Tuz stresi altındaki biber bitkilerinin fizyolojik ve histolojik yanıtlarına triptofan’ın etkisi

Öz

Tuz stresi bitki fonksiyonlarını olumsuz yönde etkileyen önemli bir abiyotik stres faktörüdür. İndol-3-asetik asit (IAA) öncüsü olan triptofan, tuz stresi altında bitki büyümesinde önemli bir rol oynamaktadır. Bu çalışma, tuz stresine maruz kalan genç biber bitkilerinde farklı triptofan dozlarının (L-tr) etkilerini ortaya koymayı amaçlamıştır. Tuzluluk stresi öncesinde bitki köklerine kontrol ve tuz uygulamaları hariç olmak üzere 3 triptofan dozu uygulanmıştır. Daha sonra kontrol dışındaki tüm bitkilere sulama sırasında 150 mM tuz stresi (NaCl) uygulanmıştır. Çalışma, tuz stresi uygulaması başladıktan 35 gün sonra sona erdirilmiştir. Yapılan ölçümler arasında histolojik (korteks ve hücre çapları, ksilem ve orta damar çapları, epidermis kalınlığı) ve fizyolojik (yaprak su içeriği, membran geçirgenliği, klorofil ve karotenoid konsantrasyonları, toplam fenolik içerik) parametrelerde önemli farklılıklar kaydedilmiştir. Bu parametrelerin değerlendirilmesi triptofanın (L-tr) ozmotik düzenleme üzerindeki olumlu etkisini ortaya çıkarmıştır. L-tr uygulamaları tuz stresine göre ksilem, midrip, korteks hücre çapları ile epidermis ve korteks kalınlığını artırırken, korteks hücre sayısını azaltmıştır. Özellikle, NaCl + L-tr 100 µM uygulaması, kontrole kıyasla ksilem kanal çapında %25'lik bir artış, midrip çapında %30’luk bir artış ve epidermis kalınlığında %15'lik önemli bir artış göstermiştir. Genel olarak, NaCl + L-tr 100 µM uygulaması, çeşitli parametrelerde kontrollere en yakın değerleri sergilemiştir. Bu çalışma, biber bitkilerinde tuzluluk stresinin azaltılmasında L-tr'nin potansiyel faydasını ortaya koymaktadır.

Anahtar Kelimeler

• Capsicum annuum
• Korteks
• Tuzluluk
• Triptofan
• Ksilem

Impact of tryptophan on physiological and histological responses of pepper plants under salt stress

Abstract

Salt stress is a significant abiotic stressor adversely affecting plant functions. Tryptophan, a precursor to IAA, plays a crucial role in plant growth under such stress. This study investigated the effects of different tryptophan doses (L-tr) on young pepper plants subjected to salt stress. Preceding salinity stress, three L-tr doses were administered to plant roots, excluding control and salt applications. Subsequently, all plants except controls received 150 mM salinity (NaCl) during irrigation. The experiment concluded after 35 days post-salinity treatment. Significant variations were noted in histological (cortex and cell diameters, xylem and midrib diameters, epidermis thickness) and physiological (leaf water content, membrane permeability, chlorophyll and carotenoid concentrations, total phenolic content) parameters among treatments. Evaluation of these parameters revealed L-tr’s positive impact on osmotic regulation. L-tr applications increased xylem, midrib, and cortical cell diameter, cortex, and epidermis thickness compared to salt stress, while cortical cell number also decreased. Particularly, NaCl + L-tr 100 µM treatment exhibited a 25% increase in xylem conduit diameter, a 30% increase in midrib diameter, and a significant 15% increase in epidermis thickness compared to controls. Overall, NaCl + L-tr 100 µM treatment displayed values closest to controls across various parameters. This study suggests the potential utility of L-tr in mitigating salinity stress in pepper plants.

Keywords

• Capsicum annum
• Cortex
• Salinity
• Tryptophan
• Xylem

Kaynakça

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