Germination of Cicer arietinum seeds and thiourea-induced phytotoxicity

Thiourea, hydroxyurea, phenylthiourea, methylurea, methylthiourea, thiosemicarbazide and 2,2-dithiodipyridine affected the germination of Cicer arietinum L. cv. Castellana (chick-pea) seeds. Microscopic observations of the subapical zone of the radicle showed that thiourea induced an increase in cell volume and length when compared with control seeds germinated at 25° or 30°C in water. These results emphasize the importance of the processes controlling solute and water uptake during early germination of chick-pea seeds. In contrast to this stimulation of volume increase, the thiourea-treated seedlings were unable to synthesize chlorophyll when exposed to light. This toxic effect was reduced when thiourea was administered only during the first few hours of germination. Thiourea also caused an increase in the uptake of ³H-thymidine and ¹⁴C-leucine but it decreased their incorporation into DNA and protein, respectively. These results suggest a stimulation of plasmalemma exchange activities, but toxic or inhibitory effects on other metabolic processes necessary for normal development of seedlings.