Effect of Temperature, Oxygen, and Gibberellic Acid on the Development of Photosensitivity in Oldenlandia corymbosa L. Seeds during Their Incubation in Darkness

Abstract

Two successive phases can be distinguished in the development of the responsiveness to light in Oldenlandia corymbosa L. seeds during their incubation in darkness. During phase I, the responsiveness to light increases with time if there is sufficient 02, and the higher the temperature, the faster the increase. This phase is stimulated by gibberellic acid. During the following phase (II), seeds remain responsive to light at 10 or 20°C, but lose their responsiveness at higher temperature (-30°C). This second phase depends on 2: loss of responsiveness is accelerated at lower 02 concentration. Phase II is only slightly affected by gibberellic acid. The results are discussed in terms of variation of phytochrome and of a reaction along the transduction chain initiated by phototransformation of this pigment, which is finally expressed in germination.The main characteristics of germination of Oldenlandia corymbosa L. seeds (tropical Rubiaceae) have been described in previous studies (2,6,7,9 Phytochrome is involved in the photosensitivity of 0. corymbosa seeds, but long exposures to white or red light are necessary to ensure germination (9, 10). Moreover, the action of light depends on temperature conditions of the preceding dark incubation (9, 10). The absolute requirement for light is lost in the presence of GA3 at sufficiently high concentrations (above 0.1 mM) (8).The purpose of the present study is to determine the effect of temperature, 02, and GA3 on the development of the responsiveness to light in these seeds during incubation in the dark. MATERIALS AND METHODSThe present study was carried out with O2-insensitive seeds, harvested from plants selected to produce only this type of seed (2). These plants were grown in the Phytotron at Gif-sur-Yvette (France) under conditions defined previously (6). Each germination experiment consisted of three replicates (Petri dishes), each containing 100 to 200 seeds placed on filter paper over a layer of cotton wool imbibed with deionized H20, or with GA3 (Fluka Chemical Co.) solutions at different concentrations. The results were expressed as mean values ± SE. Each experiment was repeated 2 to 3 times with different batches of seeds. Since the results of the repeated experiments were qualitatively the same, but differed somewhat quantitatively, only representative experiments are reported. Treatments in different 02-rich atmospheres were applied using the device perfected by Come and Tissaoui (4). White light (13 ± 0.5 Wm2) was provided by two 16-W Mazdafluor fluorescent tubes (warm white).Experimental procedure was as follows. Seeds were first incubated in darkness for various times, on water or on GA3, in air or in various 02 concentrations and at different temperatures. Then, they were irradiated for 4 h at 35C in air. After irradiation, they were transferred in darkness, in air, at 37°C, and germination percentages were determined 7 d later. A seed was considered to have germinated when its radicle had pierced the seed coat. RESULTSInfluence of Temperature Before ...

Inhibition of germination of dormant barley (Hordeum vulgare L.) grains by blue light as related to oxygen and hormonal regulation

“…4). Such oxygen-dependent response to light, which was previously reported in negative photoblastic Bromus rubens and Amaranthus caudatus Gutterman et al 1992) and positive photoblastic Oldenlandia corymbosa (Corbineau & Côme 1985) probably explains the role played by the covering structures in the sensitivity of barley grains to light. Using micro-sensor, Hoang et al (2013a) recently demonstrate that O2 tension in the embryo under the seed-covering structures was 15.8% at 15°C, and considering that O2 solubility is higher at 10°C than at 15°C, the inhibitory action of blue light cannot only be explained by the reduced oxygen supply, as isolated embryos easily germinate in blue light in 15% O2 at 10°C (Fig.…”

“…; Gutterman et al . ) and positive photoblastic Oldenlandia corymbosa (Corbineau & Côme ) probably explains the role played by the covering structures in the sensitivity of barley grains to light. Using micro‐sensor, Hoang et al .…”

Echinochloa crus‐galli seed physiological dormancy and germination responses to hypoxic floodwaters

“…It has been reported that low water availability during droughts can affect the perception of light signals by seeds and the recruitment pattern of seedlings once soils return to field capacity (Botto et al ). In contrast, the effects of water excess on light perception and signalling of the environmental cues breaking seed dormancy have not been addressed, even though hypoxia is known to change seed responsiveness to light in upland plants (Corbineau & Côme ; Hoang et al ). Given that correct perception of signals that break dormancy may be essential to avoid underwater germination, the null hypothesis would be that E. crus‐galli seeds are equally able to perceive light and temperature regimes under hypoxic floodwater as under normoxic conditions, typical of drained soils.…”

Quantifying the oxygen sensitivity of seed germination using a population-based threshold model

“…Generally, the sensitivity of seeds to O 2 deprivation decreases with decreasing temperature, because of reduced respiratory activity and the higher solubility of O 2 in water (Côme and Tissaoui, 1973; Corbineau and Côme, 1995). The acquisition of responsiveness to light of Oldenlandia corymbosa seeds during imbibition requires at least 3.5% O 2 (Corbineau and Côme, 1985), while continuous white light reinforces the sensitivity to O 2 deprivation of negatively photosensitive seeds (Corbineau et al , 1992; Gutterman et al , 1992).…”