FEATURESTORY
by Ray Barkalow
Understanding
Transpirational Pull
When Watering
Orchids
W
ater travels from the potting
medium into the plant and
makes the journey upward into
the leaves, overcoming the
forces of gravity, and your cultural conditions
and watering habits can affect this. The force
at work is called transpirational pull, which
can be visualized by imagining sipping a
drink through a straw. Evaporation of water
through stomata (tiny openings in leaves) cre-
ates the suction, pulling water continuously
upward. The hotter, sunnier and less humid
the environment, the faster the evaporation
and the faster the transpirational pull. Prob-
lems begin when the rate of transpiration ex-
ceeds the ability of the roots to absorb water
and the plant wilts due to loss of turgor, or
water pressure within their cells. Such loss of
turgor is more difficult to see in most orchids,
due to the presence of unique rigid structures
throughout the plant that prevent the collaps-
MULTIPURPOSE GREENHOUSE
DISINFECTANT & DISEASE CONTROL
• Disinfect pots, trays, benches, tools, etc.
• Algae control on walkways, pots, evaporative coolers, soil
• Spray on plants to control bacterial, viral and fungal disease
• Excellent wetting agent
• Cost effective, pleasant odor and environmentally friendly
MARIL PRODUCTS, INC.
15421 Red Hill Ave. • Suite D • Tustin, CA 92780 USA
714-544-7711 • 800-546-7711 • www.physan.com
September 2018
www.GardenandGreenhouse.net
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