Germination of Cocklebur Seeds: Interactions Between Gibberellic Acid, Benzyladenine, Thiourea, KNO3 and Gaseous Factors

Abstract

The germination response of small, upper seeds of cocklebur (Xanthium pensylvanicum Wallr.) was examined with respect to the germination stimulants oxygen, CO2, ethylene, gibberellic acid, benzyladenine, thiourea and KNO3. Thiourea, benzyladenine, ethylene and oxygen-enriched air (50% O2) stimulated germination, but gibberellic acid was only slightly effective and KNO3 had little effect. In contact with thiourea or CO2, seeds usually germinated by extrusion of the radicle without any change of germination pattern, but while in O2-enriched air the seed coat was predominantly ruptured at the cotyledon end. In about half of the seeds germinated with ethylene, benzyladenine and gibberellic acid, the seed coat split at the cotyledon side. Trapping of endogenously evolved ethylene and CO2 from the ambient atmosphere did not affect the actions of benzyladenine and gibberellic acid, but the action of thiourea was significantly reduced by trapping CO2. Except for thiourea, with which the CO2 production was enhanced, benzyladenine, gibberellic acid and KNO3 did not increase CO2 and ethylene production from the seed in the germination period. The maximum germination percentage was obtained by a combi- nation of CO2, ethylene, gibberellic acid and benzyladenine, but the interaction of gibberellic acid and benzyladenine was not significant. In contrast, the interaction of gibberellic acid and ethylene was very effective, and further addition of CO2 to this combination hastened the germination in air and also facilitated it under the semi-anaerobiosis assumed to exist in a natural underground habitat, although the effect of benzyladenine alone was nearly completely suppressed by semi- anaerobiosis. Thus the particular importance of CO2, ethylene and gibberellic acid in the normal germination regulation of this seed is suggested.

Note on the germination of Vochysia tucanorum seeds treated with growth regulators

“…The germination of seeds treated with CEPA was also advanced compared to the distilled water control, although to a lesser extent than that for the mixture CEPA + GA 3 . These results suggest an interaction of ethylene and gibberellins in improving the germination rate of Vochysia tucanorum seeds, as reported for Xanthium strumarium L. (Esashi et al 1975) and Rumex crispus L. (Samimy & Khan 1983). The soaking of V. tucanorum seeds in GA 3 only had no effect on germination after 7 days (table 1).…”

Implication of Ethylene in the Release of Secondary Dormancy in Amaranthus caudatus L. Seeds by Gibberellins or Cytokinin

“…All of our results indicate that to observe the maximum effect, or to accelerate the effect of GA or BA, the presence of exogenous ethylene is required. An additive or synergistic effect of ethylene and gibberellins in breaking seed dormancy was also demonstrated in Rumex crispus (Samimy and Khan 1983), Xanthium strumarium (Esashi et al 1975), and lettuce (Keys et al 1975).…”

Ethylene, a key factor in the regulation of seed dormancy

“…Both hormones promote the germination of primary dormant seeds of Arabidopsis ( Ogawa et al, 2003 ; Siriwitayawan et al, 2003 ), Amaranthus retroflexus ( Kepczynski et al, 1996b ; Kepczynski and Sznigir, 2014 ), beechnut ( Calvo et al, 2004a , b ), apple ( Kepczynski et al, 1977 ; Sinska and Gladon, 1984 ; Sinska, 1989 ; Lewak, 2011 ), and Sisymbrium officinale ( Iglesias-Fernandez and Matilla, 2010 ). They also break secondary dormancy in Rumex crispus ( Samimy and Khan, 1983 ) and cocklebur seeds ( Esashi et al, 1975 ), and thermodormancy in lettuce achenes ( Keys et al, 1975 ). In Arabidopsis , C 2 H 4 restores the germination of the GA-deficient mutant ga1-3 ( Karssen et al, 1989 ), and GA 3 stimulates that of the etr1 mutant ( Bleecker et al, 1988 ), while no stimulatory effect is noted on the germination of the GA-deficient gib-1 mutant in tomato ( Groot and Karssen, 1987 ).…”