American Journal of Plant Sciences, 2011, 2, 484-495
doi:10.4236/ajps.2011.23057 Published Online September 2011 (http://www.SciRP.org/journal/ajps)
Seed Morphology of Some Species of Indigofera
(Fabaceae) from Saudi Arabia (Identification
of Species and Systematic Significance)
F. A. Al-Ghamdi
Biology Department, Faculty of Science, KAU, Jeddah, KSA.
Received May 19th, 2011; revised June 13th, 2011; accepted July 28th, 2011.
ABSTRACT
Seeds of 18 species of Indigofera L. were examined with the scanning electron microscope and the light microscope.
Macro- and micromorphological characters, including seed shape, colour, size, surface, epidermal cell shape, anticli-
nal boundaries, outer periclinal cell wall and relief of outer cell walls, are presented. Two types of basic anticlinal cell
wall boundaries and two typ es of relief outer cell walls are recognized and two different shap es of the outer periclinal
cell wall are described. A key for the iden tification of the investigated taxa based on seed chara c ters is provided.
Keywords: Seeds, Morpholog y , Indigofera, Fabace ae, Saudi Arabia
1. Introduction
Indigofera L. is a large pantropical genus in Fabaceae,
belongs to the tribe Galegeae with c. 720 - 730 species
[1]. The majority of taxa occur in Africa (c. 520) with
other centres of diversity in Arabia to South East Asia,
Mexico to subtropical North and South America, Austra-
lia and Madagascar. About 280 speci es of Indigofera
occur in the flora of Southern Africa region [2,3].
In Saudi Arabia Indigofera is represented by about 20
species and five varieties [4,5].
Reference [14] discussed features of the Indigofera
fruit relevant to the Australian taxa. Reference [6] were
the first to recognize that all species have a persistent
fruit-base that remains with the calyx and staminal tube
after the valves of the open pod have fallen. Reference [1]
considered this is a synapomorphy for the tribe. Refer-
ence [7] found that all endemic species of Indigofera in
Australia have endocarp tannins present except in I. bai-
leyi and I. mackinlayi.
Reference [8] mentioned that the Scanning electron
microscopy provides great tool to achieve more accurate
seed identification, which could be used as a routine
technique in the study of the Spermoderm Morphology
[9,10].
Reference [11] established nine categories in his in-
vestigation of 340 species of Paplionoideae. Also, Ref-
erence [12] found three categories of Lersten’s estab-
lishments. Belonging to the seeds testa patterns, Refer-
ence [11] illustrated a simple reticulate in T. candida.
The aim of the present study is to investigate macro-
and micro-morphological characters of genus Indigofera
seeds in Saudi Arabia, using Stereo- and Scanning Elec-
tron microscopy, which expected to be reliable for dis-
tinguishing the studied taxa. The work is mainly concen-
trated on collection of field work as well as herbarium
collections from King Abdulaziz University KUH, KSU
and RIY.
2. Material and Methods
The fresh plant samples were collected from the sites
which were reported by [4,5,13,14], with field survey of
the species throughout Saudi Arabia regions. The plant
specimens nomenclatured according to [4,5,15]. Mature
seeds were collected from dehiscent legumes, then cle-
aned with alcohol and kept for drying. The macro-mor-
phological characters of the studied seeds were carried
out using of Stereo-microscopy (Stemi2000-C) and the
measurements, shapes, colour, and the position of hilum
were recorded. On the other hand, the mature seeds of
the investigated taxa were chosen for SEM study, where
seeds were mounted on stubs using double face carbon
tape, and coated with gold/palladium at 1.2 kv for 15
minutes under high vacuum in an ion sputter coating unit.
The examined samples were detected and photographed
using Scanning Electron Microscopy (Jeol JSM-20). The

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia 485
(Identification of Species and Systematic Significance)
terminology used here follows authors such as [10] and
[16].
3. Results
Fruit and Seed characters are very important to separate
among species in the genus Indigofera.
