Faruk Ozkutlu

Shoot biomass and zinc/cadmium uptake for hyperaccumulator and non-accumulator Thlaspi species in response to growth on a zinc-deficient calcareous soil

Thlaspi caerulescens is one of the best-known heavy metal hyperaccumulating plant species. It exhibits the ability to extract metals from soils and accumulates them in shoots at extremely high concentrations, particularly zinc (Zn) and cadmium (Cd). Using T. caerulescens (J. and C. Presl, ecotype Prayon) and a closely related non-accumulator species T. arvense, greenhouse experiments were carried out to study shoot growth (dry matter production) and Zn and Cd uptake from a severely Zn-deficient calcareous soil (DTPA-Zn: 0.09 mg kg−1 soil) supplemented with increasing amounts of Zn (0, 0.05, 0.5, 5, 25 and 75 mg kg−1 soil) and Cd (0 and 25 mg kg−1 soil). Shoot dry matter production of T. caerulescens was severely depressed by Zn deficiency, while in T. arvense, Zn deficiency slightly reduced growth. At the lowest Zn supplies (0 and 0.05 mg Zn kg−1 soil), T. caerulescens showed very severe Zn deficiency symptoms, including decreased leaf size and development of chlorosis and whitish-brown necrosis on the younger leaves. These symptoms were slight in T. arvense. At the highest Zn supply, leaves of T. caerulescens did not show any symptoms, but in T. arvense there were some necrotic patches on the margins of older leaves, probably due to Zn toxicity. With increasing Zn supply from 0 to 75 mg kg−1 soil, shoot dry matter production was increased by 4-fold in T. caerulescens and only 1.3-fold in T. arvense. Supply of Cd resulted in marked decrease in shoot growth of T. arvense, particularly under low Zn supply, but had no effect on the growth of T. caerulescens. At the low soil Zn levels ( 5 mg Zn kg−1), shoot Zn concentrations were considerably higher in T. caerulescens than T. arvense. Increase in Zn supply from 0 to 75 mg kg−1 enhanced shoot Zn concentrations by 84-fold in T. caerulescens and only 8-fold in T. arvense. Shoot Zn concentrations of both species were not affected by Cd supply, while increase in Zn supply did not affect Cd concentrations in shoot of T. caerulescens, but markedly reduced them in T. arvense. The results demonstrate that T. caerulescens is extremely sensitive to Zn deficiency in soils, but tolerant to excessive accumulation of Zn and also Cd in shoot, while T. arvense is tolerant to Zn deficiency but not to accumulation of Zn and Cd in shoot. Hyperaccumulation of Zn in T. caerulescens possibly depends on the existence of high concentrations of plant-available Zn in soils, which suggests that root-based mechanisms associated with increasing metal availability in the rhizosphere (e.g., rhizosphere acidification or release of Zn-mobilizing organic compounds from roots) only play a minor role in metal hyperaccumulation by T. caerulescens. The findings also suggest that the processes causing the metal hyperaccumulation trait in T. caerulescens also cause this plant species to be sensitive to Zn deficiency stress.

Effect of Zinc Humate on Growth of Soybean and Wheat in Zinc‐Deficient Calcareous Soil

Abstract Humic acids have many benefits for plant growth and development, and these effects may be maximized if these materials are combined with micronutrient applications. In the present study, pot experiments were conducted to evaluate the effects of zinc (Zn) humate and ZnSO4 on growth of wheat and soybean in a severely Zn‐deficient calcareous soil (DTPA‐Zn: 0.10 mg kg−1 soil). Plants were grown for 24 (wheat) and 28 days (soybean) with 0 or 5 mg kg−1 of Zn as either ZnSO4 or Zn humate. Zinc humate used in the experiments was obtained from Humintech GmbH, Germany, and contained 5% of Zn. When Zn was not supplied, plants rapidly developed visible symptoms of Zn deficiency (e.g., chlorosis and brown patches on young leaves in soybean and necrotic patches on middle‐aged leaves in wheat). Adding Zn humate eliminated Zn‐deficiency symptoms and enhanced dry matter production by 50% in soybean and 120% in wheat. Zinc‐humate and ZnSO4 were similarly effective in increasing dry matter production in wheat; but Zn humate increased soybean dry matter more than ZnSO4. When Zn was not supplied, Zn concentrations were 6 mg kg−1 for wheat and 8 mg kg−1 for soybean. Application of Zn humate and ZnSO4 increased shoot Zn concentration of plants to 36 and 34 mg kg−1 in wheat and to 13 and 18 mg kg−1 in soybean, respectively. The results indicate that soybean and wheat plants can efficiently utilize Zn chelated to humic acid in calcareous soils, and this utilization is comparable to the utilization of Zn from ZnSO4. Under Zn‐deficient soil conditions, plant growth and yield can be maximized by the combined positive effects of Zn and humic acids.

Çilekte bor gübrelemesinin bozuk şekilli meyve oluşumunun önlenmesi ve yaprak mineral içerikleri üzerine etkisi

Bor (B) bitkilerin buyume ve gelismeleri icin gerekli mikroelementtir. Borun bitkideki noksanlik ve fazlalik araliklari birbirine cok yakindir. Bor gubrelemesinde bitkinin istegi dikkate alinmalidir. Cileklerde bozuk sekilli meyve olusumlari bircok faktorle iliskilidir. Bozuk sekilli meyve olusumunun yetersiz tozlanma ve dollenmeden kaynaklandigi ve bu durumun bor beslenmesiyle iliskili oldugu bilinmektedir. Genellikle cilek uretiminde bitkiler tam beslenemediginde elde edilen meyvelerin bir bolumunun bozuk sekilli elde edilmesi ekonomik kayiplara neden olmaktadir. Ozellikle cilek bitkisinde B gubre uygulamalariyla meyve kalitesinin artirilmasi mumkundur. Bu arastirmada sera kosullarinda B noksan bir toprak kullanilarak topraktan artan dozlarda (0, 2.5, 5.0, 10.0 mg B kg-1) bor gubrelemesinin Camarosa ve Sweet Charlie cilek cesitlerinin bozuk sekilli meyve olusumlari, yaprak mineral element konsantrasyonu ve verim uzerine etkileri belirlenmistir. Hic B gubrelemesi yapilmayan kontrol bitkilerinde bozuk sekilli meyvelerin olustugu ve ekonomik kayiplarin oldugu tespit edilmistir. Dusuk doz (2,5 mg B kg-1 toprak) B gubrelemesinin bozuk sekilli meyve olusumunu azalttigi, yuksek doz (10,0 mg B kg-1 toprak) B gubrelemesinin toksik etki ettigi ve olusan meyvelerin kucuk ve meyve agirliginin dusuk oldugu bulunmustur. Ayrica, dusuk doz (2,5 mg B kg-1 toprak) B gubrelemesinin cilek yapraklarinin toplam Azot (N) ve kalsiyum (Ca) miktarinda azalmaya neden olmasina karsin fosfor (P), potasyum (K), mangan (Mn), cinko (Zn) ve bakir (Cu) konsatrasyonunu arttirdigi saptanmistir. Bu arastirmadan elde edilen sonuclara gore, B bakimindan yetersiz olan topraklarda dusuk miktarda B gubrelemesiyle cilek meyvesinde bozuk sekilli olusumlarin azaltilarak ekonomik kayiplarin minimize edilmesi ve meyve kalitesinin arttirilmasinin mumkun olabilecegi ortaya konmustur.