Reducing sugars: a potential factor for onion plant salinity adaptation

Area of Science:

• Plant Science
• Agricultural Science
• Biochemistry

Background:

• Salinity stress is a major agricultural challenge, reducing crop yield by disrupting plant physiology.
• Sugars are known osmoprotectants, but their specific role in onion (Allium cepa L.) salinity adaptation requires further investigation.

Purpose of the Study:

• To evaluate the efficacy of foliar-applied reducing sugars (glucose, lactose, melibiose, xylose) in mitigating salinity stress in onions.
• To analyze the physiological, biochemical, and elemental responses of onions under varying salinity levels and sugar treatments.

Main Methods:

• Pot-grown onions were subjected to salinity stress (0, 75, 125 mM NaCl) with foliar application of 10 mM sugars.
• Measurements included growth parameters, photosynthetic pigments, osmoprotectants, oxidative stress markers, antioxidant enzymes, and elemental composition.

Main Results:

• Salinity significantly reduced onion growth; sugar treatments, especially lactose, markedly improved fresh weight.
• Xylose and melibiose preserved photosynthetic pigments (chlorophyll a and b).
• Melibiose and xylose increased osmoprotectants (proline and reducing sugars), while lactose reduced oxidative stress markers and enhanced antioxidant enzyme activities (PAL, PPO).
• Lactose and melibiose improved key mineral ratios (Ca²⁺/Na⁺, K⁺/Na⁺).

Conclusions:

• Foliar application of lactose and melibiose shows significant potential for enhancing onion salinity tolerance.
• These sugars improve osmoprotection, antioxidant capacity, and ion homeostasis, offering a viable strategy for salt-affected agriculture.