An Analysis of Growth and of Form in Young Apple Trees: I. Relative Growth and Net Assimilation Rates in 1- and 2-year-old trees of teh Apple Rootstock-vriety M.XIII

Two series (A and B) of one-year-old rooted-stems were plantedin consecutive seasons and samples were lifted at intervalsof a few weeks over periods of one year (A) and two years (B)respectively. The weights at lifting, and their logarithms,were adjusted by covariance with the corresponding values atplanting. Net Assimilation Rates, on the leaf-weight basis,showed values and a downward trend similar to those reportedfor cotton in the Sudan. The values on the bases of the arithmeticand geometric means were rather different and suggested differentinterpretations. The mean leaf-weight ratios, starting as nileach season, rose to a maximum, never exceeding 20 per cent.,by mid-summer. The Relative Growth Rates in the second season(B) started low and fell to a very low value; in the first seasonof both series they were low from the start—probably becauseof a check at planting. It is suggested that the low valuesof the R.G.R. found here, and reported elsewhere for other woodyplants, and the low leaf-weight ratios, are due largely to thepresence of much residual tissue at the start of the seasonand that it is the leaf/(total-increment) rather than leaf/(total-weight)that is comparable to the leaf-weight ratio in annuals. It ispointed out, however, that other factors seem to be involved.     

Interrelation of Scion and Rootstock in Fruit-trees: I. Weights and Relative Weights of Young Trees formed by the Reciprocal Unions, as Scion and Rootstock, of Three Apple Rootstock Varieties: M.IX, M.IV, and M.XII

Three apple rootstock varieties, M. IX, M. IV, and M. XII, werecombined as scion and rootstock in all nine ways and sampleswere harvested at intervals over 3 years. Their relative sizeson each occasion and their relative rates of growth betweenoccasions were determined by calculating the ratios betweenthe geometric mean weights. The ratio of the products of thesefor trees with reciprocal Unlike unions, e.g. IX/XIIx XII/IX,to that for trees with Like unions of the component varieties,e.g. IX/IX x XII/XII, was slightly but not significantly lessthan unity. Composite trees, e.g. IX/XII, resembled in sizethose of the rootstock type, e.g. XII, more than the scion variety,IX, though this had some influence.