74 FUNDAMENTALS OF FRUIT PRODUCTION 



lightly irrigated plots in Oregon. ^^ Barss^ observes that Bartlett pears 

 from trees well supplied with moisture are a clear green at picking time; 

 those from trees suffering for lack of moisture he describes as bluish-gray 

 green. Increased moisture may lead indirectly to poorer color of varieties 

 of apples, pears and peaches that have more or less red coloring matter 

 in their skin by producing a larger wood and leaf growth and thus 

 more shade, the formation of the red pigment in these cases being depen- 

 dent upon sunlight reaching the fruit itself. Though this effect of soil 

 moisture is noted only late in the season as the fruit is maturing, it is 

 not an effect of surplus moisture at that time or just previous, but is 

 rather to be attributed to surplus moisture during the spring months 

 when most of the shoots and leaves are developed. Thus trees with 

 fruits showing the effects of drought in poor size and quality may at the 

 same time show the effects of too much moisture during the spring months 

 in poor color. Such a condition suggests the contrasting extreme, namely 

 high color from good exposure to the light incident to proper foliage and 

 shoot development early in the season and good size and quality incident 

 to abundant moisture late in the season. Either extreme can be produced 

 or at least approximated by skillful culture, particularly in irrigated 

 sections where water supply is under control. 



Composition. — That the composition of fruit is influenced materially 

 by water supply is suggested by the large percentage of water in the 

 tissues of the fruit. It is probable, however, that the most important 

 influence of soil moisture upon quality and composition is not in modi- 

 fying its water content, but rather in its effect upon other constituents. 

 Thus the poor quality of strawberries ripening during or immediately 

 after a rainy period is due more to a low sugar than to a high water con- 

 tent. Exact figures are not available to show how chemical composition 

 of fruits varies with definite changes or variations in soil moisture, con- 

 ditions being otherwise the same, but it is presumable that such figures 

 would show material differences. Developing oranges may contain 25 to 

 30 per cent, less moisture during the middle of the day, when transpi- 

 ration is at its highest, than at night when it is at its minimum, ^^ but the 

 moisture content of apple leaves has been found to vary only from 62.8 

 per cent, to 64.8 per cent, when the soil moisture in the plots in which the 

 trees were growing ranged from 11 to 24 per cent.^^^ This suggests that 

 such extreme variations as have been found in the orange are only tempo- 

 rary and that the plant possesses a marked ability to construct its 

 tissues along a chemical pattern independent of available soil moisture 

 to a considerable degree. However, comparatively slight differences in 

 chemical composition are often responsible for large differences in flavor 

 or quality. In addition, differences in soil moisture may cause shght 

 differences in texture and in the size and cohesion of individual cells or 

 groups of cells, resulting in great differences in quality. The comparative 



