NITRATE REDUCTION IN COTYLEDONS OF CICER-ARIETINUM L - INVOLVEMENT OFTHE NITRATE AND PHYTOCHROME IN ITS REGULATION

The addition of nitrate to the incubation medium of seeds or excised c otyledons of Cicer arietinum L., treated with red light, elicits a cle ar inhibition of nitrate reductase activity in the cotyledons of intac t seeds and a marked increase in this activity in excised cotyledons. There appears to be a relationship between nitrate metabolism and nitr ate reductase activity since when the levels of enzyme activity were h igher an accumulation of nitrite in the cotyledons occurred. There doe s not appear to be, however, any clear relationship between phytochrom e and nitrate reductase activity: an increase in the photostationary s tate of phytochrome occurs in cotyledons of chick-pea seeds under trea tment with nitrate and red light, while no nitrate reductase activity is elicited.