Light interacts with auxin during leaf elongation and leaf angle development in young corn seedlings

Area of Science:

• Plant Physiology
• Agronomy
• Genetics

Background:

• Modern corn (Zea mays L.) varieties are selected for high productivity in dense plantings.
• Physiological changes, including altered responsiveness to auxin and light, may underlie this selection.
• Differences in etiolated seedling morphology exist between modern (3394) and older (307) corn hybrids.

Purpose of the Study:

• To investigate if selection for increased crop yield in modern corn hybrids involves changes in auxin and light responsiveness.
• To compare the physiological responses to auxin and light between a modern hybrid (3394) and an older hybrid (307).

Main Methods:

• Comparison of etiolated seedling growth (coleoptile, mesocotyl, leaf) between hybrids 3394 and 307.
• Assessed responsiveness of seedlings and isolated segments to auxin and N-1-naphthylphthalamic acid (NPA).
• Evaluated the effects of light (white, red, far-red, blue) and NPA on elongation growth and leaf declination.

Main Results:

• Etiolated seedlings of modern hybrid 3394 were shorter, with reduced responsiveness to auxin and NPA compared to older hybrid 307.
• Hybrid 3394 exhibited less growth reduction by light and reduced inhibition of polar auxin transport (PAT) by NPA.
• Modern hybrid 3394 displayed more erect leaves, with altered responses to light and NPA compared to hybrid 307.

Conclusions:

• Auxin and PAT are involved in corn seedling elongation and light-mediated growth regulation.
• Reduced auxin responsiveness and altered light interaction in modern hybrid 3394 may result in more erect leaves.
• More erect leaves in 3394 likely contribute to its tolerance to dense planting, enhancing crop yield.