Auxin, The substance responsible for cell elongation is auxin. This phytohormone is formed in cells at the tip of the shoot and is then passed from cell to cell.
        
             
        
        
        
Answer:
The presence of predators of deer which does not allow increase in the population of deer year after year. 
Explanation:
In an forest ecosystem, one animal controls the population of another organisms and thus there is no increase in the population of that organism and the ecosystem is in equilibrium state. The population of deer did not increase due to the presence of predators such as lion, cheetah etc and the net population is 0.
 
        
             
        
        
        
Watershed is the place where water of rain and snow get stored. The watershed contains surface water-and wetlands--and all the underlying ground water,lakes, streams, reservoirs. Lake is the major component of the watershed . The watershed can be used for various purpose like dams, hydrological modification etc.
 
        
             
        
        
        
Which picture?, pls Clip the picture for the answer.