3.1. Fruits Colour
The colour of fruits is very important to separate among
the studied species. The colour varies from brown, light
brown, deep brown, grayish, creamer, deep brown to
creamer. It is deep brown in I. argentea and I. spicata,
light brown in I. sessiliflora and I. spiniflo ra, grayish in I.
Arabica and I. Linifolia, creamer in I. intricata, deep
brown to creamer in I. oblongifolia and brown in the rest
of the species. The fruit colour is used to distinguish be-
tween species of I. Arabica, I. Linifolia, I. intricata and I.
oblongifolia from the other species (see Table 1).
Table 1. The macro-morphological characters of the studied Indigofera s
ee ds.
Fruits Seeds
ornament. Taxa colour constriction
level len. (cm)shape numb e r (mean)colour hilum position size (mm) shape pr.colour
1. I. amorphoides Br. - 0.6 St., Cy.1 - 2(–3)Br. Subcentral0.21 × 0.16 Irr. - -
2. I. arabica Gr. - 1.3 Fl., Fic.4 Br. Central 0.17 × 0.14 Irr. - -
3. I. argentea D. Br. - 1.5 St., Cy.10 D. Br.Subcentral0.95 × 0.12 Rect. - -
4. I. arrecta Br. - 3.2 St., Cy.7 - 9 BlackSubcentral0.2 × 0. 15 Irr. - -
5. I. articulata Br. De. 1.1 ±De., Cy.3 - (–4)D. oilyCentral 0.22 × 0.22 Cir. - -
6. I. coerulea var. occidentalis Br. Sh. 1.7 De, Cy.5 L. oilyCentral 0.25 × 0.18 Rect. - -
7. I. colutea Br. - 1.5 St., Cy.6 Oily Subcentral0.15 × 0. 1 Cir. - -
8. I. hochstetteri Br. - 1.7 De., Fl.9 Br. Su b c entral0.18 × 0.16 Cir. + Br.
9. I. intricata Cr. - 2.5 St., Cy.15 L. Br ./Or.Subcentral0.14 × 0.13 Cir. - -
10. I. Linifolia Gr. - 0.3 Cir. 1 Br. Central 0.08 × 0.09 Cir. + Br.
11. I. oblongifol i a D. Br. to Cr. De. 2.2 ±De., Cy.6 Br. Subcentral0.14 × 0.1 Irr. - -
12. I. sessiliflora L. Br. De. 1.0 St., Cy.7 D. oilyCentral 0.11 × 0.11 Cir. + Gr. - oily
13. I. spicata D. Br. - 1.4 St., Cy.6 D. oilyCentral 0.14 × 0.14 Cir. + D. Br.
14. I. spiniflora L. Br. De. 3.5 Cu. 9 Br. Central 0.25 × 0.12 Irr. + Pu. to D. pu
15. I. spinosa Br. - 1.7 St., Cy.6 - 7 Cr. Subcentral0.15 × 0.13 Rect. + Oily-D. Br.
16. I. tinctoria Br. - 2.5 St., Cy.7 - 9 Oily/Gr.Subcentral0.25 × 0.16 Rect. + D. Br.
17. I. trita var. subulata Br. - 1. 0 - 2.5St., An.7 - 10D. Br.Subcentral0. 17 × 0.1 Irr. - -
18. I. volkensii Br. V. Sh. 1.5 - 2.0St., Cy.6 Br. Subcentral0.08 × 0 .1 Rect. + P u-Bl.
Bl. = black; Br. = brown; Cir. = circular; Cr. = creamer; Cu. = curved; D. Br. = dark brown; De. = deep; Gr. = grayish; De., Cy. = deflexed, cylindrical; ±De., Cy. =
little de f le xed, cylindrical; De., Fl. = deflexed, flat; Fl., Fic. = flat, fickle; Irr. = irregular; Len . = length; L. Br. = light br own; L. Br./Or. = light brown to orange;
Ornament. = ornamentation; Pr. = present; Pu. = purple; Rect. = rectangular; Sh. = shallow; V. Sh. = very shallow; St., An. = straight, angular, St., Cy. =
straight, c y li ndr ical .

