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Germination characteristics of nine species from Abha
Journal of Arid Environments (1983) 6, 247-251
Germination characteristics of nine species from Abha H. A. Abulfatih ,. Accepted 6]uly 1982 Seed germination of nine species of common shrubs and herbs was examined in moisture and temperature gradients. In response to moisture, two types of seeds were distinguished. One (which included Argemone mexieana, Datura stramonium, Marubium vulgare, Rumex nervosus, Verbesina eneelioides and Solanum incanum) showed a relatively high percentage of germination on the wet side of the gradient. The other (which is represented by Lavandula dentata, Rosaabyssinica and Withania somnifera) showed a relatively high percentage of germination on soils of intermediate moisture content. Seeds of most species, germinated well under cold and moderate temperatures. Rumex nervosus and V. eneelioides germinated on a relatively broad range of temperatures. Rosa abyssinica and S. incanum did not respond to temperature. Seeds which showed a good response to moisture and temperature gradients were commonly related to highly aggressive and widely distributed types of species. The best example was V. eneelioides.
Introduction Abha is located on the highlands of Asir in south-western Saudi Arabia. The area is characterized by mild temperature during summer and a cold winter. Rainfall is to be expected throughout the year especially in summer and spring. Various microhabitats are formed as a result of the topographic complexity. Two major vegetation types are formed in the area. They are the woodlands of Juniperus procera at high elevation and scattered trees of Acacia sp. on the rolling lands at lower elevation (Abulfatih, 1979). In such environments, seeds of most species germinate during winter. It was shown by Mahmoud, EI-Sheikh et al. (1981) that seeds of Verbesina encelioides and Rumex neruosus collected from different geographical areas of the Asir Highlands responded differently to temperature. They germinated over a temperature range of 5-40°Cand also over a range of alternating temperatures (18/8,21/10,25/15,31/16 and 36/21°C). In the present study, nine common shrubs and herbaceous plants were chosen, and their seed germination tested in moisture and temperature gradients. These species were; Argemone mexicana, Datura stramonium, Lavandula deniata, Marubium vulgare, Rosa abyssinica, R. nervosus, V. encelioides, Withania somnifera and Solanum incanum. Materials and methods Germination in temperature and moisture gradients was tested on seeds of nine species collected from Abha and its surroundings, in 1980. These species were; A. mexicana, D. stramonium, L. dentata, M. vulgare, Rosa abyssinica, R. nervosus, V. encelioides, W.
* College of Education, Abha, P.O. Box 932, Saudi Arabia 0140-1963/83/030247 +05 $03.00/0
([\ 1983 Academic Press Inc. (London) Limited
248
H. A. ABULFATIH
somnifera, and S. incanum. These experiments were carried out at the Collegeof Education, 15 km east of Abha. A gradient of temperature was established using an aluminum bar with one end immersed in water at 65°C and the other in melting ice at 4°C. The surface ofthe bar was divided into six temperature zones. For each species, nine groups of 10 seeds each were distributed along the temperature bar. Each group of seeds was placed on filter paper, fenced in with a wall of modelling clay 1 em high, and covered by a glass plate to reduce evaporation and keep the seeds moist. The seeds were dampened with distilled water every day. Thermocouples were attached to the gradient bar under each batch of seeds to measure temperature, which ranged from 8 to 40°C. Light was provided by two 40 W cool, white fluorescent tubes switched on throughout the experiment. The design of the temperature gradient bar was based on those made by Goloff (1973) and Abulfatih & Bazzaz (1979). Seed germination was also studied in the open on a soil moisture gradient. This experiment was conducted during March of 1980. March was chosen since it is the normal time for seed germination and seedling emergence for the majority of the plants in Asir area. The gradient was an inclined wooden box (50 x 50 x 120 em) divided into six compartments by perforated walls, filled with sandy loam soil. The soil was watered for 7 days before sowing to establish a moisture gradient, and later watered every day at the lower end. In each compartment, 100 seeds were sown at 0·5 em depth, and seedling emergence was recorded. Soil samples were taken from the top 2 em of each compartment once a week at 0800 and 1600h, and average soil moisture determined gravimetrically. Soil moisture ranged between 4·4 and 16 per cent. The moisture gradient bar is modified from those of Pickett & Bazzaz (1976) and Abulfatih & Bazzaz (1979).
