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Changes in Δ 5 ‐ and Δ 7 ‐sterols during germination and seedling development of Cucurbita maxima during germination and seedling development of Cucurbita maxima
Author(s) -
Garg Vipin K.,
Nes William R.
Publication year - 1985
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02534771
Subject(s) - cucurbita maxima , seedling , germination , sterol , botany , biology , biochemistry , cholesterol
While seeds of Cucurbita maxima contain both Δ 5 ‐ and Δ 7 ‐sterols, the former, which have been described earlier, now have been found to disappear during germination. This suggests that a function exists for the Δ 5 ‐compounds only in the early part of the life cycle of C. maxima , unlike most of the other higher plants studied. In contrast to the Δ 5 ‐sterols, the level of Δ 7 ‐sterols increased during germination as well as during seedling development and maturation. The period of transition between germination and seedling development appeared to be of special importance in terms of sterol changes. This period represented a surge of sterol biosynthesis with an ontogenetic shift in sterol composition from approximately equal amounts of 24α‐ and 24β‐ethyl stereochemistry to a predominance of the former. The sterol composition of the mature plants included only about 5% of the 24β‐ethylsterols. The configurational relationships were demonstrated by high resolution 1 H‐NMR. The sterols of the mature plants were: 25(27)‐dehydrochondrillasterol, 24β‐ethyl‐25(27)‐dehydrolathosterol, avenasterol, spinasterol, 22‐dihydrospinasterol and 24ξ‐methyllathosterol. Based on the changes which occurred in the relative amounts of the Δ 7 ‐sterols, it did not appear that the Δ 5 ‐components were being converted to their Δ 7 ‐analogs.