A discussion of the present status of the various indices of maturity as 
well as new techniques of maturity evaluation follows. 
Physical Aspects 
Size and Weight 
Lott (42) showed that a decided change in the color of skin of Trans- 
parent and Duchess apples measured by reflectance spectrophotometry was 
accompanied by a rapid increase in size and weight of the fruit. 
Lott (44) points out that there is rapid cell division in the early 
developmental stages of maturity terminating 3 to 4 weeks after bloom. During 
this time the cell walls are thin and cell enlargement is taking place. In 
midseason, cells cease to divide, cell walls become thicker, cells enlarge and 
intercellular spaces develop, and the cuticle thickens. Finally, with matura- 
tion, cell walls become thinner, cells continue to grow, and intercellular 
spaces increase, 
Bain and Robertson (2) showed, at least with the Granny Smith apple 
variety, that as long as the fruit stayed on the tree cell enlargement con- 
tinued and that after 205 days from full bloom, cell size and average weight 
of the fruit were still increasing. 
Robertson and Turner (67) thought that marked changes in carbohydrate 
content of Granny Smith apples (dry weight increasing more rapidly than cell 
size) made dry weight studies unsuitable as a basis of expression of growth 
associated with cell enlargement. They thought fresh fruit weight was more 
suitable but was fraught with problems of sampling error. 
Martin (51) pointed out that increase in size of Cox, Jonathan, and 
Sturmer apple varieties was accompanied by more rapid acid loss, starch con- 
version, and perhaps softening and slower accumulation of soluble solids. On 
the other hand, he said that as Cleopatra variety fruit increased in size acid 
was higher and starch loss lower. No explanation could be offered for the two 
conditions, but he states that it is probable that the Cox, Jonathan, and 
Sturmer varieties were growing faster than material could be transported. The 
lower acid concentration and soluble solids were due to dilution and earlier 
starch conversion from utilization of resources to meet growth needs. In 
Cleopatra, supplies were apparently adequate to keep pace with expansion, 
While such variability is apparent and minimizes the value of size and 
weight as a means of differentiating maturity, Lusis (48) was able to show that 
specific weight determination of German apple varieties by hydrostatic method 
can be taken as a measure for determining the stage of maturation especially in 
fruit for storing. 
West (89) showed graphically an increasing weight relationship with 
fruit ontogeny and a flattening of the growth curve as optimum maturity was 
approached, This study gave some credence to weight relationships of the 
apple as a guide to maturity. 
Martin (51) also pointed out that the direct correlation of size with 
breakdown, deep scald, or Jonathan spot might be due to the direct relation of 
size and maturity factors shown for Cox and Jonathan as these disorders tend to 
increase with increasing maturity. This could not be the case for the direct 
relation of size and bitter pit in Cox and Sturmer varieties because bitter pit 
incidence decreases with maturity. 
