Early Growth Stages of the Rare Acridocarpus orientalis in the UAE—A First Step towards Conservation

doi:10.4236/nr.2012.31001

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Natural Resources, 2012, 3, 1-5

http://dx.doi.org/10.4236/nr.2012.31001 Published Online March 2012 (http://www.SciRP.org/journal/nr) 1

Early Growth Stages of the Rare Acridocarpus orientalis

in the UAE—A First Step towards Conservation

Taoufik Ksiksi1, Chedia Guenaoui2, Nael Fawzi1,3

1Biology Department, Faculty of Science, United Arab Emirates University, Al Ain, UAE; 2Arid Regions Institute, Medenine, Tuni-

sia; 3Flora & Phyto-Taxonomy Research Department, Agricultural Research Center, Giza, Egypt.

Email: [email protected]

Received January 11th, 2012; revised February 14th, 2012; accepted February 25th, 2012

ABSTRACT

The seed germination and seedling estab lishment of the rare Acridocarpus orientalis were investigated to understand its

requirements for further seedlings estab lishment in the United Arab Emirates (UAE). It is an important first step in or-

der to try to conserve the species and prevent its disappearance. The experiments were carried out in a greenhouse and

in a laboratory under a temper ature of about 25˚C ± 4˚C. Seeds were soaked in water or kept in cold conditions. A con-

trol treatment was also included. Only a total of 9 seeds emerged during a period that exceeded eight months. Percent

germination in the laboratory experiment reached a maximum of 32%, 75 days into the trial. The rate of seed mortality

was 64%. It may be a problem of acclimation to the greenhouse environment. The results of this study showed that A.

orientalis seeds were not dormant. About 32% of seeds germinated and all others were viable. Soaking seeds in water

proved to be the best treatment for A. orientalis to emerge. Further investigations of the species germination and estab-

lishment are needed in order to improve our c ha nc es of protecting A. orientalis in the wild.

Keywords: Qafas; Seed Germination; Seed Mortality

1. Introduction

The United Arab Emirates (UAE), like the other Golf

states, is facing severe environmental challenges mainly

because of economic development and urbanization,

which resulted in higher pressures on demands for the

natural resources. Climatic cond itions coupled with anth-

ropogenic activities are causing much of the pressure on

the natural ecosystems. The anthropogenic factors are the

prime cause of degradation [1]. The UAE is chara-

cterized by a bi-seasonal Mediterranean climate with high

temperatures and low rainfall. Like in any desert domi-

nated regions, soils are poor in organic matter, with

relatively low biological activities. Such harsh cond itions

result in extreme losses of vegetation cover and floral

biodiversity [2]. Much of these ecosystems are becoming

increasingly degraded from Dubai to Abu Dhabi [3]. In

arid and semiarid climate zones, desertification, land

degradation and declining precipitation rates increasingly

limit crop cultivation [4]. Additionally, widespread soil

salinity restricts the potential of recovery in many parts

of the UAE desert ecosystems. For instance, Haloxylon

salicornicum, only slightly tolerant of salt, is replaced by

Zygophyllum qatarense as soil salinity is increasing [5].

Numerous recent studies indicated that the natural

heritage of Abu Dhabi is threatened by urbanization,

infrastructure development, population growth and over-

grazing. Habitat loss and degradation and species loss are

expected to be detrimental outcomes. Overgrazing, for

instance, had a serious effect on the natural vegetation,

especially palatable plant species as a result of increased

grazing pressures [6]. A decline in floral diversity is a

direct, and sometimes irreversible, outcome of such

increased pressure. Overgrazing has already led to the

disappearance of Rhanterium epapposum and Panicum

turgidum in many parts of the UAE [5]. In addition to R.

epapposum, some palatable perennial grasses have sub-

stantially declined due to overgrazing [7]. Some shrubs

may replace other more palatable ones as a result of

heavy grazing. Some studies reported that other species

are replacing R. epapposum in central Saudi Arabia [8],

northern Africa [9] and Kuwait [10]; due to overgrazing.

For instance, Zygophyllum manda villei was th ought to be

widespread in the interior of the UAE, is actually res-

tricted to a small area of Southern Arabia [11].

