SEED-GERMINATION IN ACACIA SPECIES AND THEIR RELATION TO ALTITUDINAL GRADIENT IN SOUTH-WESTERN SAUDI-ARABIA

Seed germination of Acacia species found in south-western Saudi Arabia responded in three different ways to temperature: (1) Germination over a broad range of temperature (between 10 and 40 degrees C) was recorded in Acacia asak, A. ehrenbergiana, A. iraqensis, A. hamulosa and A. tortilis ssp. spirocarpa. (2) Cold-evading germination (between 20 and 40 degrees C) was recorded in A. oerfota. (3) Heat-evading germination (between 10 and 35 degrees C) was recorded in A. origena. Plants of the first two types were found in desert to semi-desert environments between sea level and 2000 m, whereas plants of the third type occur in a cool temperature environment between 1750-2500 m. A strong correlation exists between seed germination, temperature, water and thickness of seed coat. (C) 1995 Academic Press Limited