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia
486 (Identification of Species and Systematic Significance)
3.2. Fruits Constriction Level
The level of fruits constriction also is important feature
to distinguish between even and constricted fruits in
studied species. The fruits have deep constrictions in I.
articulate, I. oblon gifolia, I. sessiliflora and I. spiniflora ,
with shallow cons trictions in I. coerulea var. occidentalis
and possess very shallow constrictions in I. volkensii.
The fruits of the remained studied species are even. The
Fruits constriction level is also useful to distinguish be-
tween species of I. articulate, I. oblongifolia, I. sessili-
flora, I. spiniflora, I. coerulea var. occidentalis and I.
volkensii. from the other investigated species (see Table
1).
3.3. Fruits Length
Length of fruits ranges from 0.6 cm - 3.5 cm (see Table
2). The smallest fruits are those of I. sp eci es (0 . 6 cm) a nd
the largest are those of I. spiniflora (3.5 cm). Fruits
length of other taxa ranged between (1.0 µm - 3.2 µm).
Fruits length contributes to differentiate between the
related species of I. amorphoides, I. spiniflora, I. ar-
recta (3 .2 cm ) from the ot her s p eci es ( Table 1).
3.4. Fruits Shape
Fruits are more or less similar in shape being straight,
cylindrical; deflexed, cylindrical; flat, fickle; deflexed,
flat; circular; curved or straight, angular. They are more
or little deflexed, cylindrical in I. articulate, I. coerulea
var. occidentalis and I. oblongifolia, Flat, fickle in I.
Arabica, Deflexed, flat in I. hochstetteri, circular in I.
Linifolia, curved in I. spiniflora and finally straight, an-
gular in I. trita var. subulata. The fruits shape also con-
tributes to differentiate I. articulate, I. coerulea var.
occidentalis, I. oblongifolia, I. Arabica, I. hochstetteri, I.
Linifolia, I. spiniflora and I. trita var. subulata. species
from the other investigated taxa which are characterized
by straight, cylindrical fruits (Table 1).
3.5. Seeds Number (Mean)
Number of seeds varies greatly among the examined taxa,
the high number of seeds is 15 seeds in I. intricata and
the low number is 1 - 2 in I. Linifolia and I. amorphoides,
while the number of seeds in the rest of the studied spe-
cies are ranged from 3 - 10 seeds. The seed number was
found useful to separate species of I. intricata, I. Linifolia
and I. amorphoides from the other species (see Table 1).
3.6. Seeds Colour
The colour of seeds is of high diagnostic and systematic
interest among taxa. The colour varies from brown, dark
oily, dark brown, oily, black, light oily, light brown/or-
ange and creamer to oily/grayish. The seeds colour is
brown in I. amorphoides, I. Arabica, I. hochstetteri, I.
Linifolia, I. oblongifolia, I. spiniflora and I. volkensii,
dark oily in I. articulata, I. sessiliflora and I. spicata,
dark brown in I. argentea and I. trita var. subulata, oily
in I. colutea, with black colour in I. arrecta, light oily
colour in I. coerulea var. occidentalis, light brown/or-
ange in I. intricate, creamer in I. spinosa and finally
oily/grayish in I. tinctoria. The Seeds colour is also used
to distinguish between species of I. arrecta, I. coerulea
var. occidentalis, I. intricate, I. spinosa and I. tinctoria
from the other investigated taxa where there are more
than one species for every colour (Figures 1-18 and Ta-
ble 1).
(a)
(b)
(c)
Figure 1. I. amorphoides: (a) enti re seed; (b) enl ar gement of
seed coat; ( c) H il um shape.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia 487
(Identification of Species and Systematic Significance)
(a) (b) (c)
Figure 2. I. arabica: (a) enti re seed; (b) enla rgement of seed coat; ( c ) H il um shape.
