Na+ , K + oranı Mısır (Zea mays L.) Yapraklarında Hücre Zarı H+ -ATPase Hidrolitik ve Pompalama Aktivitesini Etkiler mi?

Abstract

Tuzluluk bitki büyümesi ve tarımsal verimliliği sınırlar. Tuz stresinin ilk aşamasında, bitkilerin büyümesi ağırlıklı olarak ozmotik stresten ve az da olsa Na+ iyonundan olumsuz yönde etkilenir. Çalışmamızın amacı, Na+ un plazma zarı H+-ATPaz’ının hem hidrolitik hem de pompalama aktivitesini etkileyip etkilemediğini araştırmaktır. Sodyum tuzluluğu bitki içerisinde Na+/K+ oranında değişime neden olur buda K+ un azalmasına neden olur. Yüksek sitoplazmik Na+ konsantrasyonları ve düşük K konsantrasyonlarının plazma zarı H+-ATPaz aktivitesi üzerine etkisi vardır. Azalan H+-ATPaz aktivitesi apoplast asidifikasyonunda düşüşe neden olur. Bu süreç, hücre duvarı esnekliğini sınırlar ve tuz stresi sonrası büyüme azalır. Bu nedenle, hücre uzaması için önemli olan H+-ATPaz aktivitesi, farklı Na+/K+ oranlarının etkisi altında ölçülmüştür. Plazma membranları iki fazlı sulu polimer tekniği kullanılarak iki günlük mısır sürgünlerinden izole edilmiştir. ATPaz aktivitesi serbest kalan Pi nin ölçülmesi ile tespit edilmiştir. H+-pompalama aktivitesi akridin oranın absorbansı ile belirlenmiştir. İzole edilen hücre zarlarına in vitro koşullarında Na+ ve K+ verilmiştir. Sitoplazmik 100 mM yüksek Na+ konsantrasyonu, 100 mM K+ konsantrasyonu ile karşılaştırıldığında hidrolitik H+-ATPaz etkinliği %80’e düşerken, H+-pompalama aktivitesi %30’a düşmüştür

Keywords

• Zea mays, Na+/K+ oranı, Hücre zarı, H+-ATPaz, Yaprak gelişimi

Does the Ratio of Na+ and K+ Affect the Hydrolytic and Pumping Activity of the Plasma Membrane H+ -Atpase from Maize (Zea Mays L.) Shoot?

Abstract

Salinity limits plant growth and impairs agricultural productivity. In the first phase of salt stress, growth of plants is impaired predominantly by osmotic stress and only slightly by Na+ effects. The aim of our work was to investigate whether Na+ affects both hydrolytic and pumping activity of the plasma membrane H+ ATPase. Sodium salinity leads to a shift of the Na+/K+ ratio resulting in a displacement of K+ in the plant. It was shown that high cytoplasmatic Na+ concentrations and low K+ concentrations have an effect on the H+ ATPase activity of the plasma membrane. Reduced H+-ATPase activities caused a reduction of the acidification of the apoplast. This process limits the cell-wall extensibility and thus reduces growth after salt stress. For this reason, H+ATPase activity, which is important for cell elongation was measured under the influence of different Na+/K+ratios. Plasma membrane was isolated from two days old maize shoots using the aqueous polymer two-phase technique. ATPase activity was determined by measuring the release of Pi. The H+-pumping activity was revealed by absorbance quenching of acridine orange. Identical plant shoot material was used for ATPase extraction and effects of Na+ and K+ were tested in vitro. High concentration of 100 mM Na+ decreased the hydrolytic H+-ATPase activity to values of 80%, in comparison to high concentration of K+ (100 mM) without Na. However, under comparable conditions the H+ pumping activity was decreased to 30%

Keywords

• Zea mays, Na+/K+ ratio, Plasma membrane, H+-ATPase, Leaf growth

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