Bor elementinin bitkiler için önemi

Öz

Bitkilerde bor noksanlığı, en çok kumlu ve organik maddesi düşük olan, yıkanmanın fazla olduğu ve kireçlemenin sıklıkla yapıldığı asit topraklarda ortaya çıkar. Ayrıca, bor adsorpsiyonu/fiksasyonu yüksek olan killi ve pH’sı yüksek topraklarda da bor noksanlığına rastlanmaktadır. Bor noksanlığının ortaya çıkışıyla birlikte öncelikle hücre duvarlarının oluşumu, yapısal bütünlüğü ve işlevi zarar görmektedir. Bitkilerdeki borun yaklaşık % 90’a varan bölümü, hücre duvarlarında yapısal bir element olarak yer almakta ve biyolojik membranların stabilitesini korumaktadır. Bu özelliği ile bor, bitkinin büyüme ve verimi üzerinde ve besin elementi alımında belirleyici bir role sahiptir. Bitkilerin hücre duvarlarında pektin maddesine bağlı olarak bulunan bor, hücre duvarlarına önemli bir sağlamlık ve bütünlük kazandırmaktadır. Böylece bor bitki dokularını, patojen girişine ve enfeksiyona karşı koruyucu bir rol üstlenmekte ve bitkilerin hastalıklara karşı direncini arttıran önemli bir besin elementi olarak karşımıza çıkmaktadır. Borun en dikkat çekici işlevlerinden birisi de, polen oluşumu /tozlaşma, döllenme ve meyve tutumundaki rolüdür. Çoğunlukla, bor noksanlığı çeken bitkilerde vejetatif büyüme etkilenmezken, generatif büyümede ve meyve oluşumunda ciddi azalmalar ortaya çıkar. Bor bitki içinde floem iletim demetinde zor taşınan bir element olarak bilinir ve noksanlık belirtileri genç yapraklarda ve sürgünlerde ortaya çıkar. Bu yüzden, özellikle çiçeklenme ve meyve/tane oluşum döneminde yapraklardan bitkilere kontrollü bir bor gübrelemesinin yapılması yüksek verim için bir verimi garanti etmek adına önemlidir. Bor noksanlığı problemi, topraklarda veya yapraklarda borun yeterli olması durumunda dahi ortaya çıkabilir. Bu durum, daha çok hava neminin yüksek ve transpirasyonun düşük olduğu koşullarda belirgin biçimde ortaya çıkar. Hücre duvarı kompozisyonu ve pektin maddesi miktarına bağlı olmak üzere bitkilerin bor gereksinimi türden türe önemli farklılıklar göstermektedir. Genelde, tahıllar gibi bor gereksinimi düşük olan bitkilere 100 -200 g/da bor önerilirken; bu oran, şeker pancarı, kolza, ayçiçeği gibi bora gereksinimi yüksek olan bitkilerde 400 g’a çıkabilmektedir. Yapraktan yapılacak bor gübrelemesinde ise genelde kabul gören oran 250-300 mg B/litre olacak şekilde önerilmektedir. 

Anahtar Kelimeler

• Bor,borlu gübreler,borlu gübreleme

The importance of boron for plants

Öz

In plants, boron deficiency occurs most often in acidic sandy soils with low organic matter, high leaching capacity, and frequent lime applications. In addition, boron deficiency is also observed in clayey and high pH soil with high boron adsorption/fixation capacity. Under boron deficiency conditions, the formation, structural stability and functional integrity of cell walls are damaged. Up to 90% of boron in plants is located on cell walls as a structural element and contributes to maintenance of the stability of biological membranes. With these functions boron plays decisive roles in plant growth, yield and nutrient uptake. Boron, as a cell wall element is associated with the pectin substance and provides a substantial strength and stability to cell walls. Thanks to these functions, boron plays a protective role against the penetration and infection of pathogens into plant tissues and increases high resistance of plants to diseases. One of the most particular functions of boron in plants is its role in pollination, fertilization and fruit setting. Therefore, in most cases, vegetative growth is not affected in plants by boron deficiency, while generative growth and fruit formation are affected seriously. Among plant mineral nutrients, boron show the lowest phloem mobility. For this reason, foliar boron fertilization based on leaf analysis is of great importance, especially during the periods of flowering and fruit/seed formation to ensure high yields. Boron deficiency problem can even occur in plants despite of sufficiently high amounts of boron in soils or in fully-expanded leaves which is usually common under conditions where the humidity is high and the transpiration is low. Boron requirements of plants varies considerably from species to species depending on the composition of the cell wall and the amount of pectin. Thus, it is very important to take into account plant species when boron fertilizers are applied. In general, 1 to 2 kg/ha of boron is recommended for plants with low boron requirements, such as cereals, and this rate can be 4 kg for plants with high boron requirement such as sugar beet, rape and sunflower. In the case of foliar boron fertilization, 250-300 mg B/liter is most commonly recommended rate. 

Anahtar Kelimeler

• Boron,boron fertilizers,fertilization with boron

Kaynakça

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