TREE PHYSIOLOGY 



221 



nutrients, however, do not flow into the plant in a water 

 stream, but their intake depends upon their solubility and 

 their relative concentration within and without the plant. 

 Whenever their concentration is higher in the soil solution, 

 they diffuse into the plant. If it were not for water, these 

 foods would not be transported up through the plant. Water, 

 again, is necessary in the formation of the carbohydrates, 

 proteins, fats, etc., and their translocation down from the 

 leaves to all parts of the branches, fruit, trunk, and roots. 

 Large amounts of water are likewise transpired daily. About 

 500 pounds of water are transpired for each pound of dry mat- 

 ter produced, and fruits contain from 85 to 90 percent water. 

 Such troubles as cracking of fruit, water core, fruit pit, eork„ 

 drought spot, and die-back are all exaggerated by improper 

 water relations. Each vigorous, mature apple tree uses from 

 15 to 20 tons of water per year when it is making a good 

 growth and producing a good crop. 



On the other hand, it is possible to have too much soil mois- 

 ture available for good tree growth and fruitfulness ; then trees^^ 

 suffer from what is commonly known as 'Vet feet.^' Orchards" 

 planted in ground that remains wet during most of the year^ 

 especially if the water table is close to the surface, grow and 

 fruit very poorly, and are easily injured by cold weather. 

 Such soils are poorly aerated and do not warm up, bacterial 

 action in the soil is practically prevented, and the roots of 

 fruit trees either make very little growth or die. Of course 

 orchards should not be planted under such conditions, but 

 they are occasionally found. If the conditions are not too 

 hopeless, thorough soil drainage will produce wonderful results. 



Relation of Amounts of Carbohydrates and Nitrogen, Not 

 only are the amounts of carbohydrates and nitrogen important 

 in influencing growth and fruitfulness, but the relative propor- 

 tions of these in the plant seem to be very important. 



In general, plants may be grouped into four classes, de- 

 pending upon their growth and fruitfulness, and the propgrtioDL 

 of carbohydrates and nitrogen in their tissues. 



