Studies on alternate bearing and reserve nutrients of satsuma mandarin [Citrus unshiu], 2: Winter reserve carbohydrates and nitrogen compounds in 'Aoshima' mandarin trees under different nutrition conditions

1) 'Aoshima' satsuma mandarin trees (Citrus unshiu Marc. cv. 'Aoshima') on trifoliate orange were used. At the start of the experiment in 1985, the trees were seven years old. During two years, there were two levels of nitroge (N) nutrition conditions: (1) about two-fold standard fertiling at the tree ages and (2) non-fertilizing. Carbohydrate nutrition conditions were two levels: (1) all thinning and (2) non-thinning with shading at the first year. Yields, fruit qualities, flower volume and sprouting volume of the following year were surveyed. In early March, before germination in l986 and 1987, they were uprooted and sectioned into eight overground and six underground divisions. Nitrogen content and carbohydrate content of the divisions were determined by the methods of our former report in 1992. Carbohydrates were divided by 80% ethanol soluble sugar and starch fractions. 2. In both years, the nitrogen content in the leaves (old and spring leaves, summer and fall leaves) was the highest and followed by that in fine roots. In the first year, the difference between fertiling and non-fertiling was apparent in fine and medium roots, but the nitrogen content in old leaves and green twigs raised under the low carbohydrate condition. In the second year, the difference between fertilizing and non-fertilizing appeared in leaves and fine roots, as well as in medium branch bark, thick root bark and medium roots. 3. The sum of soluble sugar and starch in the thick root bark was the highest and followed by that in leaves in both years. In the underground divisions such as thick root bark, starch is the main constituent of carbohydrates. In both years, the difference between low and high carbohydrate conditions was apparent at the starch content in thick root bark. In the following year, the yield of the completely thinned trees became better than the others, and the starch content in thethick root bark decreased