Results Of the nine species tested on the temperature gradient, seven germinated. Rosa abyssinica and S. incanum showed no sign of germination. Most of the seven species germinated best on the cold side of the gradient. Verbesinia encelioides and R. neruosus showed a relatively broad response to temperature, germinating between 8 and 33·6°C: A. mexicana showed a relatively little germination and only at 14·4°C (Fig. 1). Each of the nine species showed a specific response to the soil moisture gradient between 4·4 and 16 per cent moisture content. Two major germination trends were distinguished. One group of species showed a relatively high percentage of germination at 16 per cent soil moisture. This included A. mexicana, D. stramonium, M. vulgare. R. neroosus, V. encelioides, and S. incanum, The second group showed a relatively high percentage of germination at 11·4 per cent soil moisture. This was exemplified by L. dentata, Rosa abyssinica, and W. somnifera. Seeds of W. somnifera showed an exceptionally wide response to moisture, germinating between 6.7 and 16 per cent soil moisture. Seeds of A. mexicana andM. vulgare only germinated on the wet side of the gradient, between 13·7 and 16 per cent soil moisture, and even here they showed a very low percentage of germination.
Conclusion Seeds of the nine species used in this work showed various potentials for germination in temperature and moisture gradients. Seeds of most species germinated well at cold or moderate temperatures. A relatively high germination percentage was recorded in soils of
249
GERMINATION CHARACTERISTICS 100
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Figure 1. Seed germination along temperature (e - - e) and moisture(0--0) gradients. On temperature gradient, numbers 1,2,3,4,5 and 6 correspond to 8,14·4,20'8,27'2,33'6 and 40°C. On moisture gradient, numbers 1,2,3,4,5 and 6 correspond to 16,13'68,11'36,9'04,6'72 and 4·4 per cent moisture. (a) Argemone mexicana; (b) Datura stramonium; (c) Lauandula dentata; (d) Marubium vulgare; (e) Rosa abyssinica; (f) Rumex nervosus; (g) Verbesina encelioides; (h) Withania somnifera; (i) Solanum incanum.
high or moderate moisture content. No germination took place in very dry soil or at high temperature. Seeds that showed a positive response to temperature and moisture were commonly related to highly aggressive and widely distributed types of species. From the experimental results and field observations it can be said that V. encelioides, R. neruosus and D. stramonium are good examples. In the areas around the city of Abha, germination and emergence normally take place during the cold, rainy month of March (Table 1). This observation is explained by the experimental results which indicate that the majority of species favor low temperature and high soil moisture for seed germination. References Abulfatih, H. A. (1979). Vegetation of higher elevation of Asir, SaudiArabia. Proceedings of Saudi Biological Society, 3: 139-148.
21·8 17·4 5·5 6·0 24·0 98·0 92·0 10·0 35·5
Abs. max. temp. CCq Mean max. temp. (oq Abs. min. temp. (oq Mean min. temp. (oq Rainfall (mm) Abs. max. R. H. Mean max. R. H. Abs. min. R. H. Mean min. R. H.
22·5 17·5 6·8 10·7 4·9 98·0 94·0 13·0 41·0
Feb 22·6 19·7 8·8 12·1 38·8 98·0 90·5 16·5 39·5
Mar 26·4 21·9 10·4 13·1 45·3 97·0 83·5 15·5 33·0
Apr 29·0 24·7 8·6 15·0 60·4 98·0 78·5 15·0 28·0
May 30·2 28·1 15·6 17·8 7·3 98·0 70·0 9·0 17·5
June 29·4 26·5 1l·6 16·4 47·9 98·0 75.,5 10·0 31·0
July
Mean annual wind speed = 9·5 km/h; mean maximum wind speed = 12·7 km/h.
Jan
Climatic condition
Month
29·0 26·7 12·1 17·1 44·8 98·0 77·0 9·0 19·5
Aug 28·9 24·9 12·4 15·5 9·5 98·0 69·0 6·5 15·5
Sept
temperature, rainfall, relative humidity and wind speed
26·4 23·7 10·4 12·5 34·5 98·0 84·0 9·0 18·0
Oct 24·3 19·1 8·7 10·4 14·7 97·0 93·5 20·0 39·5
Nov
Table 1. Climatic recordsofAbha for the period between 1976 and 1978, showing air
22·0 18·6 6·6 9·6 0·7 98·0 81·5 12·0 31·0
26·0 22·4 9·9 13·0 27·7 97·8 82·4 12·1 29·1
Dec Mean monthly
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Abulfatih, H. A. & Bazzaz, F. A. (1979). The biology of Ambrosia trfida L.U. Germination, emergence, growth and survival. New Phytologist, 83: 817-827. Goloff, A. A. (1973). A germination model for natural seed populations. Ph. D. thesis, University of Illinois, Urbana. Mahmoud, A., EI-Sheikh, A. M. & Abdul Baset, S. (1981). Germination ofVerbesina encelioides and Rumex nervosus from south Hijaz. Journal ofArid Environments, 4: 299-308. Pickett, S. T. A. & Bazzaz, F. A. (1976). Divergence of two co-occuring successional annuals on a soil moisture gradient. Ecology, 57: 169-176.
