Post-climacteric Stage Research Articles

The Control Properties of Phosphofructokinase in Relation to the Respiratory Climacteric in Banana Fruit

Glucose 6-phosphate, fructose 6-phosphate, fructose 1, 6-diphosphate, and triose phosphates, and the enzymes phosphofructokinase, aldolase, and glucose 6-phosphate dehydrogenase were extracted from banana fruit (Musa cavendishii, Lambert var. Valery) at the (a) preclimacteric, (b) climacteric rise, (c) climacteric peak, and (d) postclimacteric stages of ripening. The level of fructose 1, 6-diphosphate increased 20-fold whereas the concentration of other intermediates changed no more than 2.5-fold between stages a and c. For these same extracts, phosphofructokinase activity increased 2.5-fold whereas the activity of glucose 6-phosphate dehydrogenase and aldolase changed only fractionally. Substrate saturation studies (fructose 6-phosphate) of phosphofructokinase activity showed a decrease in the [S](0.5) from 5.6 to 1.7 mM betwen stages a and c. The enzyme from both sources seems to be regulated by a negative cooperative effect with the control being more stringent in the enzyme from stage a. The difference in enzyme activity is consistent with the increase in respiratory activity between the two stages.

Effect of 2-Chloroethyl-Trimethylammonium Chloride on Climacteric Changes in Apples

The effect of CCC on the release of ethylene in apple varieties Jonathan, Sudetská reneta , and Panenské české was followed. CCC applied on fruits in the form of paste during the vegetation period induced the time shift of climacterium (Fig. 1 and 2). Low concentrations of CCC (0.1 per cent) forced the maturation by 10 days and concentrations higher than 1.0 per cent of CCC prolonged the climacterium by as much as 1 month. On the other hnad, CCC applied in the form of aqueous solution did not influence expressively changes in the ethylene release during the preclimacteric and climacteric stages. In the postclimacteric stage lower concentrations of CCC (about 0.25 per cent) stimulated the ethylene formation which reached the level of ethylene production observed in unseeped apples (Fig. 3).

Aspects of lipid metabolism in higher plants—II. The identification and quantitative analysis of lipids from the pulp of pre- and post-climacteric apples

The identity, composition and concentration of each individual lipid in the pulp of apples has been determined for fruit in both the pre- and post-climacteric stages of ripening. The fatty acid composition of each acyl lipid is similar for apples at both stages of ripening. Although linoleic acid was the main fatty acid component of most of the major acyllipids, linolenic acid was the predominant acid in mono- and di-galactosyl diglycerides. Glucocerebrosides contained only hydroxylated fatty acids. The decrease in the level of linolenic acid in the total lipid at the post-climacteric stage was mainly due to a decreased concentration at this stage of galactosyl diglycerides. The concentration of phosphatidyl glycerol was also lower in the post-climacteric fruit. Most other lipids showed no marked differences in concentration between the two stages. The results, which suggests a selective degradation of plastid membranes during ripening, are discussed in relation to current theories of fruit ripening.

Biochemical Studies on Post‐Ripening of Banana

Some fundamental studies were undertaken in order to get some insight into the process of post-ripening of banana by studying the changes in carbohydrate metabolism and the changes in respiratory mechanism during the course of banana ripening. 1.During the course of banana ripening, it is concluded that sucrose is synthesized first directly from starch and subsequently hydrolyzed into glucose and fructose in the post-climacteric stage. In this process phosphorylase appears to be the main enzyme involved in the breakdown of starch. 2.During the course of post-ripening, water content of the flesh increases gradually. Soluble pectin increases four times in the climacteric stage, and then decreases. Tannin content remains unchanged. 3.No peroxidase activity is detected through each stage of ripening, but considerable intensity of catalase activity is detected. The catalase activity in pre-climacteric banana is stronger than that in the climacteric. 4.The entire terminal oxidase of preclimacteric banana flesh is cyanide-resistant, but as the climacteric stage reaches, one-fifth of it becomes cyanide-sensitive. Malonate poisoning appeares to occur to a very little extent. 5.Citrate acts as a substrate toward the respiratory system of preclimacteric tissue, but as an inhibitor toward that of ripe banana. An interpretation is made on these effects of citrate. 6.With the aid of the uncoupling agent, 2,4-dinitrophenol, it is shown that the respiratory rate of the preclimacteric but not of the climacteric banana flesh is limited by the capacity of the phosphate transfer system. ATP-ase develops during the course of ripening and appeares to be a factor which put forth the respiratory increase in the climacteric stage. This behavior is belived to be the general feature of the catabolism of reserve substances like starch.

The Organic Acid Metabolism of Bramley's Seedling Apple Peel1

SUMMARY 1. The effect of various Krebs cycle acids on the respiration of disks of apple peel at various stages of maturity was measured in a Warburg respirometer. 2. Peel tissue from apples at the pre-climacteric and early post-climacteric stages apparently contain sufficient of the Krebs cycle acids used, with the excep tion of succinate, to maintain oxidative processes at a maximum. 3. The addition of malate causes a large increase in the C02-output of peel from post-climacteric and senescent fruit but not from pre-climacteric fruit, and a close correlation exists between the climacteric and this decarboxylation of malate. The decarboxylation of malate does not affect the rate of 02-uptake of peel tissue. The possible part played by the decarboxylation of malate in the increased C02 output at the climacteric is discussed. 4. Added pyruvate is decarboxylated by the tissue at all stages of storage life. 5. The decarboxylation of added malate is an aerobic fermentation, resulting in the quantitative production of acetaldehyde. Although the presence of oxygen is necessary, the rate of 02-uptake is not affected by the reaction. Pyruvate decar boxylation does not require the presence of oxygen. 6. The 02-uptake of peel from senescent apples can be stimulated by addition of malate, succinate, and a-ketoglutarate. No evidence was obtained, however, of oxidation of fumarate, citrate, or pyruvate. The addition of malate to senescent tissue restores the lower endogenous rate of 02-uptake to that of early post climacteric tissue.