(a) (b) (c)
Figure 3. I. argentea: (a) entir e seed; (b) enl argement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 4. I. arrecta: (a) entire seed; (b) enlargement of seed coat; (c ) H il um shape.
3.7. Hilum Position
There are two forms to hilum position, it is may be sub-
central or central. Hilum is central in I. Arabica, I. ar-
ticulate, I. Linifolia, I. sessiliflora, I. spicata and I.
spiniflora and subcentral in the remained species. Posi-
tion of the hilum was useful to distinguish between two
groups in the studied taxa, group with subcentral hilum
and another one with central hilum (Figures 1-18 and
Table 1).

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia
488 (Identification of Species and Systematic Significance)
(a) (b) (c)
Figure 5. I. articulata: (a) ent ir e seed; (b) enla rgement of seed coat; ( c ) H il um shape.
(a) (b) (c)
Figure 6. I. coerulea var. occidentalis: (a) entire seed; (b) en largement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 7. I. colute a : (a) entire seed; (b) enlargement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 8. I. hochstetteri: (a) enti re seed; (b) enlargement of seed coat; (c) H il um shape.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia 489
(Identification of Species and Systematic Significance)
(a) (b) (c)
Figure 9. I. intricate: (a) entir e seed; (b) enl argement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 10. I. linifolia: (a) entir e seed; (b) enl argement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 11. I. oblongifolia: (a) enti re seed; (b) enlargement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 12. I. sessiliflora: (a) entire seed; (b) enlargement of seed coat; (c) H il um shape.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia
490 (Identification of Species and Systematic Significance)
(a) (b) (c)
Figure 13. I. spicata: (a) enti re seed; (b) en largement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 14. I. spicata: (a) enti re seed; (b) en largement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 15. I. spinosa: (a) enti re seed; (b) en largement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 16. I. tinc t or i a: (a) entire seed; (b) enlargement of seed coat; (c) H il um shape.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia 491
(Identification of Species and Systematic Significance)
(a) (b) (c)
Figure 17. I. trita var. subulata: (a) entire seed; (b) enla rg ement of seed coat; (c) H il um shape.
(a) (b) (c)
Figure 18. I. volkens ii: (a) entire seed; (b) enlargement of seed coat; (c) H il um shape.
Ta bl e 2 . SE M obser va t i on s on seed s surface ch a racter of 18 speci es of Indigofera (L
e gum i nos ae ).
Seed s s u rface chara cter te xture
ridged r etic u late
s i mpl e compound (b i r etic ul ate )open e d
T a x a
wr i nkly groovy
i rr e gul a rr e gul a r I II III
s cale d rough
1. I. amorpho i des – – – – – + – – – –
2. I. arabi c a + – – – – – – – – –
3. I. a rgen te a – – – – + – – – – –
4. I. arr ect a – – + – – – – – – –
5. I. ar tic u l ata – – + – – – – – – –
6. I. coerul ea var. o cci denta li s – – + – – – – – – –
7. I. c o l ut e a – – – – – + – – – –
8. I. hochs tette r i – – – – – – – – – +
9. I.
i n t r ic ata – – – – – – – – + –
10. I. li ni f ol i a – + – – – – – – – –
11. I. ob l ong if o li a – – – – – + – – – –
12. I. s e ss ilifl ora – – – – – – – + – –
13. I. spi c ata – – – – + – – – – –
14. I. spin ifl ora – – – – – + – – – –
15. I. spinosa – – – + – – – – – –
16. I. ti nc t or i a – – – – – – + – – –
17. I. tri ta var. subula t a + – – – – – – – – –
18. I. v o lke ns ii +* – – – – – – – – –
Por.-Sret. = porate to simplereticulate; + = the feature present; – = the feature absent; +* = wrin kly ridged to bireticulate; I = the out e r reticulum is th in and
inn er one is thick; II = the outer r eticulum is thick and the inner one is thin; III = the outer and th e inner r et ic ulum are the s i m ila r.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia
(Identification of Species and Systematic Significance)
492
3.8. Seed Size
Seed dimensions vary greatly among the examined taxa,
the largest seeds in I. argentea have a diameter of 0.95 ×
0.12 mm, and the smallest seeds measure 0.08 × 0.09 -
0.1 mm in I. Linifolia and I. volkensii, while the rest of
the studied species have seeds their dimensions from
0.11 × 0.11 - 0.25 × 0.18 mm. The seed size was found
useful to separate species of I. argentea, I. Linifo lia and I.
volkensii from the other species (see Table 1).