Germination characteristics of nine species from Abha H. A. Abulfatih ,. Accepted 6]uly 1982 Seed germination of nine species of common shrubs and herbs was examined in moisture and temperature gradients. In response to moisture, two types of seeds were distinguished. One (which included Argemone mexieana, Datura stramonium, Marubium vulgare, Rumex nervosus, Verbesina eneelioides and Solanum incanum) showed a relatively high percentage of germination on the wet side of the gradient. The other (which is represented by Lavandula dentata, Rosaabyssinica and Withania somnifera) showed a relatively high percentage of germination on soils of intermediate moisture content. Seeds of most species, germinated well under cold and moderate temperatures. Rumex nervosus and V. eneelioides germinated on a relatively broad range of temperatures. Rosa abyssinica and S. incanum did not respond to temperature. Seeds which showed a good response to moisture and temperature gradients were commonly related to highly aggressive and widely distributed types of species. The best example was V. eneelioides.
Introduction Abha is located on the highlands of Asir in south-western Saudi Arabia. The area is characterized by mild temperature during summer and a cold winter. Rainfall is to be expected throughout the year especially in summer and spring. Various microhabitats are formed as a result of the topographic complexity. Two major vegetation types are formed in the area. They are the woodlands of Juniperus procera at high elevation and scattered trees of Acacia sp. on the rolling lands at lower elevation (Abulfatih, 1979). In such environments, seeds of most species germinate during winter. It was shown by Mahmoud, EI-Sheikh et al. (1981) that seeds of Verbesina encelioides and Rumex neruosus collected from different geographical areas of the Asir Highlands responded differently to temperature. They germinated over a temperature range of 5-40°Cand also over a range of alternating temperatures (18/8,21/10,25/15,31/16 and 36/21°C). In the present study, nine common shrubs and herbaceous plants were chosen, and their seed germination tested in moisture and temperature gradients. These species were; Argemone mexicana, Datura stramonium, Lavandula deniata, Marubium vulgare, Rosa abyssinica, R. nervosus, V. encelioides, Withania somnifera and Solanum incanum. Materials and methods Germination in temperature and moisture gradients was tested on seeds of nine species collected from Abha and its surroundings, in 1980. These species were; A. mexicana, D. stramonium, L. dentata, M. vulgare, Rosa abyssinica, R. nervosus, V. encelioides, W.
* College of Education, Abha, P.O. Box 932, Saudi Arabia 0140-1963/83/030247 +05 $03.00/0
([\ 1983 Academic Press Inc. (London) Limited
248
H. A. ABULFATIH
somnifera, and S. incanum. These experiments were carried out at the Collegeof Education, 15 km east of Abha. A gradient of temperature was established using an aluminum bar with one end immersed in water at 65°C and the other in melting ice at 4°C. The surface ofthe bar was divided into six temperature zones. For each species, nine groups of 10 seeds each were distributed along the temperature bar. Each group of seeds was placed on filter paper, fenced in with a wall of modelling clay 1 em high, and covered by a glass plate to reduce evaporation and keep the seeds moist. The seeds were dampened with distilled water every day. Thermocouples were attached to the gradient bar under each batch of seeds to measure temperature, which ranged from 8 to 40°C. Light was provided by two 40 W cool, white fluorescent tubes switched on throughout the experiment. The design of the temperature gradient bar was based on those made by Goloff (1973) and Abulfatih & Bazzaz (1979). Seed germination was also studied in the open on a soil moisture gradient. This experiment was conducted during March of 1980. March was chosen since it is the normal time for seed germination and seedling emergence for the majority of the plants in Asir area. The gradient was an inclined wooden box (50 x 50 x 120 em) divided into six compartments by perforated walls, filled with sandy loam soil. The soil was watered for 7 days before sowing to establish a moisture gradient, and later watered every day at the lower end. In each compartment, 100 seeds were sown at 0·5 em depth, and seedling emergence was recorded. Soil samples were taken from the top 2 em of each compartment once a week at 0800 and 1600h, and average soil moisture determined gravimetrically. Soil moisture ranged between 4·4 and 16 per cent. The moisture gradient bar is modified from those of Pickett & Bazzaz (1976) and Abulfatih & Bazzaz (1979).
