شیب پخش در غشای نازک (DGT) تکنیکی جدید در اندازه‌گیری زیست فراهمی عناصر معدنی خاک برای گیاهان

نوع مقاله: علمی ترویجی

نویسندگان

1 دانشیار گروه علوم خاک،دانشکده کشاورزی دانشگاه تبریز.

2 دانشجوی دکتری،شیمی و حاصلخیزی خاک،گروه علوم خاک،دانشکده کشاورزی دانشگاه تبریز.

چکیده

مقدار کل عناصر معدنی در خاک ارتباط بسیار ضعیفی با فراهمی عناصر برای گیاهان دارد. تکنیک DGT (شیب پخش در غشای نازک) اخیراً در پیش­بینی زیست فراهمی عناصر کمیاب و کم مصرف، فسفر و پتاسیم عملکرد خوبی از خود نشان داده است. در این تکنیک، عناصر پس از عبور از لایه هیدروژل در ژل پیوندی تجمع می­یابند. در این مقاله مروری، جزئیات ساخت و استفاده از DGT، شرایطی که در آن همبستگی DGT با پاسخ­های گیاهی قابل توجه است، بحث می­شود. تئوری روش DGT تشریح شده و به برخی نتایج حاصله در مورد عناصر کمیاب، فسفر و پتاسیم اشاره خواهد شد. اگر جریان پخشیدگی عنصر مورد نظر از خاک به ریشه­های گیاهی محدود کننده سرعت جذب باشد، همبستگی قوی بین DGT و جذب گیاهی قابل پیش­بینی است. اگر جذب توسط جریان پخشیدگی محدودکننده نشود، ممکن است شارش DGT و جذب گیاهی همبستگی نشان دهد به شرطی که جذب گیاهی هنوز اشباع نشده باشد. اما رقابت کاتیون­ها ممکن است بر جذب عناصر توسط گیاهان تحت این شرایط تاثیرگذار باشد، در حالی­که بر شارش DGT اثری ندارند. همچنین اگر پخشیدگی محدودکننده نباشد، کمپلکس­های ناپایدار، مشارکتی در جذب عناصر نخواهند داشت اما توسط DGT اندازه­گیری می­شوند. بنابراین اگر جذب گیاهی توسط پخشیدگی محدود نشود، تفسیر همبستگی مشاهده شده با اندازه گیری DGT صحیح نخواهد بود.

کلیدواژه‌ها


عنوان مقاله [English]

Diffusive Gradients in Thin-films (DGT), a New Technique in Predicting Soil Bio-availability of Mineral Elements for Plants

نویسندگان [English]

  • a r 1
  • s h 2
چکیده [English]

Total concentrations of mineral elements in soil bear little relation to their availability for plants. The DGT (diffusive gradients in thin-films) technique has been found to be a good predictor of trace metals, micronutrients, phosphorous and potassium bio-availability and uptake. In the DGT technique, elements are accumulated on a binding gel after their diffusive transport through a hydrogel. In this review paper, we explore in a more detail why and under which conditions DGT correlates with plant uptake. The theoretical considerations will be illustrated and some of  experimental results in relation to metal uptake and toxicity, phosphorus and potassium will be reported. Strong correlations between DGT and plant uptake are predicted if the diffusive transport of the element from soil to the plant roots is rate-limiting for its uptake.   If uptake is not limited by diffusive transport, DGT-fluxes and plant uptake may still show correlation. Of course, this will be true in the condition which plant uptake is not saturated. However, competitive cations may affect the plant uptake under these conditions, whereas they have no effect on the DGT flux. Moreover, labile complexes are not expected to contribute to the plant uptake if diffusion is not limited, but they are measured with DGT. Therefore, if plant uptake is not limited by diffusion, interpretation of the observed correlation in terms of the labile species measured by DGT is inappropriate.

کلیدواژه‌ها [English]

  • Bioavailability
  • Diffusive gradient
  • Hydro-gel
  • Flux
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