Rapid Phytochrome-mediated Changes in Adenosine 5'-Triphosphate Content of Etiolated Bean Buds

The effect of red and far-red light on proton secretion from mesophyll-cell protoplasts of Vicia faba L

The influence of red and far-red irradiation on the transport of H(+) and (86)Rb(+) through the plasmalemma was studied using parenchymal protoplasts isolated from Vicia faba leaves. The results indicate that red light stimulates H(+) secretion and the uptake of (86)Rb(+). Moreover, it has been demonstrated that far-red irradiation acts antagonistically with respect to red light in both these processes.

Pyridine nucleotides and redox-charge evolution during the induction of flowering in spinach leaves

In the long-day plant Spinacia oleracea changes in the pool size of pyridine nucleotides have been followed under different photoperiodic conditions. In short days (vegetative state), the dark and light phases of the cycle are characterized by specific reciprocal changes in NAD and NADP pool sizes. As a consequence, the ratios of NADH/NAD+NADH and NADPH/NADP+NADPH, which are respectively considered to represent the catabolic and anabolic state of metabolism, also show a characteristic pattern. Upon transfer to continuous light, i.e. during floral induction, a decrease in anabolic metabolism is paralleled by an increase in catabolic metabolism. In the floral state, both the catabolic and the anabolic couples of the pyridine nucleotides are considerably depressed, possibly reflecting the enhanced senescence of induced leaves. The results are discussed in relation to the involvment of the nucleotides in stoichiometric coupling of metabolic compartments at the cellular level in response to environmental signals.

Adenine nucleotides and energy charge evolution during the induction of flowering in spinach leaves

Changes in adenine nucleotides pool size levels have been investigated in spinach leaves (Spinacia oleracea. L. cv. Nobel) in order to characterize the transition from the vegetative to the reproductive development. The transient changes reported in this study are the earliest responses observed to date in leaves during photoperiodic induction. These results are discussed in relation to Prigogine's theory of systems far from equilibrium.

Control of mitochondrial activities by phytochrome during greening

Mitochondria isolated from 7-day old darkgrown Avena sativa L. (var. Arnold) laminae given 5 min illumination of red light, followed by varying lengths of darkness up to 3 h, showed at least a twofold increase in the rates of both NADH-dependent oxygen consumption and respiratory chain phosphorylation over those of mitochondria isolated from unilluminated tissue. Similar organelles, isolated from tissue given either far-red or red followed by far-red pretreatment, exhibited rates of both functions of between 25% and 75% below those of the mitochondria from unilluminated tissue. The induction-reversion criteria for phytochrome control of respiration and oxidative phosphorylation were satisfied under all experimental conditions during the greening process.Treatment with continuous far-red light, acting presumably through the 'high irradiance' reaction of phytochrome, served to disengage phytochrome activity from photosynthesis. The stimulation of oxidative phosphorylation still occurred under these conditions, slightly slower but much more prolonged in the absence of ATP from photophosphorylation.

Phytochrome Control of Cell Wall-bound Hydroxyproline Content in Etiolated Pea Epicotyls

The red light inhibition of growth of the intact pea (Pisum sativum L. cv. Alaska) third internode was correlated with an increase in the content of cell wall-bound hydroxyproline. These changes were detected 3 hours after irradiation, and possibly at 1 hour. Far red light reversed the effects of red light. The iron chelator alpha,alpha'-dipyridyl reversed the red light effects on both growth and hydroxyproline content. Using segments incubated in vitro, no phytochrome-mediated change in hydroxyproline content could be observed, perhaps because of an overwhelming wounding response. If plants were irradiated in situ and grown for 8 hours before excision and incubation of segments, some enhancement of hydroxylation by red light was detectable both colorimetrically and radioisotopically. The red light inhibition of segment growth was reversed by alpha,alpha'-dipyridyl. These results are examined in reference to the role of extensin in normal and induced growth cessation.

