124 COCONUT PLANTER'S MANUAL 



called carbon-dioxide. This gas is brought down from the atmosphere 

 dissolved in rainwater; it is also exuded from the root of plants as a 

 result of their breathing process and it is given off from decaying vege- 

 table matter in the soil. "When dissolved in water it has the effect of 

 making it a much more powerful solvent than pure water, and in this 

 way larger quintities of plant-food are taken into solution. 



The Function of the Leaves. 



Three separate and distinct functions are carried out by the leaves 

 of the coconut palm, viz., Transpiration, Respiration and Carbon 

 Absorption. 



Transpiration is concerned with getting rid of the huge quantities 

 of water absorbed by the roots. This is effected by evaporating the 

 water from the surface of the leaves into the atmosphere in the form 

 of vapour or steam. 



Tlie water absorbed by the roots contains dissolved in it various 

 substances which are essential for the nutrition of the palm ; and 

 between the root-ends, where the water enters, and the leaves, where 

 the hulk of it escapes into the air, there is a continuous upward move- 

 ment of a stream of water through the roots, stem and branches of the 

 palm, and by this means the substances dissolved in the water are 

 carried up to the leaves where they are left and utilized, only pure water 

 being allowed to escape in the process of transpiration. 



The practical importance of this process lies in the fact that the 

 speed of transpiration governs the amount of plant-food absorbed by 

 the roots, if transpiration is checked then the upward How of water 

 stops and the loots cease to absorb plant-food, whereas if transpiration 

 is encouraged and hastened then the upwards flow of water moves more 

 quickly and tne roots absorb water and plant-food more vigorously. 



' The chief factors which affect transpiration are the following: — 



1. The intensity of the light to which the palm is exposed. 



2. The dampness of the surrounding atmosphere. 



3. The amount of water in the soil and the quantity and nature of 

 the substances dissolved in it. 



The brighter the light to which the palm is exposed the greater will 

 In the transpiration. It has been estimated that transpiration is at 

 least a hundred times as great in bright sunshine as it is in the dark. 



Even a light haze obscuring the sun will reduce Transpiration by as 

 much as twenty-five per cent., while a cloud heavy enough to conceal 

 the sun will cut it down to about a quarter of what it is in direct sunlight. 



