Two C2H 4-producing systems in cocklebur seeds

Area of Science:

• Plant Physiology
• Seed Dormancy Research
• Biochemistry

Background:

• Ethylene (C2H4) is a plant hormone involved in various developmental processes, including seed germination.
• Seed dormancy in cocklebur (Xanthium pennsylvanicum Wallr.) is a complex trait influenced by environmental and internal factors.
• Understanding ethylene production mechanisms is crucial for deciphering dormancy release.

Purpose of the Study:

• To investigate the ethylene (C2H4) production systems in embryonic axes and cotyledons of cocklebur seeds.
• To determine how these systems differ between dormant and non-dormant seeds.
• To correlate ethylene production with seed dormancy status and after-ripening.

Main Methods:

• Excising embryonic axes and cotyledons from dormant and non-dormant cocklebur seeds.
• Measuring ethylene (C2H4) production under varying ambient oxygen (O2) tensions.
• Analyzing the characteristics of quasi-anaerobic and aerobic ethylene-producing systems.

Main Results:

• Two distinct ethylene (C2H4) production systems, quasi-anaerobic and aerobic, were identified in both organs.
• Quasi-anaerobic activity was high in dormant seeds and decreased with after-ripening, especially in axes.
• Aerobic activity was low in dormant seeds, increased upon dormancy release, and was the sole system in non-dormant axes, while quasi-anaerobic remained dominant in cotyledons.

Conclusions:

• Ethylene (C2H4) production mechanisms vary significantly between seed organs (axes and cotyledons) in cocklebur.
• The dormancy state profoundly influences the activity of these ethylene-producing systems.
• Differential regulation of quasi-anaerobic and aerobic ethylene production contributes to the control of seed dormancy and germination.