Long-term management decisions are to be adopted to

reverse the downward trend in species, cover and biodi-

versity loss in the UAE deserts. Much of the benefits of

biodiversity could be restricted. Acridocarpus orientalis

is one species that has many ecological as well as

medicinal advantages. It is rare and prone to extinction.

The current field work led by the authors show that only

Early Growth Stages of the Rare Acridocarpus orientalis in the UAE—A First Step towards Conservation

less than 200 individuals are present in the wild. It is

only restricted to a small area within Jebel Hafit [12]. But

its current status in the UAE is unknown. Informatio n on

its growth habits will be a good start for proper mana-

gement. Combined laboratory and field approaches are

believed to be an adequate strategy to try to understand

the growth habits of A. orientalis. Transplanting green-

house grown plants could be an effective method to in-

troduce A. umbellata, a rare and threatened species

indigenous to the Pacific Coast of North America [13].

This will assist successes of reintroduction for con-

servation purposes, especially for species with few

remaining wild populations [13]. Descriptions of effe-

ctive procedures for these plant propagation and estab-

lishment in the field are decisive to progress the practice

of species re-establishment [14]. The efficiency of this

alternative was also justified by [15].

The present project attempts at understanding some of

the germination requirements of A. orientalis. The study

of seed germination is the first step in such conservation

approach [16]. Specifically here in the UAE, wher e there

is a lack of knowledge about the vegetation [3]. Improved

understanding of the germination requirements of any

plant species, and in particular the rare and endemic spe-

cies, is of crucial importance for its conservation and

management. The primary objective of this work is to

understand the germination characteristics of A. orient-

talis and ultimately create a nursery of that could be used

to rehabilitate ecosystems where it was once growing

within the UAE. In this part we focused on the germina-

tion from seeds as a step to produce seedlings.

2. Material and Methods

2.1. Study Site

United Arab Emirates (UAE) is surrounded by the Per-

sian Gulf to the north, Sultanate of Oman and Saudi Ara-

bia to the south, the Gulf of Oman and Sultanate of

Oman to the east, and Qatar and Saudi Arabia to the west.

The UAE is located between latitudes 22 degrees and

26.5 degrees north, and longitudes 51 degrees and 56.5

degrees east. Abu Dhabi is the largest Emirate in the

UAE, with an area of 67,340 km2, which constitute about

87% of the UAE total area. The remaining few wild A.

orientalis individuals are concentrated in a small wadi (a

dry river) within Jabal Hafeet mountain (E55˚46' and N

24˚05'), the highest peak in Abu Dhabi Emirate.

2.2. Variables Measured

Seeds of A. orientalis were collected between September

2009 and February 2010. Two different experiments we re

carried out. The first was conducted in the UAE Uni-

versity greenhouse (October 2009), in which temperature

was controlled by cooling chillers, and the second was

conducted in the ecology labo ra tory (February 20 10) . For

the greenhouse trial, seeds were d ivided into th ree gro up s.

The first group was sown directly without submitting any

treatment (Control), the second group was soaked in water

and the third group was treated by cold temperature before

their germination. The aim was to assess the best pre-

plantation treatment on emergence. Seeds were then planted

directly in 5-liter pots and placed in the greenhouse,

where the ambient temperature was 25˚C (±4˚C) and

under the natural day/night cycle.

For the laboratory trial, seeds of A. orientalis were

soaked in water during 48 hours at ambient temperature

(25˚C to 28˚C). After soaking, ten seeds per replicate

were placed within an incubator (Binder ®) in 9 cm di-

ameter Petri dishes, with a cotton layer that was regularly

moistened to saturation with distilled water. The aim was

to prevent dehydration during germination. The incubator

was pre-set to a constant temperature of 23˚C with a cycle

of 10 hours light and 14 hours dark. For this second as-

say, 250 seeds were used with 25 replicates. Seeds were

considered as germinated when the radical reached more

than 1 mm in length [17]. Recording of germinated seeds

was stopped when there was no further germination for

one week. The number of germinated seeds was recorded

daily and the Mean Time to Germinate (MTG) and the %

germination were determined. Photos were taken for

germinated seeds in all germination stages.

