Introduction: Small changes in temperature can have dramatic effects on the rate of physiological processes. In general, a process will be two to four times faster if the temperature is increased 15 to 20 degrees Fahrenheit. On the other hand, a process will be two to four times slower if the temperature is decreased 15 to 20 degrees Fahrenheit. For example, consider data in the following tables.

Effect of temperature on flower deterioration rate and end-user life:

Temperature		Relative deterioration	Relative life
ºC	ºF	rate	percent
0	32	1.0	100
10	50	3.0	33
20	68	7.5	13

Thus, a carnation held at 50 degrees Fahrenheit, instead of its proper storage temperature of 32 degrees Fahrenheit, will deteriorate at least three times faster.

Transpiration: Most plants contain about 80 to 95 percent water. Water is the medium through which every biological reaction takes place. It also regulates temperature and promotes nutrient uptake through the roots.

Transpiration is the loss of water vapor by plants. Plants would die because of temperature extremes if water were not lost in this cooling process. Also, if water were not lost from flowers, solution could not be pulled up through the stems. Since transpiration takes place mostly through small openings or "stomata" in leaves, some flowers sold without leaves are prone to bent neck problems (i.e. gerbera). In addition, such flowers don't benefit from fresh-flower food solutions because they take up little solution (i.e. anthurium).

Transpiration is needed for proper post-harvest performance, but it must be controlled to prevent wilting. When water loss is greater than water uptake, plants and flowers wilt. High temperatures and high air movement can increase transpiration rates and hasten wilting.

* Adapted from Maxie, et al, 1973.

Information reprinted from SAF Flower and Plant Care Manual, (Society of American Florists: Alexandria, VA, 1994), pp. 145-146.