¹⁴C‐Studies on Apple Trees. VIII. The Seasonal Variation and Nature of Reserves

Abstract

The nature, seasonal variation and mobilization of reserves in Malus × domestica have been studied by means of 14C, carbohydrate analyses and extractions of xylem sap. Following exposure to 14CO2 in the autumn, the majority of the 14C absorbed is found in the root. During the winter and in particular the spring the amounts of 14C in the top and root are reduced to approximately 40 per cent of the autumn values; in the root the amount of dry matter was also considerably reduced. In the tops, most of the 14C absorbed was found as methanol (80 %)‐soluble 14C which also showed the greatest seasonal reduction; sorbitol, sucrose or glucose in particular are responsible for the decrease in concentration within this fraction. Maximum values for methanol‐insoluble 14C were found in March. In the root, the highest values for absolute changes were found for methanolinsoluble 14C. Hydrolysis of this fraction showed considerable activity in glucose. In the root there was also considerable activity in a precipitated fraction of the methanol extract. Eluates of xylem sap from apple branches contained primarily sorbitol, the highest concentration of which was found at the beginning of March. For a tree with a dry matter weight of about 300 g, the utilization of reserves from the tree in the spring was calculated to be at least 13 g of dry matter. However, only a minor part (less than 25 per cent) of the latter appears to serve as building material for new growth.

Changes in non‐structural carbohydrate concentration in 1‐year‐old shoots of ‘Braeburn’ apple(Malus domestica)over two consecutive years

“…It is thought that the long photosynthetic period after harvest could be responsible for the very high yields of New Zealand apple trees compared to the Northern Hemisphere (Tustin et al 1997). Because previous studies into carbohydrate partitioning have been carried out in the Northern Hemisphere (Murneek 1933;Priestley 1960Priestley , 1962Hansen & Grauslund 1973;Kandiah 1979b), these experiments were repeated using apple trees grown in New Zealand conditions in which the carbohydrate profile might be expected to be quite different as a result of the long period of leaf retention after harvest.…”

“…Although seasonal carbohydrate partitioning has been studied in fruit trees in detail (Murneek 1933;Priestley 1960Priestley , 1962Hansen & Grauslund 1973;Kandiah 1979b), most studies have not measured the full range of non-structural carbohydrates found in apple trees (starch, sorbitol, sucrose, glucose, fructose). Sorbitol is a major phloem-transported carbohydrate and component of the non-structural carbohydrates present in apple trees, first identified in 1968 (Bieleski 1969(Bieleski , 1982.…”

Dynamism in Reserve Carbohydrates until the Following Growth Season in Japanese Apricot ^|^lsquo;Nanko^|^rsquo; Tree

“…Studies of the dynamism of reserve carbohydrates using radioisotopes or stable isotopes have been performed in deciduous trees, such as pear (Teng et al, 1999), fig (Matsuura et al, 2001), grape (Okamoto, 1979), apple (Hansen and Grauslund, 1973;Kandiah, 1979;Quinlan, 1969), and pecan (Lockwood and Sparks, 1978a, b). In these species, fruit begins to grow after or simultaneously with shoot expansion.…”

“…For woody perennial crops, reserve carbohydrates are required for dormancy and subsequent spring bud break (Hansen and Grauslund, 1973;Tromp, 1983;Worley, 1979), and the Aug.-and Sep.-defoliated sweet cherry tree had small, yellow leaves and poor fruit set the following year (McCamant, 1988). Hence, it is important to clarify the characteristics of the distribution of reserve carbohydrates to maintain abundant yield and sound growth of the tree.…”

Mobilization of carbon reserves in young walnut trees

“…The few authors who addressed this point generally concluded that reserves are mainly used as respiratory substrates in broadleaved trees ; a low proportion, less than 20 or 25 %, ©Societe botanique de France 1993. /SSN (en cours). is incorporated in new tissues (Hansen, 1967 ;Hansen and Grauslund, 1973 ;Kandiah, 1979).…”