3. Results

The results of the greenhouse trial demonstrated that the

different seed treatments did not result in high sprouting

rates. Only a total of 9 seeds emerged during a period

that exceeded eight months. The first plants emergence

was recorded in 25/11/2009 where 2 seedlings emerged

from the water treated seeds and 1 plant emerged from

the cold treated ones. Four more plants emerged later in

9/12/2009 then 2 more plants emerged in 16/12/2009, all

from the water treated seeds. No plants emerged from the

non treated seeds. In 15//03/2010 one plant from the

water treated died. In 25/03/2010 two other plants (also

water treated seeds) were dead. There were no significant

differences between plants issued from water and cold

treated seeds (Figure 1) that reached the same growth

stage and all of them reached 8 leaves in May 2010.

The laboratory experiment showed a relatively higher

percent germination of 32%, 75 days into the trial

(Figure 2). However, the rate of seed mortality was 64%.

The majority of the mortality cases occurred right after

seeds germination. Seeds germinated after 2 to 7 days

and the MTG in this assay was 27 days.

The beginning of the radical emergence occurred one

week into the trial. Close observations of the seed

germination processes revealed that this species has lon g

and well developed roots. As it is shown in Figure 3,

Early Growth Stages of the Rare Acridocarpus orientalis in the UAE—A First Step towards Conservation

25-02-2010 19-03-2010 23-04-2010 06-05-2010

(a)

21-02-2010 19-03-2010 06-05-2010

(b)

Figure 1. Acridocarpus or ientalis gro wth sta ges in the gr eenhou se as a res ult of cold tr eated s eeds (a) and wate r trea ted seeds (b).

Figure 2. Cumulative germination and mortality rates of Acridocarpus orientalis seeds.

1 9

13 1726

54 59

Figure 3. Acridocarpus orientalis germination and radical emergence stages. Days since start of germination are shown.

Early Growth Stages of the Rare Acridocarpus orientalis in the UAE—A First Step towards Conservation

the emergence and the growth rate of these roots is very

fast. The aerial part showed also a rapid growth rate. The

first leaf emerged 1 to 3 weeks after root emergence. The

plants continued to develop its root system even after leaf

emergence.

The biggest problem encountered during this germi-

nation trial is the mortality of germinated and non-ger-

minated seeds. Many seeds died before their germination,

but a considerable number died at the stage of 2, 3 and

even 6 leaves.

Even if the laboratory essay showed a higher rate of

seed germination, no seedlings could survive to the end

of the experiment. However, six plants issued from the

directly sowed seeds in pots in the greenhouse are still

surviving. It may be a problem of acclimation to the

greenhouse environment.

4. Discussion

The results of this study showed that A. orientalis seeds

were not dormant. In fact, 32% of seeds germinated and

all the non-germinated seeds were viable. The higher

percent germination was observed with seeds soaked in

water. This can be explained by the removal of the

viscous layer coating all seeds of A. orientalis, after

being soaked in water. This result confirmed that of re-

ports [18] indicating that all the priming treatments

improved the emergence, seedling growth and reserve

metabolism.

The rate of germinated seed mortality, underline the

need for further future investigations into post germi-

nation conditions and acclimation.

Observations of root growth revealed the ability of this

species to survive in dry regions. It developed long

principal roots with many secondary roots, which high-

light the ability of A. orientalis to extract soil moisture

even in deep substrate levels. The potential water uptake

in any soil layer depends on the soil water content and

the root density, and for whole soil profiles water uptake

depends on the rooting depth and total root length [19].

5. Conclusion

This study provided some much needed information

about the germination conditions and the growth stages

of the rare plants species A. orientalis. However, the lack

of information on its growth requirements is urgently

needed to be addressed, in order to overcome A. orien-

talis rare status in the UAE. Additionally, improved un-

derstanding of the species soil and habitat preferences,

through soil nutrient analysis within its niche in Jabal

Hafeet are also required. Ecological interactions of the

species could offer more information about the growth

conditions of A. orientalis, which will certainly improve

the rate of success to protect it.

6. Acknowledgements

The funding by the Mohamed bin Zayed Species Con-

servation Fund is much appreciated (Fund No. 21S031).

The investigators would also like to express their sincere

appreciation to the Office of Research Support and

Sponsored Projects at the United Arab Emirates Univer-

sity for their support and the management of this project.

The support from the Biology Department and the Fac-

ulty of Science is also much appreciated. Assistance from

all students in any parts of this project is appreciated.

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