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Quantal Response of Seed Germination in Seven Genera of Cruciferae to White Light of Varying Photon Flux Density and Photoperiod

1989; Oxford University Press; Volume: 63; Issue: 1 Linguagem: Inglês

10.1093/oxfordjournals.aob.a087717

1095-8290

R. H. Ellis, T. D. HONG, Ε. H. Roberts,

Seed Germination and Physiology

The response of the germination of seeds of Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L., Nasturtium officinale R. Br., and Rorippa palustris (L.) Besser to white fluorescent light of different photon flux densities applied for different daily durations in a diurnal alternating temperature regime of 20 °C/30 °C (16 h/8 h) was quantified by linear relations between probit percentage germination and the logarithm of photon dose, the product of photon flux density and duration. The low energy reaction, in which increasing dose promotes germination, was detected in all the seed populations but in Barbarea vema and Brassica Juncea the lowest photon dose applied (10−5−2 and 10−5 7 mol m−2 d−1, respectively) was sufficient to saturate the response. Comparisons, where possible, between photoperiods demonstrated reciprocity, i.e. germination was proportional to photon dose irrespective of photoperiod, for the low energy reaction in Brassica oleracea (1 min d−1 to 1 h d−1), Camelina saliva (1 min d−1 to 8 h d−1), Eruca saliva (1 min d−1 to 24 h d−1), Lepidium sativum (I min d−1 to 8 h d−1) and Rorippa palustris (1 min d−1 to 8 h d−1), but not in Brassica chinensis and Nasturtium officinale. The high irradiance reaction, in which increasing dose inhibits germination, was detected in Barbarea vema, Brassica chinensis, Brassica juncea, Brassica oleracea, and Camelina saliva. The minimum dose at which inhibition was detected was lO−0−3 mol m−2 d−1. These results are discussed in the context of devising optimal light regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantified with 3 × 10−4 M GA2, co-applied (Brassica chinensis, Camelina saliva, and Lepidium sativum) and with 2 × 10−2 M potassium nitrate co-applied (Brassica chinensis). In the latter case potassium nitrate had no effect in the dark and inhibited germination in the light, but GA2, promoted germination substantially in all three species. Variation amongst seeds in the minimum photon dose required to stimulate germination was not affected by co-application of GA2, in Brassica chinensis and Camelina saliva, whereas seeds of Lepidium salivum showed a narrower distribution of sensitivities to the low energy reaction in the presence of GA2