Lettuce (Lactuca sativa L.) seed germination at high temperature (35oC) and the
relationship to endo--mannanase activity (EC 3.2.1.78) and the endosperm tissue composition
were investigated. Significant differences in sugar make-up in both the micropylar and the lateral
regions of the endosperm were observed among the genotypes Dark Green Boston (DGB),
Everglades (EVE) and PI 251245 (PI). A higher amount of total sugars was observed in the
micropylar region when compared to the lateral region of the endosperm. Thermosensitive DGB
had more galactose and mannose in the micropylar region as compared to thermotolerant EVE
and PI. Seeds from thermotolerant genotypes had higher endo--mannanase activity prior to radicle
protrusion at 35oC than did the thermosensitive genotype. A relationship between seed germination
at high temperature and an increase in endo-R-mannanase activity before radicle protrusion was
observed.