CHAPTER VIII 



THE PLANT AS AFFECTED BY UNFAVORABLE 

 TEMPERATURE 



The plant has now been grown, or well started on its 

 way. We must now determine what hindrances, acci- 

 dents or injuries may stand in the way or overtake it. We 

 may consider this subject, in successive chapters, under 

 the heads of temperature, unfavorable moisture supply, 

 unfavorable light and winds, insufficient or injurious food 

 supply and parasites. 



180. Factors of enviromnent. — The plant environ- 

 ment is mostly comprehended by the terms climate, 

 soil, animals and other plants. But as these are more or 

 less complex influences, it is well to analyze them and to 

 consider separately the component factors of each. 



THE PLANT AS AFFECTED BY EXCESSIVE HEAT 



181. Relation of heat to transpiration. — Transpiration 

 increases with the degree of heat. The most common 

 effect of heat upon plants is the drooping of the foliage, 

 due to excessive transpiration (74). With insufficient 

 water, this may occur at a temperature that is normal for 

 the plant. But with a water supply that is suflBcient at 

 ordinary temperatures, transpiration may be so much 



109 



