Spring Mobilization of Storage Nitrogen in Isolated Shoot Section of Apple

Abstract

The process of mobilization of nitrogenous compounds in trees during spring development was studied in short isolated shoot sections (usually bearing one bud each) of Golden Delicious apple trees. During leafing‐out of the bud, changes in the amounts of total, protein and soluble nitrogen and of soluble amino acids and amides in bark and wood were followed. The nitrogen required by the growing parts came mainly from protein breakdown in the tissues below the bud; in the tissues above the bud, total nitrogen decreased little, whereas the drop in protein nitrogen was considerable. In de‐budded sections and in internode sections where total nitrogen remained almost unchanged, protein hydrolysis occurred as well. It is concluded that the protein breakdown is not strongly dependent on the demand of the bud for nitrogen. Inversion of the sections did not result in any change in the pattern of nitrogen mobilization: a marked drop occurred in the nitrogen content of the physiologically basal part of the section and only a slight decrease in the apical part. The translocation of stored nitrogenous compounds to the growing parts seems to occur in the phloem, at least over short distances. Asparagine and arginine were found to be the major components of the soluble amino‐nitrogen fraction throughout. The relative importance of asparagine was reduced in tissue where a substantial loss of nitrogen occurred during leafing‐out of the bud. This is explained in terms of a preferential export of asparagine to the bud.

Qualitative and quantitative changes in nitrogenous compounds in senescing leaf and bark tissues of the apple

“…This may indicate that the storage nitrogen of apple bark tissue consists mainly of proteins, while the ethanol-soluble nitrogen is of secondary importance. O'Kennedy and Titus (1979), and Tromp andOvaa (1971, 1973) demonstrated that proteins contribute the greater part of the storage nitrogen exported to the growing parts.…”

“…1975a, Titus 1976. The nitrogen thus conserved is reutilized early in the spring for the development of flower buds and leaves (Tromp and Ovaa 1971, 1973, O'Kennedy and Titus 1979.…”

“…It has been recently recognized that instead of ethanolsoluble nitrogen, proteins play a major role as storage forms of nitrogen in apple shoot bark. Tromp andOvaa (1971, 1973) and O'Kennedy and Titus (1979) presented evidence that proteins contributed the greater portion of Abbreviations: ME, P-mercaptoethanol; Tris-, tris-(hydroxy-methyO-aminomethane; PVP, polyvinylpyrrolidone; EDTA, ethylenediaminetetraacetic acid; DEAE-cellulose, diethylaminoethyl-cellulose; R,,,, relative mobility; RuBP, ribulose-1,5-bisphosphate. Plan!…”

Soil and foliar nitrogen supply affects the composition of nitrogen and carbohydrates in young almond trees

“…Based on those studies, free amino acids would appear to be the primary source of nitrogenous reserves. However, more evidence suggests that protein may be the main form of N storage in the dormant tissues of apple and poplar trees (Tromp, 1970;Tromp and Ovaa, 1971;Shim et al, 1973;O'Kennedy et al, 1975;Kang and Titus, 1980;Titus and Kang, 1982;Kang et al, 1982;Coleman et al, 1991). Nevertheless, no tests had yet been reported on identifying the main form of storage N (protein v free amino acid) in young almond trees.…”

Influence of Rates and Frequency of Nitrogen Application the Year Previous on Spring Color in Kentucky Bluegrass

“…Although the effects of fall applications of nitrogen have been demonstrated with Kentucky bluegrass (Poa pratensis L.) by Wilkinson and Duff (1972) and with Agrostis and Festuca species by Powell et al (1967) (Tromp and Ovaa 1971;Cooper et al 1972), and lilac (Meyer and Splittstoesser 1969). Work on this phase is beins initiated.…”