3.9. Seeds Shape
The sh ape of seeds is show ed a lar ge va ria tion a mong th e
investigated taxa. Most of seeds have circular shape and
others are irregular or rectangular in shape (Table 2).
Seeds are rectangular in I. argentea, I. coerulea var.
occidentalis, I. spinosa, I. tinctoria and I. volkensii; ir-
regular in I. amorphoides, I. Arabica, I. arrecta, I. ob-
longifolia, I. spiniflora and I. trita var. subulata and cir-
cular in the rest of the studied taxa (Figures 1-18). The
shape of seeds was found useful to distinguish between
three groups in the studied Indigofera species (Figures
1-18 and Table 1).
3.10. Seeds Ornamentation
Seeds ornamentation is a significant character to separate
among studied, ornamented species of Indigofera. The
ornamentation of seeds present in some species like I.
hochstetteri, I. Linifolia, I. sessiliflora, I. spicata, I.
spiniflora, I. spinosa, I. tinctoria, I. volkensii and absent
in the others. Also ornamentation colour was found use-
ful to distinguish among the ornamented seeds. The col-
our varies from brown in I. hochstetteri and I. Linifolia,
dark brown in I. spicata and I. tinctoria , green to oily in I.
sessiliflora, purple to dark purple in I. spiniflora, oily to
dark brown in I. spinosa and finally purple to black in I.
volkensii. The ornamentation of seeds was found useful
to separate between two groups of seeds, ornamented and
not ornamented seeds. Also with ornamentation colour
we can distinguish among I. sessiliflora, I. spiniflora, I.
spinosa and I. volkensii from the others ornamented spe-
cies (Figures 1-18 and Table 1).
3.11. Character of Seeds Surface Texture
The character of Seeds surface texture can be of consid-
erable diagnostic and systematic value. The texture of
seeds surface varies from reticulate, ridged, scaled to
rough (Table 2). There are three forms of reticulation, it
may be opened, simple or compound (bireticulate).
Opened reticulate surface present in I. sessiliflora, simple
reticulate seeds surface texture may be regular or irregu-
lar, simple regular reticulate surface exists in I. spinosa,
but simple irregular reticulate surface appeared in I. ar-
recta, I. articulate and I. coerulea var. occidentalis.
Compound or bireticulate surface also has three forms, it
may be thin in the outer reticulum and thick in the inner
one, thick in the outer reticulum and thin in the inner
layer or the outer and the inner reticulum have the same
thickness, the first form present in I. argentea and I. spi-
cata, the second form present in I. amorphoides, I. co-
lutea, I. oblongifolia and I. spiniflora and the third form
are showed only in I. tinctoria. The ridged seeds surface
texture also are appeared in two froms, it may be wrinkly
ridged in I. Arabica and I. trita var. subulata, wrinkly
ridged to bireticulate in I. volkensii, or groovy ridged
only in I. linifolia. Scaled surface also are existed only in
I. intricata and rough surface is appeared only in I.
hochstetteri. It is cleared that, the texture of the seeds
surface is essential and of great importance property to
distinguish among the inv estigated taxa, it is u sed to dis-
tinguish clearly among species of I. spinosa, I. sessili-
flora, I. linifolia, I. intricate, I. tinctoria and I. hochs-
tetteri.