Partial purification and some properties of a cholinesterase from bush bean (Phaseolus vulgaris L.) roots

A cholinesterase was partially purified from bush bean (Phaseolus vulgaris L.) roots by using acridinium-based ligand affinity chromatography. The procedure gave a 78-fold increase in specific activity, although at least three inactive contaminants remained. The enzyme activity was maximal against acetyl esters of choline and was inhibited by neostigmine. Di-isopropyl phosphorofluoridate completely inhibited activity at concentrations greater than 0.1 mM. The catalytic centre activity was 2 X 10(-4) times that of electric eel acetylcholinesterase. Cholinesterase activity appeared as a peak (s = 4.2 +/- 0.1 S) after isokinetic sedimentation. The Stokes radius was 4.00 nm and the apparent molecular weight was 72700 +/- 1900. The smallest active and native form of the enzyme appeared to be a monomer. This contrasts with animal acetylcholinesterases, in which the smallest active and native forms are multimeric.

Irradiation-enhanced Phytochrome Pelletability: Requirement for Phosphorylative Energy in Vivo

Short, high intensity pulses of red and far red light are used to study, at room temperature, the kinetics of the in vivo dark reaction responsible for irradiation-enhanced phytochrome pelletability. The t((1/2)) for this reaction is 2 seconds at 25 C in both Avena shoots and Zea mays coleoptiles. This is the most rapid phytochrome-far red-absorbing form (Pfr)-mediated cellular response thus far reported. Anoxia, KCN, NaN(3) and carbonyl cyanide p-trifluoromethoxyphenylhydrazone reduce the rate (but not the final extent) of the reaction by more than an order of magnitude. The rate of the reaction under these conditions is strongly correlated with the inhibitor-induced reductions in cellular ATP levels. Likewise, recovery in ATP levels upon withdrawal of the inhibitors is accompanied by a parallel recovery in the rate of the reaction. Cytochalasin B blocks cytoplasmic streaming without diminishing the pelletability response. Colchicine is likewise without effect. These data suggest a requirement for phosphorylative energy in one or more of the Pfr-dependent intracellular events leading to enhanced phytochrome pelletability. The possibility that this event might represent an ATP-dependent modification of the pigment protein itself in the Pfr form is discussed.

Phytochrome-controlled Hydrogen Ion Excretion by Avena Coleoptiles

A red light-induced, far red reversible stimulation of proton efflux from apical segments of etiolated Avena sativa L. cv. Victory coleoptiles was observed. The acidification responses to red light and also to auxin were not the consequence of respired CO(2). The response to red light was strongly inhibited by cycloheximide and carbonyl cyanide, m-chlorophenyl hydrazone, but mannitol had a stimulatory effect. Red light and auxin applied together yielded a greater than additive response, in comparison to the effects of the two stimuli applied separately.

Lack of influence of phytochrome on membrane permeability to tritiated water

The water permeability of tissues was investigated by measuring the efflux of (3)HHO from previously loaded (in darkness) etiolated bean buds (Phaseolus vulgaris L. var. Red Kidney), pea epicotyl segments (Pisum sativum L. var. Alaska), and oat coleoptile segments (Avena sativa L. var. Garry). Red light, far red light, or darkness was applied at the time of transfer of tissue from labeled to unlabeled medium. There were no effects of light on half-time for efflux or on the maximum level of radioactivity in the medium. Based on these criteria, phytochrome exerts no apparent control over water permeability.

Endogenous oscillations in pathways of energy transduction as related to circadian rhythmicity and photoperiodic control

Evidence is presented for endogenous rhythmicity in energy transducing sequences of cellular metabolism which result in a circadian rhythm in adenylate "energy charge" and redox state (NADPH/NADP). From phase dependent photocontrol of enzymatic activity and pyridine nucleotide pool-size levels it is concluded that light - via photoreceptor(s) of photoperiodic control - modulates energy flow under conditions where overall energy transduction displays a circadian rhythm. The results are discussed in relation to temporal organization of development in general.