RNA and protein synthesis; prerequisites of red light-induced gibberellin synthesis

Effect of light and gibberellic acid on coleoptile and first-foliage-leaf growth in durum wheat (Triticum durum Desf.)

A comparison has been made of the relative effectiveness of light quality and quantity and gibberellic acid (GA3) treatment on the elongation growth of the coleoptile and the first foliage leaf in durum wheat (Triticum durum Desf. cvs. Cappelli and Creso). The cultivar Creso is a shortstrawed variety carrying the Gai 1 gene on chromosome 4A, which influences both plant height and insensitivity to applied gibberellins. The main conclusions are as follows: 1) coleoptile elongation growth appears to be modulated via the fluencerate-dependent action of a blue-light receptor and via a low energy response of phytochrome; 2) the inhibition of first-foliage-leaf growth depends on the operation of a single blue-light-responsive photoreceptor; 3) high energy blue light produces the same inhibitory effect on the two wheat cultivars, whereas at relatively low fluences of white and blue light, the cultivar Creso is more sensitive; 4) the insensitivity to applied GA3 exerted by the gene Gai 1 in Creso is independent of light; 5) in Cappelli, the action of light on coleoptiles appears to be independent of the applied GA3, whereas the hormone is able to change the pattern of growth inhibition of the first-foliage-leaf.

Red light induced production of gibberellin-like substances in homogenates of etiolated wheat leaves and in suspensions of intact etioplasts

Homogenates of etiolated wheat leaves contain increased levels of acidic gibberellin (GA)-like substances following treatment with red light. Differential centrifugation of homogenates indicates that the response is confined to the 1000 g (or plastid) fraction. Irradiation of suspensions of intact etioplasts also increases the level of extractable GA-like activity. Phytochrome can be detected spectrophotometrically in preparations of etioplasts. The response in etioplasts can be inhibited by chloramphenicol, but not by cycloheximide, and partially by Amo 1618. The GA-like substances produced in etioplasts seem capable of passing into the surrounding medium within 20 min.

Photocontrol of gibberellin levels as related to the unrolling of etiolated wheat leaves

The rapid increase in acidic gibberellin-like (GA-like) activity occurring in etiolated wheat (Triticum aestivum L.); leaf tissue in response to red light is phytochrome controlled. The production of some of the GA-like activity appears to possess a similar escapetime from far-red reversibility to leaf unrolling and is sensitive to Amo 1618. Application of these GA-like substances to leaf sections maintained in the dark causes unrolling. Increased GA-like activity can also be detected in non-irradiated portions of partly irradiated leaves.

Red-light-enhanced conversion of tritiated gibberellin A9 into other gibberellin-like substances in homogenates of etiolated barley leaves

Irradiation of homogenates of etiolated barley leaves with red light resulted in an increase in the levels of gibberellin (GA)-like substances as compared to dark controls. When homogenates were fed with [(3)H]-GA9 there was as incorporation of the radioactivity into a number of other GA's: this process occurred to a greater extent in red light than in darkness, and could be inhibited by boiling the extract prior to addition of the [(3)H]-GA9.

The red light controlled production of gibberellin in etiolated wheat leaves

Most of the gibberellin activity detectable in extracts of etiolated wheat leaf tissue occurs in a bound form. There is a rapid increase in extractable gibberellin-like substances following exposure of the tissue to red light with a concomitant fall in the amount of bound gibberellin. Actinomycin-D and AMo 1618 do not inhibit this initial phase of red light stimulated gibberellin production.It is concluded that red light stimulated gibberellin production in etiolated wheat leaf tissue is due to release from a bound form and to synthesis.