3.12. The Shape of Hilum
The shape of hilum among the investigated taxa showed
a large variation. Shape of hilum varies from ovate, ellip-
tic or circular in shape (Table 3). Hilu m is wide ovate in
I. amorphoi des, I. hochstetteri, I. linifolia, I. obl on gi f olia,
I. sessiliflora, I. spiniflora and I. spinosa, ovate in I. co-
erulea var. occidentalis and I. trita var. subulata, only
elliptic in I. arabica, I. articulate and I. volkensii, wide
elliptic in I. argentea, I. arrecta, I. intricata, I. spicata
and I. tincto ria, finally hilum has circular shape only in I.
colutea.
4. Discussion
From the above it can be seen that a clear cut distinction
can be made among taxa based on the main external seed
morphology. The variations observed in the seed coat
patterns at high magnification were generally species-
specific. Seeds texture characters applied to the species
of Indigofera L. in Egypt proved to be useful in the dis-
tinction between four types of which two types repre-
sented by only one species, for example, the scaled tex-
ture type was discern ed in only in I. in tricata, rough tex-
ture type was observed also only in I. hochstetteri.
Moreover, in I. arabica, I. linifolia, I. trita var. subulata
and I. volkensii species two forms of the ridged texture
type was observed, the first wrinkly ridged texture form
was showed in I. arabica, I. trita var. subulata and I.
volkensii and the second groovy ridged form are distin-
guished only in I. linifolia. The latest fourth texture type

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia 493
(Identification of Species and Systematic Significance)
Table 3. Tubular summary showing the shape of hilum in investigated species of Indigof
e ra.
T a x a wide ov ate ov ate elli pt ic wide elli pt ic ci r c ul a r
1. I. amorpho i des + – – – –
2. I. arabi c a – – + – –
3. I. a rgen te a – – – + –
4. I. arr
ect a – – – + –
5. I. ar tic u l ata – – + – –
6. I. coerul ea var. o
cci denta li s – + – – –
7. I. c o l ut e a – – – – +
8. I. hochs tette r i + – – – –
9. I. i n t r ic ata – – – + –
10. I.
li ni f ol i a + – – – –
11. I. ob l ong if o li a + – – – –
12. I. s
e ss ilifl ora + – – – –
13. I. spi c ata – – – + –
14. I. spin ifl ora + – – – –
15. I. spinosa + – – – –
16. I. ti nc t or i a – – – + –
17. I. trita var. subu la t a – + – – –
18. I.
v o lke ns ii – – + – –
+ = the featu re present; – = the f eature a bs e n t .
is the reticulate type, it was observed in three forms, the
first form is the opened reticulate texture was discovered
only in I. sessiliflora, the second one was the simple re-
ticulate texture, it may be with irregular reticulation as
shown in I. arrecta, I. articulata and I. coerulea var.
occidentalis or has regular reticulation as observed only
in I. spinosa and the third form was the compound (bi-
reticulate) reticulate texture, there are three probabilities
for the outer and the inner layers of the reticulum, in the
first probability the o uter reticulum is thick and the inner
one is thin and this was showed in both I. argentea and I.
spicata, and in the second probability the outer reticulu m
is thick and the inner one is thin and was observed in I.
amorphoides, I. colutea, I. oblongifolia and I. spiniflora,
but in the third one the outer and the inner reticulum have
the same thickness, this was showed on ly in I. tinctoria .
Fruit and Seed morphological characters were helpful
in distinguishing various species (Table 2). The smallest
seed is those of I. Linifolia (0.08 × 0.09 mm) and the
largest are those of I. argentea (0.95 × 0.12 mm). Seeds
size of other taxa ranged between (0.08 × 0.1 - 0.25 ×
0.18 mm). Seeds are more or less similar in shape being
straight, cylindrical; flat, fickle; deflexed, cylindrical;
deflexed, flat; circular; straight, angular to cu rved.
