Causes of Purple Sorghum Seedlings
Purple Plants
Key Points
 Environmental and agronomic
stress can cause purplish
sorghum seedlings.
 Usually, stress related
sorghum purpling is not long
lasting.
 Cold temperatures are the
primary environmental cause
of sorghum purpling.
Environmental and agronomic stresses can cause sorghum seedlings to become
purplish (Figure 1). The cause of the purplish color is the result of an accumulation of
anthocyanin pigment, which is a sugar-containing molecule. The pigment is natural and
can occur without stress as it is responsible for purple grapes, red cabbage,
blackberries, autumn leaves, and other reddish-purple fruits, vegetables, and plants.
Individual sorghum products may be genetically more purplish in color from higher
levels of anthocyanin pigment.
In most instances, sorghum purpling caused by a stress is not long lasting and does
not result in the non-realization of genetic yield potential. However, if the cause is
severe compaction or another non-remediable cause, season-long problems may
occur that can result in the loss of economic yield.
Stress Related Purpling
Purple sorghum seedlings can result from a deficiency in phosphorus (P). The
coloration is the result of sorghum roots being unable to grow into and absorb
from insects, herbicides, and
non-mobile P, a condition often associated with cool temperatures. Usually the return
of warmer temperatures allows for ample root growth, P absorption, and the fading of
diseases can cause purpling.
the purple coloration without a lasting effect. If soil P is deficient or root growth is
 Yellow sugarcane aphids can
restricted by severe compaction, the roots may not be able to obtain or reach the P
causing the plant to remain purplish throughout the
cause purpling and plant
growing season. Season-long P unavailability can
death.
result in poor plant growth and reduced production.
Injuries to the root system by insects, herbicides, or
diseases can cause purpling. Depending on the injury severity, the roots may be able to
overcome these injuries with little, if any, effect on grain production. Severe injury could result in
prolonged P deficiency and water absorption.
Cold temperature stress slows the plant’s overall respiration ability, which can reduce its ability to
metabolize sugars created through the photosynthetic process. The produced sugars remain in
the leaves instead of being distributed throughout the plant and can cause purpling. The “stored”
sugars can also stimulate the formation of additional anthocyanin pigment.
Some anthocyanin genes are cold-induced.1 Therefore, cold temperatures can turn these genes
on and result in the production of the purple pigment.
Feeding by yellow sugarcane aphids can also cause purple discoloration in seedling sorghum
Figure 1. Purplish sorghum seedlings
through an injected toxin. As few as 5 to 10 aphids per leaf can kill 18-inch tall sorghum plants.
resulting from restricted root growth.
Careful scouting should be exercised to determine if they are the cause of the purpling.
 Compaction and root injury
Sources:
1
Christie, P.J., Alfenito, M. R., and Walbot, V. 1994. Impact of low– temperature stress on general phenylpropanoid and anthocyanin pathways: Enhancement of transcript abundance and
anthocyanin pigmentation in maize seedlings. Planta. 194:541-549.
Other sources: Gerik, T, Bean, B., and Vanderlip, R. 2003. Sorghum growth and development. B-6137. Productive Rotations on Farms in Texas Profit. Texas Cooperative Extension. The
Texas A&M University System.
Studebaker, G.E., Lorenz, G., and Akin, S. Grain sorghum insect control. FSA2066. Agriculture and Natural Resources. University of Arkansas.
Peter, M. L. 2001. Young sorghum, corn plants reacting to recent weather. (News Release citing Fjell, D.) K-State Research and Extension. Kansas State University. www.ksre.ksu.edu/
news/sty/2001/sorghumcorn weather.htm. Web sources verified 5/19/2015.
This publication was developed in partnership with Technology, Development & Agronomy by Monsanto.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and
weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Channel®
and the Arrow Design® and Seedsmanship At Work® are trademarks of Channel Bio, LLC. All other trademarks are the property of their respective owners. ©2015 Monsanto Company.
150513083949 05272015LGM
Channel.com
For additional agronomic information, please contact your Channel Seedsman