Results Of the nine species tested on the temperature gradient, seven germinated. Rosa abyssinica and S. incanum showed no sign of germination. Most of the seven species germinated best on the cold side of the gradient. Verbesinia encelioides and R. neruosus showed a relatively broad response to temperature, germinating between 8 and 33·6°C: A. mexicana showed a relatively little germination and only at 14·4°C (Fig. 1). Each of the nine species showed a specific response to the soil moisture gradient between 4·4 and 16 per cent moisture content. Two major germination trends were distinguished. One group of species showed a relatively high percentage of germination at 16 per cent soil moisture. This included A. mexicana, D. stramonium, M. vulgare. R. neroosus, V. encelioides, and S. incanum, The second group showed a relatively high percentage of germination at 11·4 per cent soil moisture. This was exemplified by L. dentata, Rosa abyssinica, and W. somnifera. Seeds of W. somnifera showed an exceptionally wide response to moisture, germinating between 6.7 and 16 per cent soil moisture. Seeds of A. mexicana andM. vulgare only germinated on the wet side of the gradient, between 13·7 and 16 per cent soil moisture, and even here they showed a very low percentage of germination.
Conclusion Seeds of the nine species used in this work showed various potentials for germination in temperature and moisture gradients. Seeds of most species germinated well at cold or moderate temperatures. A relatively high germination percentage was recorded in soils of
249
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Figure 1. Seed germination along temperature (e - - e) and moisture(0--0) gradients. On temperature gradient, numbers 1,2,3,4,5 and 6 correspond to 8,14·4,20'8,27'2,33'6 and 40°C. On moisture gradient, numbers 1,2,3,4,5 and 6 correspond to 16,13'68,11'36,9'04,6'72 and 4·4 per cent moisture. (a) Argemone mexicana; (b) Datura stramonium; (c) Lauandula dentata; (d) Marubium vulgare; (e) Rosa abyssinica; (f) Rumex nervosus; (g) Verbesina encelioides; (h) Withania somnifera; (i) Solanum incanum.
high or moderate moisture content. No germination took place in very dry soil or at high temperature. Seeds that showed a positive response to temperature and moisture were commonly related to highly aggressive and widely distributed types of species. From the experimental results and field observations it can be said that V. encelioides, R. neruosus and D. stramonium are good examples. In the areas around the city of Abha, germination and emergence normally take place during the cold, rainy month of March (Table 1). This observation is explained by the experimental results which indicate that the majority of species favor low temperature and high soil moisture for seed germination. References Abulfatih, H. A. (1979). Vegetation of higher elevation of Asir, SaudiArabia. Proceedings of Saudi Biological Society, 3: 139-148.
21·8 17·4 5·5 6·0 24·0 98·0 92·0 10·0 35·5
Abs. max. temp. CCq Mean max. temp. (oq Abs. min. temp. (oq Mean min. temp. (oq Rainfall (mm) Abs. max. R. H. Mean max. R. H. Abs. min. R. H. Mean min. R. H.
22·5 17·5 6·8 10·7 4·9 98·0 94·0 13·0 41·0
Feb 22·6 19·7 8·8 12·1 38·8 98·0 90·5 16·5 39·5
Mar 26·4 21·9 10·4 13·1 45·3 97·0 83·5 15·5 33·0
Apr 29·0 24·7 8·6 15·0 60·4 98·0 78·5 15·0 28·0
May 30·2 28·1 15·6 17·8 7·3 98·0 70·0 9·0 17·5
June 29·4 26·5 1l·6 16·4 47·9 98·0 75.,5 10·0 31·0
July
Mean annual wind speed = 9·5 km/h; mean maximum wind speed = 12·7 km/h.
Jan
Climatic condition
Month
29·0 26·7 12·1 17·1 44·8 98·0 77·0 9·0 19·5
Aug 28·9 24·9 12·4 15·5 9·5 98·0 69·0 6·5 15·5
Sept
temperature, rainfall, relative humidity and wind speed
26·4 23·7 10·4 12·5 34·5 98·0 84·0 9·0 18·0
Oct 24·3 19·1 8·7 10·4 14·7 97·0 93·5 20·0 39·5
Nov
Table 1. Climatic recordsofAbha for the period between 1976 and 1978, showing air
22·0 18·6 6·6 9·6 0·7 98·0 81·5 12·0 31·0
26·0 22·4 9·9 13·0 27·7 97·8 82·4 12·1 29·1
Dec Mean monthly
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GERMINATION CHARACTERISTICS
251
Abulfatih, H. A. & Bazzaz, F. A. (1979). The biology of Ambrosia trfida L.U. Germination, emergence, growth and survival. New Phytologist, 83: 817-827. Goloff, A. A. (1973). A germination model for natural seed populations. Ph. D. thesis, University of Illinois, Urbana. Mahmoud, A., EI-Sheikh, A. M. & Abdul Baset, S. (1981). Germination ofVerbesina encelioides and Rumex nervosus from south Hijaz. Journal ofArid Environments, 4: 299-308. Pickett, S. T. A. & Bazzaz, F. A. (1976). Divergence of two co-occuring successional annuals on a soil moisture gradient. Ecology, 57: 169-176.