Hilum shape contributes to differentiate among th e re-
lated species of Indigofera L.; I. amorphoides, I. hoch-
stetteri, I. linifolia, I. oblong ifolia, I. sessiliflora, I. spini-
flora, I. spinosa, I. coerulea var. occidentalis and I. trita
var. subulata are characterized by ovate to wide ovate
hilum, while I. arabica, I. articulata, I. volkensii, I. ar-
gentea, I. arrecta, I. intricata, I. spicata and I. tinctoria
exhibit elliptic to wide elliptic hilum and only I. colutea
that has circular hilum.
The Constriction level of fruits also contributes to dif-
ferentiate I. articulata, I. coerulea var. occidentalis, I.
oblongifolia, I. sessiliflora, I. spiniflora and I. volkensii
species from the other investigated taxa which are char-
acterized by constricted fruits while the other taxa exhibit
even fruits. It also points to the close relatioship between
the I. Arabica, I. articulata, I. coerulea var. occidentalis,
I. Linifolia, I. sessiliflora, I. spicata and I. spiniflo ra spe-
cies which exhibit very close seeds being similar in hi-
lum position. The fruits and seeds colour is more or less
uniform in most investigated species. The seeds are cir-
cular, rectangular to irregular in shape.
In conclusion, the present study supports the use of
seed morphological characters as a parameter for species
identification. The results suggest both a close relation-
ship between different species of Indigofera L. because
there are different types of seed surfaces, seed shapes and
epidermal cells similar each other from traditional spe-
cies.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia
494 (Identification of Species and Systematic Significance)
REFERENCES
[1] B. D. Schrire, “Evolution of the Tribe Indigofereae
(Leguminosae-Papilionoideae),” In: M. D Crisp and J. J.
Doyle, Eds., Advances in Legume Systematics, Vol. 7,
1995, Royal Botanic Gardens, Kew, pp. 161-244.
[2] H. K. Airy Shaw, “A Dictiona ry of the Flowering Plants &
Ferns,” 8th Edition, Cambridge University Press, Cam-
bridge, 1985.
[3] D. J. Mabberley, “The Plant Book,” 2nd Edition, Cam-
bridge University Press, Cambridge, 1997.
[4] S. Collenette, “Wild Flowers of Saudi Arabia,” National
Commission for Wildlife Conservation and Development
(NCWCD), Riyadh, Kingdom of Saudi Arabia, 1999.
[5] S. A. Chaudhary, “Flora of the Kingdom of Saudi Arabia
(Vascular Plants), Vol. 1,” National Agriculture and Wa-
ter Research Center, National Herbarium, Ministry of
Agriculture and Water, Riyadh, Saudi Arabia, 2001.
[6] I. De Kort and G. Thijsse, “A Revision of the Genus In-
digofera (Legu minosae- Papilionoideae) in Southeast Asia,”
Blumea, Vol. 30, No. 1, 1984, pp. 89-151.
[7] P. G. Wilson and R. Rowe, “The Indigofera trita Com-
plex (Fabaceae: Indigofereae) in Australia,” Telopea, Vol.
5, No. 4, 1994, pp. 637-645.
[8] J. D. Brisson and R. L. Peterson, “A Critical Review of
the Use of Scanning Electron Microscopy in the Study of
Seed Coat,” Scanning Electron Microscopy, Vol. 2, 1976,
pp. 477-495.
[9] V. H. Heywood, “The Characteristics of the Scanning
Electron Microscope and Their Importance in Biological
Studies,” In: Scanning Electron Microscopy: Systematic
and Evolutionary Applications, The Systematics Associa-
tion Special Volume, Vol. 4, 1971, pp. 1-16.
[10] W. Barthlott, “Microstructural Features of Seed Sur-
faces,” In: V. H. Heywood and D. M. Moore, Eds., Cur-
rent Concepts in Plant Taxonomy, Academic Press, Cam-
bridge, 1984.
[11] N. R. Lersten, “Testa Topography in Leguminosae Sub-
family Papilionoidae,” Proceedings of the Iowa Academy
of Science, Vol. 88, No. 4, 1981, pp. 180-191.
