Journal Article

The second step of the biphasic endosperm cap weakening that mediates tomato (<i>Lycopersicon esculentum</i>) seed germination is under control of ABA

Peter E. Toorop, Adriaan C. van Aelst and Henk W.M. Hilhorst

in Journal of Experimental Botany

Volume 51, issue 349, pages 1371-1379
Published in print August 2000 | ISSN: 0022-0957
Published online August 2000 | e-ISSN: 1460-2431 | DOI:
The second step of the biphasic endosperm cap weakening that mediates tomato (Lycopersicon esculentum) seed germination is under control of ABA

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The role of abscisic acid (ABA) in the weakening of the endosperm cap prior to radicle protrusion in tomato (Lycopersicon esculentum Mill. cv. Moneymaker) seeds was studied. The endosperm cap weakened substantially in both water and ABA during the first 38 h of imbibition. After 38 h the force required for endosperm cap puncturing was arrested at 0.35 N in ABA, whereas in water a further decrease occurred until the radicle protruded. During the first 2 d of imbibition endo‐β‐mannanase activity was correlated with the decrease in required puncture force and with the appearance of ice‐crystal‐induced porosity in the cell walls as observed by scanning electron microscopy. Prolonged incubation in ABA resulted in the loss of endo‐β‐mannanase activity and the loss of ice‐crystal‐induced porosity, but not in a reversion of the required puncture force. ABA also had a distinct but minor effect on the growth potential of the embryo. However, endosperm cap resistance played the limiting role in the completion of germination. It was concluded that (a) endosperm cap weakening is a biphasic process and (b) inhibition of germination by ABA is through the second step in the endosperm cap weakening process.

Keywords: Abscisic acid; cryo‐scanning electron microscopy; endosperm weakening; endo‐β‐mannanase; tomato seed germination.; gib1, gibberellin‐deficient mutant; cryo‐SEM, cryo‐scanning electron microscopy; PEG, polyethylene glycol 6000.

Journal Article.  5158 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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