During germination, the most resistant stage of the life cycle - the seed - changes to the most sensitive stage, namely the seedling. Therefore, in desert plant species, seed dispersal and subsequent germination in the optimum place are particularly critical parameters. Discussed here are the ways and means by which desert plants have adapted through the course of evolution to their extreme environment. Two such strategies which have evolved are outlined: plants with relatively large and protected seeds which germinate when the chance of seedling survival is high and the risk relatively low; and those with an opportunistic strategy - minute seeds which germinate after low rainfall. The reader is provided with an understanding of the complex influences acting upon each seed, traced from initial development to germination stage, regarding germination preparation and the subsequent survival.

Seed Germination in Desert Plants

Preface 1 Introduction SA Ghazanfar, M Fisher 2 Climate M Fisher, DA Membery 3 Geology and Geomorphology I Guba, K Glennie 4 Biogeography and Introduction to Vegetation H Kurschner 5 Bryophytes and Lichens H Kurschner, SA Ghazanfar 6 Montane and Wadi Vegetation U Deil, A-N al Gifri 7 Vegetation of the Plains SA Ghazanfar 8 Vegetation of the Sands JP Mandaville 9 Coastal and Sabkha Vegetation U Deil 10 Water Vegetation SA Ghazanfar 11 Plants of Economic Importance SA Ghazanfar 12 Biodiversity and Conservation M Fisher, et al References Index

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Vegetation of the Arabian Peninsula

Limonium stocksii (Boiss.) Kuntze (Plumbaginaceae) is a perennial, woody shrub distributed at Hawks Bay, Karachi, Pakistan. Experiments were carried out to investigate seed germination responses of...

Effect of light, salinity, and temperature on seed germination of Limonium stocksii

Suaeda moquinii (Torrey) Greene (desert blite), a succulent shrub in the family Chenopodiaceae, is widely distributed in salt marshes of the western United States. Suaeda moquinii produces dimorphic seeds (soft brown and hard black). Both types of seeds were collected from a salt marsh in Faust, Utah. Experiments were conducted to determine the seed germination responses of the black and brown seeds to salinity and temperature. Brown seeds were found to be one of the most salt tolerant at the germination stage when compared to other halophytes. Brown seeds germinated (30%) at 1000 mM NaCl, but only a few black seeds germinated (8%) at 600 mM NaCl. Seed germination occurred in most saline treatments at the lowest thermoperiod (5–15˚C) tested. In some salinity treatments (600, 800, 1000 mM), further increases in temperature resulted in progressively decreased seed germination. Brown seeds germinated better and had a higher germination rate (germination velocity) than black seeds at all thermoperiods. The highest rate of germination of black seeds occurred at the lowest thermoperiod (5–15˚C). Recovery of germination for black seeds when transferred to distilled water after being in various salinity treatments for 20 days was nearly complete (82–100%) at the lowest thermoperiod (5–15˚C) but decreased with increase in the temperature. Brown seeds recovered substantially (59–97%) from salinity at all thermoperiods. Regression analyses indicated significant differences between the germination recovery of the black and brown seeds.

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S. Abdul Baset

Papers

Germination of two halophytes: Halopeplis perfoliata and Limonium axillare from Saudi Arabia

Germination of Verbesina enceliodies and Rumex nervosus from South Hijaz