Role of endogenous gibberellins in germination of melon (Cucumis melo) seeds

Abstract

The effect of the plant growth retardants ancymidol. mefluidide and uniconazole on germination of two melon accessions differing in their ability to germinate at 14°C was examined. The accessions were the cold sensitive Noy Yizre'el and the cold tolerant Persia 202. The three growth retardants were able to delay the germination of intact Noy Yizre'el seeds, but did not affect that of intact Persia 202 seeds. On the other hand germination of decoated seeds of both accessions was unaffected by these inhibitors at normal oxygen concentration, but was inhibited at 5% oxygen. When gibberellin‐like activity was measured by a dwarf rice biological assay following HPLC fractionation, it was found that seeds of Persia 202 contained much more gibberellin‐like activity than Noy Yizre'el seeds. Among the extracted compounds several endogenous gibberellins were identified by combined gas chromatography‐mass spectrometry (GC‐MS). They included GA4, GA20, GA1 and GA3 in Noy Yizre'el and GA34, GA20, GA1 and GA8 in Persia 202. It is suggested that the better germination of intact Persia 202 seeds, compared to Noy Yizre'el seeds at low temperature and low oxygen concentration, is due to a higher endogenous level of GA and a better seed coat permeability to oxygen.

Low-temperature Germination of Melons Is Affected by Seedcoat Characteristics and Embryo Genotype

“…These data revealed that all seed generations in the present study were vigorous seeds and germinated well, whereas the germination rate was affected by seedcoat characters and not only by the embryo genotype (Edelstein and Kigel, 1990). P202 and P202 · NY have the same seedcoat characterized by intercellular spaces in the outer layers (Edelstein et al, 1995a) (Fig. 1) and lower MDG values than NY and NY · P202.…”

“…Germination percentages and rates in F 1 , F 2 , and BC 1 families show low-temperature germination depends both on seedcoat characters and on genotype. Relatively high germination percentages in all generations as compared with NY can be attributed to dominant gene(s) in P202 for low-temperature germination and perhaps to higher gibberellin content and metabolic activity compared with NY seeds (Edelstein et al, 1995a(Edelstein et al, , 2001. Furthermore, the significant differences in germination percentages in the four BC 1 families between those with three to four P202 and three to four NY genotypes when all of them have the same seedcoat genotype supports this idea.…”

“…Pregermi-nation treatments like exogenous application of PGR or osmoconditioning are effective tools in improving melon seed germination (Nelson and Sharples, 1980;Nerson and Govers, 1986). Later studies revealed that the ability of the birdsnest line P202 to germinate at low temperature was accompanied by a relatively high endogenous gibberellin content (Edelstein et al, 1995a) and high metabolic activity (Edelstein et al, 2001).…”

Cucurbit Seed Development and Production

“…Also, im- mature muskmelon seeds are the most sensitive to exogenous ABA early in development when ABA levels were highest in the tissue (Welbaum et al, 1990). Higher levels of endogenous gibberellic acid-like substances in muskmelon embryos were correlated with superior germination under suboptimal conditions, indicating that gibberellic acid (GA) may play an important role in muskmelon seed germination (Edelstein et al, 1995a). Gibberellic acid levels were not measured in developing seeds in this study.…”

Controlling Plug Height of Verbena, Celosia, and Pansy by Treating Seeds with Paclobutrazol

“…Seedcoats represent a barrier for some growth regulators (Pressman and Shaked, 1988). High seed GA content made growth regulators ineffective in inhibiting germination regardless of the presence of seedcoats (Edelstein et al, 1995). We can speculate that GA was already synthesized in celosia seeds by the time of paclobutrazol applications.…”