Harry F. Clements 459 



Soil moisture, being the source of plant moisture, is of course primary, 

 but there are other factors which are important in determining the 

 moisture level of the tissues. However, in these studies the soil moisture 

 was maintained well above the wilting point throughout the crop ex- 

 cept toward the end when the crop was put on a drying schedule. 



Under these circumstances the dominant factor affecting the moisture 



TABLE V 

 Partial Regressions of Certain Factors on Sheath Moisture 



(" = 1373) 



Factor 



Leaf nitrogen 



Maximum temperature 



Age 



Light 



Relative humidity 



Soil moisture 



Wind velocity 



R= .846 



level is the nitrogen level. The strong positive relation between maxi- 

 mum temperatures of the air and the moisture level may be somewhat 

 surprising but shouldn't be so when it is remembered that low soil 

 temperatures which follow air temperatures may result in actual desic- 

 cation of the plants even though soil moisture is adequate. Light is 

 strongly negative in its influence on tissue moisture, as is age. The hu- 

 midity relationship is strongly positive as it should be, and it appears 

 that this factor has not been given enough attention in the past. In this 

 analysis wind velocities are comparatively minor but are shown to be 

 positive. However, in the Islands high winds are associated with 

 stronger light intensities and lower humidities and, thus, the influence 

 of wind may be masked, especially since the area in which this study 

 was carried on is not a high wind area. 



In Table VI a similar analysis of factors affecting the nitrogen level 

 is shown. 



