The Effect of Light Quality and Intensity on Sexual Expression in Equisetum Gametophytes

Abstract

A series of experiments to determine the effect of light quality and light intensity on sexual expression in Equisetum gametophytes showed that one species, E. arvense, is strongly affected by light intensity; another species, E. hyemale, is strongly affected by light quality; and a third species, E. fluviatile, is relatively unaffected by either light quality or light intensity. Supplementation of mineral media with sucrose indicates that this light effect is not photosynthetic, and in fact suggests that sucrose itself has a morphogenetic effect on sexual determination in Equisetum gametophytes.

Towards an understanding of sex determination in Equisetum: an analysis of regeneration in gametophytes of the subgenus Equisetum

“…These observations on gametophyte sexual behaviour open the way to a critical experimental investigation of the mechanism of sex determination. Whereas previous researchers (for reviews see Duckett, 1970aDuckett, , 1972Hauke, 1971;Mohan Ram & Chatterjee, 1970) have concentrated on the effects of different environmental factors such as light, composition of the culture medium and crowding on the sexuality of young sametophytes, here the mechanism of sex determination is analysed in the light of subculturing experiments on various parts of sexually mature gametophytes under the same, carefully defined, conditions. The reason for this approach is that, in contrast to homosporous ferns (Miller, 1968), sex determination and gametophyte growth in Equisetum are intimately interrelated.…”

Environmental Sex Determination in the Genus Equisetum: Sugars Induce Male Sex Expression in Cultured Gametophytes

“…3 imize sex-biased mortality or inhibition as a possible cause of variation in the analyzed sex ratios. The absence of such care, as well as differences in culture conditions, such as light level, light quality, and basic growth medium (Mohan Ram and Chatterjee 1970;Hauke 1971Hauke , 1977, may account for the discrepancies found across previous results. In addition, the statistical analyses used in some of these investigations might have confounded the growth-medium effect with the effect of crowding, a factor that itself seems able to modify the sex ratio of cultured Equisetum gametophytes (Hauke 1977).…”

“…The sexual determination of Equisetum gametophytes has been problematic for many years, with various authors emphasizing genetic sex determination, environmental sex determination, or a mixture of both (Mohan Ram and Chatterjee 1970;Laroche et al 1972Laroche et al , 1978Hauke 1977). However, the observations that (i) archegonial (female) gametophytes always change to antheridial (male) lobe production when cultured over a prolonged time, (ii) secondary archegonial branches can be regenerated from otherwise purely male gametophytes, and (iii) the proportions of male and female gametophytes developing from the same initial set of spores are highly sensitive to growth conditions all indicate that the spores of Equisetum are not individually predetermined for the expression of one sex or the other (Duckett 1970(Duckett , 1972(Duckett , 1977(Duckett , 1979.…”

“…To better understand sex determination in Equisetum gametophytes, several authors have studied their response to a number of culture conditions in vitro (Mohan Ram and Chatterjee 1970;Hauke 1971Hauke , 1977. Studied environmental factors include light quality and level, crowding, pH, and sucrose concentration in the culture media.…”

“…For example, sucrose enrichment has been reported (i) to inhibit female sex differentiation in Equisetum ramosissimum (Mohan Ram and Chatterjee 1970), (ii) to decrease the proportion of males in Equisetum arvense (Hauke 1971(Hauke , 1977, (iii) to increase the proportion of males in E. ramosissimum (Mohan Ram and Chatterjee 1970) and Equisetum hyemale (Hauke 1971), or (iv) to have no effect on sex expression in the same E. hyemale (Hauke 1977). Hauke (1977) concluded: "A number of experiments utilizing sugar enrichment were attempted, but the results were so inconsistent that no conclusions can be drawn from them" (p. 29). Such discrepancies may be explained by variations in culture conditions between experiments, leading to the interaction of other important factors such as light quality and crowding.…”