En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
59 ratings

Monday - November 21, 2005

From: Newark, DE
Region: Mid-Atlantic
Topic: General Botany
Title: Process of transpiration in plants
Answered by: Nan Hampton and Joe Marcus

QUESTION:

I'm in 6th grade and I have a science project to do and the question is, Do living plants give off moisture. The first part of my project is to explain how living plants give off moisture. I've checked Google and Ask Jeeves, but I can't find my answer. Can you please help me? Thank you,

ANSWER:

Plants do give off moisture in a process called transpiration. The major way the plant does this is through special holes, or pores, on the leaf surface called stomata (singular, stoma). These stomata must open for the plant to take in the carbon dioxide (CO2) that is crucial to its survival and growth. The stomata open and close dependent on the shape of the two guard cells on either side of the stomatal pore. The guard cells respond to water pressure. When there is plenty of water present and the pressure in the guard cells is high, their shape changes so that the pore of the stomata is open and the plant can take in CO2. When it is open the stomata can also transpire, or lose water. How much water it loses depends on the surrounding temperature, humidity, and air movement. When there is little water pressure in the guard cells, they close and the plant ceases to transpire (as well as to take in CO2). Closing the stomata conserves water for the plant.

Some water can also be lost simply through the surface, or cuticle, of the leaf as well as through the stomata. However, because the cuticle has a waxy surface that prevents the water passing through it, this is usually a very small fraction of transpiration. In some plants there is a very heavy waxy deposit on the cuticle that gives extra protection to keep the plant from drying.

The number and placement of the stomata in the leaves also affects how much the plant transpires. Many species of plants have fewer stomata per square centimeter on the upper surface of the leaves than they have on the relatively protected under surface. Other species have stomata only on the under surface of the leaf where there is more protection from heat and air movement that can increase transpiration.

Here are several Internet sites that give you more information on plant transpiration:

1. University of Arizona Cooperative Extension
2. University of Wisconsin Earth Online
3. University of Michigan Reach Out!

 

More General Botany Questions

Forestiera pubescens blooming in July
August 07, 2012 - I have a lot of what appears to be Forestiera pubescens. They are covered with the dark blue/black berries and flowers. Apparently they are blooming again in the middle of July. I live about 35 mile...
view the full question and answer

Plants for soils with extreme pH values
May 24, 2009 - I am doing a project on acid and alkaline on the ph scale but all I can find is a range of 5.0 to 8.0. Do they have plants in the range of 8.0 to 14.0 or 1.0 to 5.0? If not, why is that? If so, what a...
view the full question and answer

Information about Erigeron annuus and Erigeron philadelphicus
January 10, 2015 - Hi! I am looking for information about the specific leaf area of Erigeron annuus and Erigeron philadelphicus. Do you know of anyone who is working with any these species, who might be able to provide...
view the full question and answer

Can plants in the same genus cross-pollinate?
March 27, 2009 - Can you cross-pollinate plants from the same genus?
view the full question and answer

Plants for a hillside in WI
February 18, 2012 - I live in Wisconsin and am currently doing a research project on plant variation on the north and south sides of a hill. I was wondering you could suggest any books to me that would address this issue...
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP | STAFF
© 2015 Lady Bird Johnson Wildflower Center