosine triphosphate formation, and carbon dioxide assimilation in spinach chloroplasts.

Although there is a considerable amount of information on the effect of light intensity on O2 evolution and, to a lesser extent, COz assimilation in intact plants (l), there are few reports on the effect of light intensity on the photosynthetic processes known to occur in the isolated chloroplast and chloroplast fragments. Isolated chloroplasts have the ability to assimilate CO2 (‘2, 3), and ch...

متن کامل

The oxidation of manganese by illuminated chloroplast preparations.

It has long been known that manganese is an essential micronutrient of plants. Although the precise functions of manganese are unknown there is evidence that it may be concerned in chlorophyll synthesis, photosynthesis, respiration and nitrate assimilation. Decreased photosynthesis under conditions of manganese deficiency was originally attributed to the diminished chlorophyll content, but more...

متن کامل

Oxidative photosynthetic phosphorylation by spinach chloroplasts.

In an earlier note, evidence was presented for the occurrence of a new type of chloroplast-catalyzed photosynthetic phosphorylation called “oxidative photophosphorylation” (I). When spinach chloroplasts are illuminated in the presence of orthophosphate, adenosine diphosphate, and a dye such as trichlorophenol indophenol, adenosine triphosphate is generated provided oxygen is available, but not ...

متن کامل

Carbon dioxide and the reduction of indophenol and ferricyanide by chloroplasts.

Pea chloroplasts isolated in salt media show decreased rates of 2:6 dichlorophenolindophenol (DCPIP) and ferricyanide reduction when depleted of CO(2) at pH values below 7.5. The greatest effect of CO(2) was on uncoupled systems. The incorporation of 10(-2), 2 x 10(-2) and 4 x 10(-2)m sodium acetate into the reaction mixtures progressively increased the bicarbonate concentration required for ha...

متن کامل

In vivo fragmentation of the large subunit of ribulose-1,5-bisphosphate carboxylase by reactive oxygen species in an intact leaf of cucumber under chilling-light conditions.

Previous studies have demonstrated that the large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase (Rubisco) is site-specifically cleaved by a hydroxyl radical (*OH) generated in the illuminated chloroplast lysates or by an artificial *OH-generating system. However, it is not known whether such cleavage of the LSU by reactive oxygen species (ROS) actually occurs in an intact leaf. When le...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Plant physiology

دوره 26 1  شماره 

صفحات  -

تاریخ انتشار 1951