Crafts et al. — 208 — Water in Plants 



Disease may disrupt metabolism and result in sluggish stomatal response to chang- 

 ing environment; increased transpiration may result. Insecticides may reduce trans- 

 piration by interfering with diffusion, or increase it by wedging the stomata open. 

 Copper sprays increase transpiration by increasing the permeability of the cuticle. 



Excessive water loss by nursery stock may be prevented by hardening the plants, 

 coating with wax, and avoiding any conditions tending to enhance rapid evaporation. 



Water deficits affect the physiology of plants by stimulating hydrolysis and in- 

 hibiting condensation reactions. These responses are brought about by the effect of 

 water balance on enzymatic activity. Starch dissolution during wilting is a common 

 reaction of this type. Water deficit may also affect reproductive processes. 



Subaqueous transpiration has been explained as due to faulty experimental technic, 

 water secretion by leaf cells, and the functioning of the mass-flow mechanism of phloem 

 transport. 



Transpiration is important in the physiology of plants as it relates to movement of 

 mineral and organic nutrients, to the supply of water for metabolic needs, and to its 

 secondary effects upon growth and development as these integrate the complex rela- 

 tions of the plants' physical environment. Under many conditions the health of plants, 

 and hence the well-being of man, depends upon the efficient utilization of the available 

 supply of water. 



