Bisulfite compounds as metabolic inhibitors: nonspecific effects on membranes

Bisulfite compounds are shown to be nonspecific inhibitors ofphotosynthetic processes and of ion transport in green tissues.CO₂ fixation and light-dependent transient changes in externalpH are inhibited about 50% by 5x10^–4 M glyoxal-Na-bisulfite.Chloride uptake in the light and in the dark is inhibited tothe same extent at this concentration. At 5x10^–3 M theinhibitor reduces ATP levels in the light and in the dark, andeffects on glycolate oxidase and PEP carboxylase are observed.The extent of inhibition is dependent on time of treatment withglyoxal-Na-bisulfite and freshly prepared NaHSO₃ is equallyas effective as the addition compound. Possible explanations of the bisulfite effects and the relationshipsto SO₂ effects on photosynthesis are discussed. (Received September 1, 1971; )     

Growth Responses of Dwarf Bean to Infection by Pseudomonas phaseolicola (Burk) Dows

At an early growth stage inoculation of both unifoliates ofdwarf beans with Pseudomonas phaseolicola (Burk) Dows. Race1 inhibited trifoliate production, but inoculation of one unifoliateonly reduced subsequent leaf expansion, and the opposite uninfectedunifoliate became significantly larger than unifoliates on uninfectedplants. Inoculation of the first or second trifoliates or thecotyledonary node at a later developmental stage all reducedprimary-shoot growth by 25 to 30 per cent, but there were markeddifferences in the extent of secondary-shoot development inleaf axils below the inoculation point. The growth effects were related to the distribution and activityof the bacterial toxin within the plant, particularly to differencesin the rate of invasion of apical regions. The primary toxineffects appear to be on apical function and leaf expansion.     

Electron Microprobe Analysis of Silicon and Other Elements in Developing Silica Cells of the Leaf and Internode of Cyperus alternifolius

This study is an analysis of changes in accumulation of Ca,K, Mg, Mn, Fe, P, and Na involved during the development ofsilica cells in the leaf and internode of Cyperus alternifolius.Electron microprobe analysis shows that with the accumulationof silicon in the silica cells, there appears to be a decreasein the accumulation of potassium and phosphorus; in contrast,the accumulation of calcium and iron is increased. Manganeseand magnesium were found in non-detectable quantities in thesedeveloping epidermal and silica cells. The effect of silicondeposition on the accumulation of these elements is discussed.     

Limitations to the Accumulation of Starch in the Developing Wheat Grain

The postulate that photosynthetic capacity limits the rate ofaccumulation of starch and dry matter in the developing wheatgrain has been tested by defoliating plants growing in the field,and by culturing detached ears on solutions of sucrose. In mostcases complete defoliation did not reduce the amounts of starchor dry matter produced 4 to 10 days later, or affect the amountsof sucrose in the grain. Increasing the potential supply ofsucrose above normal levels by culturing did not lead to increasesin either the deposition of starch or the quantity of sucrosein the grain. Removing leaves caused small depressions in thegain in fresh weight of the grain, and where defoliation didreduce the accumulation of starch there was no comparable effecton the amount of sucrose in the grain. Accordingly, it is concludedthat the postulate stated above is invalid. The case in support of the concept that it is the mechanismregulating the passage of sucrose into the grain which imposesa limitation on the accumulation of starch is presented.     

Solute Accumulation in Plant Cells V. An Aspect of Nutrition and Development

The need to re-evaluate concepts of salt and solute accumulationin the light of evidence derived from cells at all stages oftheir growth and development is recognized. The problem is seenin terms of the nutrition of flowering plants, the growing cellsof which are essentially heterotrophic, and the solutes of whichare progressively acquired and redistributed during ontogeny.This is traced from the zygote in the embryo sac to an establishedplant body with its evident ‘source-sink’ relationshipsand physiological ‘division of labour’ between organs.The evidence accrued from aseptic cultures which were manipulatedto reveal the range of solutes in cells which simulated thenormal course of development in situ as they multiplied, vacuolated,enlarged, and eventually matured. The regulatory control exercisedby cells in these developmental stages over the total osmoticvalue and the relative composition of their solutes (organicand inorganic) is both described and interpreted. The reversiblechanges that may occur (within a regulated osmotic value) inthe solutes of established cells as they replace sugars by saltsof organic acids, by organic nitrogen compounds, or by alkalihalides are both described and related to events that occurin the developed plant body. Particular significance is attachedto the consequences of the normal need of land plants to acquirenitrogen from nitrate and of the intervention of reduced nitrogenunder circumstances in which the need for non-metabolizableions (e.g. alkali halides) is, thereby, drastically curtailed.Cells in multiplication require energy to create new structureand do not emphasize the accumulation of solutes in bulk; however,when they enlarge, energy is obligated to the storage of solutes(organic and inorganic) to support their cytoplasm which isbeing ‘spread out thin’. These events involve morethan the properties of membranes, or their relations to individualions or molecules, for they require an understanding of cellsas compartmented, metabolic, and osmotic machines, and of theirvariously obligated energy relationships. Moreover, the subjectnow needs to be seen as an aspect of the over-all nutritionof cells, organs, and organisms as they grow and develop.