Kadmiyum iyonlarının tatlı su bitkisi su mercimeği lemna minor' ün büyüme hızına etkisi

The effect of cadmium ions on the growth rate of the freshwater macrophyte duckweed Lemna minor

Abstract

In this study, the effect of Cd(II) on the growth rate of Lemna minor was investigated in an aqueous media with changing initial pH (4.5-8.0), temperature (15-35ºC) and Cd(II) concentration (0.05-20.0 ppm). The frond numbers were determined by time, and the kinetic model of plant growth was derived and fitted to the first order reaction kinetics. The reaction rate constants (k; d-1) were determined for all conditions. Experimental results showed that k decreased in the Cd(II) containing media according to control. But, plant growth was affected positively in 0.05 ppm. For example, k was found to be 0.194 d-1 for 0.05 ppm at pH 5.0, but it was 0.160 d-1 for the control. Additionally, k decreased significantly in lower pH values, but it increased especially in the pH 7.0-8.0 range. The maximum k was obtained at 25ºC for both Cd(II) containing media and control. When the temperature was increased, k started to decrease at the 25- 30ºC range. For example, it was found 0.145 d-1 for 0.1 ppm Cd(II) and 0.160 d-1 for the control at 25ºC, but it decreased to 0.014 d-1 for 0.1 ppm Cd(II), and 0.121 d-1 for the control at 30ºC. The results showed that Cd(II) was very toxic for Lemna and reduced the growth rates.

Özet

Bu çalýþmada, Cd(II) iyonlarýnýn Lemna minor'ün büyüme hýzýna etkisi, sulu ortamda ortamýn deðiþen baþlangýç pH'ý (4,5-8,0), sýcaklýðý (15-35ºC) ve kadmiyum iyonu konsantrasyonunda (0,05-20,0 ppm) araþtýrýlmýþtýr. Frond sayýsý günlük olarak saptanmýþtýr. Bitkinin zamana baðlý frond sayýsý deðiþiminden kinetik model çýkarýlmýþ ve birinci dereceden reaksiyon kinetiðine uyduðu saptanmýþtýr. Tüm çalýþýlan ortam koþullarý için reaksiyon hýz sabitleri (k; d-1) hesaplanmýþtýr. Elde edilen deneysel sonuçlar büyüme hýz sabitlerinin Cd(II) içeren ortamda kontrol örneklerine göre azaldýðýný göstermiþtir. Fakat, 0,05 ppm'de bitki geliþiminin arttýðý bulunmuþtur. Örneðin, 0,05 ppm Cd(II) deriþiminde pH 5,0 de k deðeri 0,194 d-1, kontrol için 0,160 d-1 bulunmuþtur. Bitkinin büyüme hýzý düþük pH'larda önemli ölçüde azalmýþ, fakat yüksek pH'larda özellikle pH 7,0-8,0 aralýðýnda artmýþtýr. Ayrýca, maksimum k deðeri, gerek Cd(II) içeren ortamda gerekse de kontrol ortamýnda 25ºC'de elde edilmiþtir. Sýcaklýk arttýkça k deðerleri 25-30ºC aralýðýnda azalmýþtýr. Örneðin, 0,1 ppm Cd(II) deriþiminde 25ºC'de k deðeri 0,145 d-1, kontrol için 0,160 d-1 olarak bulunurken; bu deðerler 30ºC' da 0,1 ppm için 0,014 d-1'e, kontrol örneði için 0,121 d-1'e düþmüþtür. Elde edilen sonuçlar kadmiyum iyonlarýnýn Lemna minor için çok toksik olduðunu ve bitki büyüme hýzýný düþürdüðünü göstermiþtir.