[12] J. V. Suba Rao and S. R. Shannmukha Rao, “LM and
SEM Studies in Seed Morphology in Some Tephrosia
PERS. (Leguminosae),” Feddes Repertorium, Vol. 103,
No. 5-6, 1992, pp. 339-343.
[13] S. A. Chaudhary and A. A. Al-Jawaid, “Vegetation of the
Kingdom of Saudi Arabia,” Ministry of Agriculture and
Water, Kingdom of Saudi Arabia, 1999.
[14] A. M. Migahid, “Flora of Saudi Arabia,” 2nd Edition, Vol.
2, King Saud University Libraries Publication, 1989.
[15] L. Boulos, “Flora of Egypt Checklist,” Revised Anno-
tated Edition, Al-Hadara Publishing, Cairo, 2009.
[16] W. Barthlott and B. Ziegler, “Mikromorphologie der Sa-
menschalen als systematischem Markmal bei Orchideen,”
Berichte der Deutschen Botani schen Gesellschaft, Vol. 24,
1981, pp. 267-273.

Seed Morphology of Some Species of Indigofera (Fabaceae) from Saudi Arabia 495
(Identification of Species and Systematic Significance)
Key to the Studied Taxa Based on Seed Characters
1. a. Seeds surface reticulate…………………………………………………………………………...…………...……7
b. Seeds surface otherwise……………...………………………………………………………………...……………2
2. a. Seeds surface groovy ridged……………………………....................................................................……..I. linifolia
b. Seeds surface otherwise………………….…………………………………………………...……………………..3
3. a. Seeds surface scaled……………………...………………………………………………………...….......I. intricata
b. Seeds surface otherwise…………...……………………………………………………………...…………………4
4. a. Seeds surface rough……………………………………………………………………………....…….I. hochstetteri
b. Seeds surface wrinkly ridged……………..……………………………………………………………...………….5
5. a. Hilum has ovate-shaped…………………....…………………………..................................…..I. trita var. subulata
b. Hilum has elliptic-shaped…………………………………………….……...………………………...…………….6
6. a. Seeds colour gray………………………...…………………………………………………………...……I. Arabica
b. Seeds colour brown…………………….…….……………………………………………………...……..I. volkensii
7. a. Seeds surface opened reticulate…………………………………………….……………………...……I. sessiliflora
b. Seeds surface otherwise……………………...………………………………………………………...……………8
8. a. Seeds surface compound reticulate………………………………………………………………………...………..9
b. Seeds surface simple reticulate…………………………………..……………………………………...…………15
9. a. The outer and the inner reticulum are similar in thickness…………………………………………...…..I. tinctoria
b. The outer and the inner reticulum are otherwise……………………………………………………...…………....10
10. a. The outer reticulum is thin and the inner one is thick……….........…….................................................................11
b. The outer reticulum is thick and the inner one is thin………………………………….………………………….12
11. a. Seeds shape is rectangular without ornamentation…...……………………………………………...….I. argentea
b. The outer reticulum is thick and the inner one is thin………………………………….………………………….12
12. a. The hilum shape is circular…………………………………………………………………………….....I. colutea
b. The hilum shape is wide ovate…………………………………………………………………………………….13
13. a. Fruits are even………………………...…………………………………………………………….I. amorphoides
b. Fruits are deeply constricted…………………………………………………………………………...………….14
14. a. The mean of fruits length 2.2 cm…………………………………………………………………......I. oblongifolia
b. The mean of fruits length 3.5 cm……………...…………………………………………………...……I. spiniflora
15. a. Seeds surface has simple regular reticulation…………………………………………………….…….….I. spinosa
b. Seeds surface has simple irregular reticulation……………………………………………………….......……….15
16. a. The hilum shape is ovate…………...………………………………………………….I. coerulea var. occidentalis
b. The hilum shape is elliptic to wide elliptic……………………………………………………...………...………17
17. a. Fruits are even……………………………….……………………………………………………...…….I. arrecta
b. Fruits are deeply constricted…………………..……………………………………………………...….I. articulata