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Eco-physiological Investigations on the Amphicarpy of Emex spinosa (L.) Campd.

1977; Elsevier BV; Volume: 166; Issue: 3 Linguagem: Inglês

10.1016/s0367-2530(17)32140-0

1618-0585

M. Evenari, A. Kadouri, Yitzchak Gutterman,

Seed Germination and Physiology

Emex spinosa (L.) Campd. var. minor (Polygonaceae) is an annual amphiearpic desert plant with telechoric, aerial and atelechoric subterranean propagules. The aerial propagules are spiny, small and light, the subterranean ones are large, smooth and heavy. One plant carries few subterranean but many aerial propagules. The optimal germination temperature of the intact non leached aerial propagules is 20°C, light inhibits their germination but even at the optimal temperature in darkness germination percentage is very low. Pre-treatment of the aerial propagules by leaching or alternating temperatures during germination increase the germination percentage considerably. The leachate contains germination inhibitors. The germination percentage of the intact subterranean propagules is under all germination conditions tested, much lower than that of their aerial counterparts. The leachate of the subterranean propagules does not contain a germination inhibitor. Cutting open the aerial or subterranean propagules at their micropylar tip, opening the perianth and the coat of the achene brings about full germination at a temperature range from 10 to 30°C in light and darkness. The R-FR reversible photomechanism is present in both types of propagules. After 6 years the subterranean propagules were still a 100% viable, the aerial ones 85—90%. Seedlings derived from subterranean propagules are larger, develop faster and are more drought resistant than their “aerial” counterparts. The “subterranean” seedlings reach the first flowering cycle i. e. the one producing subterranean propagules only slightly earlier than the “aerial” seedlings, but flower much earlier in their second cycle which produces aerial propagules. Irrigated plants develop fewer, smaller and lighter aerial and fewer or none subterranean propagules in comparison with non irrigated plants. The ecological implications of these facts in connection with field observations on the behaviour of the plant in situ are discussed.