Humik Asit ve Liken Türevli Endofitik Bakterilerin Kombine Uygulaması, Yoncada (Medicago sativa L.) Tuz Stresi Kaynaklı Oksidatif Hasarı Yatıştırır

Öz

Bu çalışma, leonardit kaynaklı humik asit (HA) ile liken kökenli bir endofitik bakteri (Bacillus wiedmannii) arasındaki sinerjik etkinin, yonca bitkisinde (Medicago sativa L., cv. Konya) tuz stresini hafifletmedeki rolünü araştırdı. Yonca tohumları, 100 mM NaCl, HA (500 veya 1000 mg L-1) ve B. wiedmannii’nin farklı kombinasyonlarını içeren turba-perlit karışımında ekildi. 35 gün sonra, bağıl su içeriği (RWC), reaktif oksijen türleri (H2O2, O.-), MDA (malondialdehit), antioksidan enzim aktiviteleri ve fotosentetik pigment düzeyleri ölçülmüştür. Tuz stresi, tek başına uygulandığında RWC, fotosentetik pigment miktarı ve antioksidan enzim aktivitelerinde azalmaya, H2O2, O.-, ve MDA birikiminde ise artışa neden olmuştur. HA veya B. wiedmannii tek başına bu olumsuz etkileri kısmen hafifletmiştir. Ancak, özellikle 1000 mg L-1 HA+B. wiedmannii+NaCl kombinasyonu, RWC’yi artırmış ve ROS ile MDA seviyelerini kontrol grubuna yakın düzeylere düşürmüştür. Ayrıca, bu kombine uygulama antioksidan enzim aktiviteleri ile fotosentetik pigment içeriklerini, sadece tuz uygulamasına kıyasla artırmıştır. Bu sonuçlar, HA ile B. wiedmannii arasındaki sinerjik etkinin, su dengesini iyileştirerek, oksidatif zararı azaltarak ve antioksidan savunma sistemlerini aktive ederek tuz stresini hafiflettiğini göstermektedir. Bu nedenle HA ve B. wiedmannii’nin birlikte uygulanması, yem bitkilerinde tuz toleransını artırmak için umut verici bir strateji olarak değerlendirilebilir.

Anahtar Kelimeler

• Tuz stresi
• Yonca
• Humik asit
• Endofit
• Antioksidan
• Liken

Combined Humic Acid and Lichen-Derived Endophytic Bacteria Application Alleviates Salt Stress-Induced Oxidative Damage in Alfalfa (Medicago sativa L.)

Öz

This study investigates the synergistic effects of leonardite-sourced humic acid (HA) and a lichen-derived endophytic bacterium (Bacillus wiedmannii) in mitigating salt stress in alfalfa (Medicago sativa L., cv. Konya). Alfalfa seeds were grown in a peat-perlite mix with different combinations of 100 mM NaCl, HA (500 or 1000 mg L-1), and B. wiedmannii. After 35 days, relative water content (RWC), ROS (H2O2, O₂.-), MDA, antioxidant enzyme activities, and photosynthetic pigments were measured. The salt stress alone reduced RWC, the photosynthetic pigment amount, and the antioxidant enzyme activities, while elevating H2O2 and O2.-, and MDA accumulation. HA or B. wiedmannii (Bw) individually partially ameliorated these effects, however, the combined HA+Bw treatment under saline conditions (especially 1000 mg L⁻¹ HA+Bw+NaCl) elevated RWC, and reduced ROS and MDA levels close to the control values. In addition, the antioxidant enzyme activities and the photosynthetic pigment contents were enhanced under the combined treatments compared to the salt alone. These results demonstrate a synergistic effect between HA and B. wiedmannii in alleviating salt stress in the alfalfa by enhancing water status, reducing oxidative damage, and activating antioxidant defenses, suggesting that the co‐application of HA and B. wiedmannii is a promising strategy for improving salt tolerance in forage crops.

Anahtar Kelimeler

• Salt stress
• Alfalfa
• Humic acid
• Endophyte
• Antioxidant
• Lichen

Kaynakça

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