The Balance Sheet of Metabolites For Potato Discs Showing the Effect of Salts and Dissolved Oxygen on Metabolism At 23° C1

Abstract

IntroductionThis paper presents a summarv of the effects of various salt and oxi-gen treatments so chosen that they comprise a range of conditions of peculiar interest to the student of salt accumulation.In any account of plant metabolism important processes may evade recognition unless a balance sheet of the principal metabolites can be prepared. Such balance sheets have rarely been attempted although the work of RAISTRICK et al. (31) on fungi is a notable exception. The work of RAISTRICK was concerned, however, with the use of organisms under standardized nutritional conditions to effect organic synthesis and transformations; it did not describe the effect on the metabolism of a given organism of a range of external and nutritional conditions. There is nieed of more attention to balance sheets of plant metabolism and especially so with reference to the vexed problems of respiration. Deviations from the familiar equations C6H1206 + 602 = 6CO2 + 6H20 + 674,000 cal. and C6H1206 = 2C2H50H + 2CO2 + 25,000 cal. often tacitly accepted as representative of plant respiration, are multiplying. The work of GANE and others (11,16,17) has demonstrated the production of volatile substances other than carbon dioxide and large discrepancies between respiration and the simple equations above may be encountered. For example, ARCHBOLD and BARTER (1) observed that the loss of sugar and acid in respiring apples exceeded by 17 to 30 per cent. the carbon dioxide evolved. On the other hand, DASTUR and DESAI (10) founid that in the respiration of rice the carbon dioxide evolved exceeded the utilization of sugar and they believe that acids formed durino the synthesis of protein form the source of the carbon involved. Again Luidegardh (23) states that in excised wheat roots 30 to 60 per cent. more glucose disappears than is accounted for by respiration and he tacitly assumes that the discrepalne is a measure of the sugar used in growth. In experiments with excised roots HOAGLAND has observed cases in which a very rapid disappearance of sugar occurred anid carbon dioxide productioni conitinued after the cells seemed to be free of sugar.2 1 This is the second of a series of papers on The Biochemistry of Salt Absorption by Plants. The authors are inidebted to PROF. HOAGLAND for proof-reading this paper.2 Results privately comlmunicated. PLANT PHYSIOLOGY From our present standpoint the outstanding fault in the above equations is lack of any implication that respiration concerns substances other than carbohydrates or that aerobic respiration and nitrogen metabolism are mutually dependent processes in plants.The variation between replicate samples of standard potato discs is small (47) and the effect of metabolism on the constituents of the tissue can be obtained by difference between the composition of the initial and final, experimentally treated, batches of discs. It is possible, therefore, to draw up a balance sheet with reference to any metabolite, e.g., carbohydrate, the fate of which is known with sufficient certainty so that its pr...

Respiration and Salt Absorption by Excised Barley Roots.

“…Calcium ion was found to exert a depressing effect upon these same activities. The extent of these phenomena are clearly seen in the data of Steward et al (24).…”

The Action of Inhibitors on Water Uptake by Potato Tissue

“…However, it seems not improbable that there is a metabolically' controlled system which accumulates water in a manner analogous to the way ions are accumulated. Indeed, suggestions of this sort, under the name of "active" water uptake, have been made by several authors (8,4; cf. also (3) It may be suggested that those metabolic processes which are intimately linked with growth are the same as those linked with aerobic water uptake.…”

“…Accordingly, we have mounted the potato discs so as to break the surface of a shallow unaerated solution. The apparatus consists of a fine net stretched over a large glass ring, 8 after six days has varied from 7 to 13%. Discs submerged in-the same volume of water, under a depth of about 5 mm., show less than half the water absorption.…”

The Onset of Tricarboxylic Acid Cycle Activity with Aging in Potato Slices

“…Studies of translocation in higher plants derived from sugar analyses of sap (10,26,27,28), aphid stylet exudates (24,28) and by the displacement of C14 from mature leaves (1,6,7,11,12,20,23), have produced the generally accepted view that sucrose is the main form of transported carbon in phloem tissue (19). These studies however have been confined to a very limited number of plant species.…”