The phloridzin content of dormant terminal twigs of Malus rootstock clones was not related to the vigor imparted to the scions. In young seedling trees it varied with the nutritional status of the plant; an acute deficiency of nitrogen, sulphur, or calcium resulted in a significant increase in phloridzin accumulation. Phloridzin is synthesized readily in the leaf from C14O2 in the light and appears to be stable once formed. Phenylalanine-C14 and tyrosine-C14, when fed to leaf disks, are incorporated into the C6–C3 moiety of phloridzin which includes ring B. Tyrosine is not as effective as phenylalanine. Acetate-C14 is incorporated into ring A. Phloroglucinol is not involved in the synthesis of phloridzin. A method for the quantitative determination of phloridzin is described, also a semimicro method for its alkaline hydrolysis. The large amounts of radioactive D-glucitol formed from a wide variety of precursor compounds indicate a central role for it in the carbohydrate metabolism of Malus.
The daily variation of sorbitol, starch, sucrose, glucose, and fructose were estimated in the leaf of the apple, Malus pumila Mill., at 2-h intervals over 24-h periods in each of the months June to October, inclusive, 1968. Marked daily fluctuation in sorbitol concentration was observed in all months, accompanied by more moderate variations in the other carbohydrates. The patterns of concentration variability in sorbitol and starch were relatively similar compared to the more irregular patterns of the three sugars, sucrose, glucose, and fructose. In conjunction with its invariably very high leaf concentration relative to the other carbohydrates, the general daily pattern of sorbitol content, namely, a marked nocturnal decrease followed by a great increase during daylight, indicated that sorbitol is the major photosynthetically derived carbohydrate and is further evidence that sorbitol is a reserve carbohydrate in apple leaves.
Callus cultures from 1-year-old twigs of the apple, Malus pumila, cultivars McIntosh, Cortland, and Red Delicious, and of the crabapple rootstock, Malus robusta No. 5, were successfully isolated and maintained on a medium with sorbitol as the sole carbon source. Investigation with various carbon sources, each at 3% concentration, showed that McIntosh callus grew equally well on sorbitol, sucrose, and glucose. Cortland and Robusta cultures responded equally to sorbitol and glucose but poorly to sucrose. The relative growths of the callus cultures on sorbitol were in the decreasing order, McIntosh, Cortland, and Robusta. Sorbitol served as an excellent carbon source for all three cultures.
Initiation of stem callus cultures on a nutrient medium with either 3% sucrose and (or) 3% sorbitol as carbon source was attempted with 17 species selected from the following genera of the Rosaceae: Amelanchier, two spp.; Crataegus, one sp.; Malus, one sp.; Prunus, nine spp.; Pyrus, one sp.; Sorbus, two spp.; and Spiraea, one sp. In the case of Malus pumila var. niedzwetzkyana (crabapple), sucrose and sorbitol media were equally effective in callus initiation, and equal growth was maintained on these media. Callus of Spiraea vanhouttei was initiated only on sucrose medium and no callus of Prunus tenella formed on either medium. With all other species, callus was initiated and (or) gave better growth on further subculture on sucrose than on sorbitol medium, except for Prunus persica (peach), which grew better on sorbitol.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.