PENGARUH TIMBAL DAN KADMIUM TERHADAP PERTUMBUHAN TANAMAN KEDELAI GLYCINE MAX (L.) MERR. )
A B S T R A K
Telah diteliti pengaruh timbal (Pb) dan kadmium (Cd) terhadap pertumbuhan tanaman kedelai ( Glycine max
(1.)
Merr.) dengan kultur hidroponik. Hasil penelitian menunjukkan bahwa Pb dan Cd yang masing-masing diberikan berupa larutan PbEDTA dan CdC12 , di dalam larutan nutrisi Rorison dapat menimbulkan gejala keracunan pada tanaman kedelai umur 17 hari. Gejala keracunan Pb tampak pada daun muda
yang mengalami klorosis di antara urat daun. Perlakuan dengan Pb masing-masing 45 dan 85 ppm selama 18 hari menye babkan keracunan dan sangat nyata mempengaruhi penurunan berat kering akar dan konsentrasi klorofil a daun. Keha diran Pb 100 dan 300 ppm menurunkan persentase perkecam bahan biji di dalam cawan Petri, menghambat pertumbuhan akar sekunder serta menimbulkan klorosis pada daun unifo lium kecambah. Kedelai yang keracunan Cd berwarna merah kecoklatan pada batang, tangkai dan urat daun, daun keri ting dan berorientasi vertikal, sudut daun mengecil, pucuk dan daun muda mengalami klorosis serta tanaman kerdil. Lo-
gam Cd sebanyak 0,9 ppm menimbulkan keracunan pada tanaman muda, sangat nyata menghambat penambahan tinggi, menurun kan berat kering tanaman serta mengurangi konsentrasi klorofil daun muda. Logam Cd 1,0 dan 9,0 ppm tidak menurunkan persentase perkecambahan biji yang berarti tetapi nyata mengganggu pemanjangan epikotil dan pertumbuhan akar ke cambah. Walaupun Pb dan Cd dapat diakumulasi di pucuk ke cambah, tetapi pemanjangan hipokotil dan biomasa pucuk ti-
dak terpengaruh. Kehadiran Pb berlebih di dalam larutan nutrisi dapat mengubah akumulasi Mg dan Fe tanaman, se dangkan logam Cd mengubah akumulasi Ca, Mg, Fe dan Mn ta naman muda. Di dalam penelitian ini, tingkat keracunan gangguan pertumbuhan, penurunan biomasa dan besarnya akumulasi Cd atau Pb ini berkorelasi positif dengan konsen trasi ke dua logam berat tersebut.
A B S T R A C T
THE EFFECT OF LEAD AND CADMIUM ON THE GROWTH OF SOYBEAN
(GLYCINE MAX (L.) MERR.) PLANTS
The effect of lead (Pb) and cadmium (Cd) treatment on vegetative growth of soybean (Glycine max (L.) Merr.) has been investigated using hydroponic culture. The results of this study demonstrate that Pb and Cd which were supplied in Rorison's solutions as PbEDTA and CdC12, respectively, induced
toxicity
symptoms
on
17-day-old
soybeans.
Lead
toxicity symptom appeared as interveinal chlorosis on the young leaves. Plants growing in solutions that received 45 or 85 ppm Pb during 18 days exhibited intoxication, and highly significant reduced root dry weight and leaf chlorophyll a content. In the presence of 100 and 300 ppm Pb on Petri
dish,
soybean
seeds
showed
a.reduction
in
the
percentage of germination. The same concentrations inhibited the secondary root development of the seedlings and chlorosis
was
found
on
the
unifoliolate
leaves.
Cadmium
toxicity symptoms appeared as reddish-brown spots on stem, petiole and along the veins of leaves, the leaves curled and
vertically
oriented,
with
reduced
leaf
angles,
the
shoot and young trifoliolate leaves became chlorotic and the plants were stunted. Cadmium treatment at 0.90 ppm caused intoxication of young soybean plants, gave a highly significant reduced plant height, plant dry weight and the chlorophyll content of young leaves. The percentage
of
germination of seeds was slightly reduced by Cd treatment at 1.0 and 9.0 ppm, but significantly inhibited epicotyl and seedling root development. Although Pb and Cd were accumulated in the shoot of seedling, the growth of hypocotyl and shoot biomass were not affected. Changes in accumulation of Mg and Fe in plants grown in the presence of excess Pb were observed, while Cd influenced the accumulation of Ca,Mg,Fe and Mn in treated plants. Lead and Cd accumulation in the root were always higher than in the shoot. In this investigation, toxicity level, growth dis turbance, biomass reduction and accumulation of cadmium or lead were positively correlated with concentration of respective metal.
