Published May 2004 (Rev May 2007)

Growing Points of Interest

URL: http://www.kingcorn.org/news/timeless/GrowingPoints.html

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address:
 

• Recovery from early season damage to corn is often dependent on the health of growing point region.

here is something about 30 mph winds and sand/grit/soil blasting across corn fields at seedling height that makes one curious about the ability of corn to recover from early season damage.  The same can be said following a thunderstorm accompanied by strong winds and damaging hail (Nielsen, 2007b). Whenever corn is damaged early in the growing season, growers are sometimes faced with the decision of whether or not to replant the field. 

One of the most important, and most difficult, steps in making a replant decision is estimating the surviving plant population in the field.  Corn is remarkably resilient to aboveground damage early in the season, yet growers often underestimate the ability of corn to recover from such damage.  Consequently, much of the replanting that occurs each year is a waste of money and effort.  Use the worksheet in my replant publication (AY-264-W) to estimate yield and dollar returns to corn replanting. 

The health and condition of the corn plant’s growing point (apical meristem) plays a major role in determining whether a damaged corn plant will recover or not. A plant damaged aboveground but with a healthy, undamaged growing point will usually survive.  However, damage to the growing point area will either kill the plant or severely stunt its recovery. 

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The growing point is that meristematic area of the corn plant where leaves and, eventually, the tassel are initiated. Morphologically, the growing point area is located near the top of the young plant’s stalk tissue. Prior to stalk internode elongation, the growing point is initially located 1/4 to 3/4 inch below the soil surface, near the crown of young seedlings at growth stages VE (emergence) to about V4 (four leaves with visible leaf collars [Nielsen, 2007a]). 

The growing point remains below ground until V5 to V6. Stalk internodes begin to elongate shortly before V5, eventually elevating the growing point above the soil surface. From this point forward, the growing point becomes increasingly exposed and vulnerable to aboveground damage.

Prior to V6, while the growing point is belowground, corn can tolerate quite a bit of aboveground injury from “single event” damage by frost, hail, wind, cutworm feeding, sandblasting, tire traffic, 28% N solution burn, etc. However, repeated injury to young plants (e.g., multiple days of sandblasting) or extended periods of sub-optimal temperatures (i.e., “darned” cold weather) and cloudy conditions following the damage may prevent photosynthetic recovery (renewal of green leaves) long enough to eventually kill the plant even though the growing point is technically not injured. 

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While corn younger than V6 can tolerate a fair amount of aboveground frost damage to exposed leaf tissue, lethal cold temperatures (28F or less for several hours) can “penetrate” the upper soil surface (especially dry soils) and damage or kill the growing point of a young corn plant. Corn younger than V6 is also susceptible to belowground damage from soil insects, disease, and flooding or ponding. 

Human nature being what it is, most growers can’t avoid walking damaged corn fields the day of or the day following the injury to begin assessing the consequences of damage to their corn field. Unfortunately, most of the time a fair assessment of the recovery potential of damaged plants cannot be made that soon. Damaged corn fields need to be left alone for several days, sometimes up to a week, after the damage occurs to give the plants some time to exhibit visible recovery.

Splitting open a damaged corn plant is a time-honored practice when assessing the consequences of early-season damage to corn. The stalk tissue near the growing point region should remain firm and yellowish-white, as should the growing point region itself.  Discolored or mushy tissue near the growing point usually spells trouble for the injured plant. Injury that occurs close to the growing point area (e.g., hail damage, stinkbug feeding) may alter normal hormonal activity and eventually cause deformed regrowth of stalk or leaf tissue.

Visible recovery of leaf development from the whorl of surviving plants will be evident within 3 to 10 days after a damage event, depending on temperature and soil moisture conditions. Warmer temperatures and adequate soil moisture encourage rapid recovery, while cooler temperatures and/or drought stress slow the rate of recovery. Given sufficient time, surviving corn plants will exhibit new leaf tissue expanding from the whorls, while dead corn plants will still look, well… dead.

Related References:

Nielsen, R.L. (Bob). 2003 (rev.) Estimating Yield and Dollar Returns to Corn Replanting. Purdue Univ. Coop. Ext. Service Pub. No. AY-264-W. [On-Line]. Available at http://www.agry.purdue.edu/ext/pubs/AY-264-W.pdf. (Verified 5/27/07). 

Nielsen, R.L. (Bob). 2007a. Determining Corn Leaf Stages. Corny News Network, Purdue Univ. [On-Line]. Available at http://www.kingcorn.org/news/timeless/VStageMethods.html. (Verified 5/27/07).

Nielsen, R.L. (Bob). 2007b. Recovery From Hail Damage to Young Corn. Corny News Network, Purdue Univ. [On-Line]. Available at http://www.kingcorn.org/news/timeless/HailDamageYoungCorn.html. (URL verified 5/27/07).