Macromorphological Revision of Indigofera L. (Faboideae, Fabaceae) in Egypt

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micromorphological traits like seed coat sculpture and the characteristics of the leaf epidermal cells, have the most significant systematic value.However, her study did not update the morphological descriptions of the genus Indigofera in Egypt.Thus, the current study aims to employ the macro and micromorphological characteristics in updating the descriptions of the Egyptian Indigofera and update their identification key as well.

Methods For Morphological Studies: Macro-Morphological Characters:
The macro-morphological characteristics of the species under study, including their leaves, stems, inflorescences, floral components, and fruits were examined using a Ray Wild stereomicroscope.The dried plant material was either examined immediately or placed in heated lactic acid for 1-2 minutes before examination.Dimensions of the leaves, petioles, and stipules were measured by using a ruler.In contrast, the floral components (epicalyx, calyx lobes, corolla, staminal tube, stamens, and styles) and the fruits were measured using ImageJ v1.45 (Schneider et al., 2012).A total of 58 plant samples from 13 taxa of Indigofera were described.The conservation status of the studied taxa in Egypt was assessed according to the International Union for Conservation (IUCN, 2022).Macrophotography was performed with a Nikon D600 digital camera (Nikon Inc., Japan).

Figures: 1.5 Distribution:
Local: Very rare, The Red Sea coastal region.

Distribution:
Local: Very rare, The Oases of the Libyan desert (Uweinat), Gebel Elba, and surrounding mountains are situated in the southeast corner of Egypt at the Sudan frontier.

Distribution:
Local: Rare, the Arabian desert East of the Nile, The Red Sea coastal region, Gebel Elba, and surrounding mountains, situated in the southeast corner of Egypt at the Sudan frontier.

Habitat:
In Egypt, Indigofera subulata var.subulata is found on rocky slopes.Conservation status: Indigofera subulata var.subulata has not been assessed for The IUCN Red List of Threatened Species.However, the species has been reported as rare in Egypt.Specimens Examined: EGYPT. Aswan Governorate, Kom Ombo, 6 February 1975, El Hadidi s.n. (CAI).
All the studied taxa are herb, undershrub, or shrub with annual and perennial duration.However, I. spinosa can be delimited from the rest of the species by having a small, spiny shrub.Stems are morphologically crucial in distinguishing between the studied species.The stem is primarily erect but becomes erect with spreading branched in I. oblongifolia, ascending in I. argentea and I. sessiliflora, ascending to sprawling in I. spiniflora and prostrate in I. cordifolia and I. hochstetteri.
Within the studied taxa of Indigofera, the plants' vegetative and reproductive parts are covered with different types of trichomes, forming an indumentum of variable density and texture.This present study revealed two morphotypes of non-glandular trichomes: unbranched (simple trichomes with four subtypes) and branched (uniseriate macroform twoarmed with six subtypes and three-armed trichomes).Of all non-glandular trichomes observed, the most prevalent type was uniseriate macroform two-armed trichomes, which appeared in all the studied taxa.Some authors have already pointed out this (Prabhakar et al., 1985;Lievens, 1992;Quesada, 1997;Sengsai et al., 2014;Osman, 2012;Badry, 2015;Shokirovna, 2023).Four types of glandular trichomes appear (filiform with three subtypes, filiform-clavate with three subtypes, clavate with seven subtypes, and peltate trichomes).Of all glandular trichomes observed, the most familiar type is clavate glandular trichomes.It was the only glandular type that appeared in the vegetative and reproductive parts, whereas the rest appeared only in the reproductive parts.This type of glandular trichomes was also reported in Indigofera by (Schrire, 1995;Quesada, 1997;Wilson et al., 2008).
In the current study, the leaf characters proved helpful in the distinction among specific taxa.There are two types of leaves: simple leaves, which distinguish only I .
cordifolia, and pinnately compound leaves, which characterize the rest of the studied taxa.One morphological feature differentiating I. coerulea var.coerulea from the other taxa is the absence of stipules.The familiar shape of stipules is subulate, but I. hochstetteri has a filiform shape, and I. cordifolia has a setaceous shape.I. subulata var.subulata has the longest stipules (2-4) mm, while I. articulata and I. spiniflora have the shortest stipules ca.1 mm.Petiole length is beneficial in distinguishing I. articulata, which has the longest petiole (5-16) mm, and I. cordifolia, which has the shortest petiole, ca. 5 mm.Within the studied taxa, leaf rachis ranges from very short ca.1mm in I. spiniflora, I. spinosa, and I trita to very long (10-45) mm in I. articulata.The most popular shape of the blade is obovate with an acute leaf base, but within a species, the variation is always between narrower limits.I. cordifolia can be separated from the other taxa by having a cordate leaf base.Leaf apex varies from acute, obtuse, retuse, or mucronate among the studied taxa.The margin is always entire.The lateral leaflets are primarily opposite and alternate in only I. oblongifolia and I. sessiliflora (Table. 1).
Most of the studied taxa flowers are born in axillary pedunculate racemes, while I. cordifolia and I. sessiliflora can be delimited from the other taxa by flowers in axillary clusters.This result is consistent with (Chauhan et al., 2015).I. trita is distinguished by the longest peduncle (30-125) mm, while I. hochstetteri has the shortest peduncle (6 -13) mm.
The calyx is campanulate with five teeth.The studied characters of the calyx teeth (shape, size, and indumentum) have significant taxonomic importance.The shape of calyx teeth among the studied taxa exhibits substantial differences.The teeth are narrowly subulate in I. cordifolia, narrowly subulate-filiform in I. hochstetteri, subulate in I. arabica, I. colutea and I. spinosa, narrowly triangular in I. argentea, triangular in I. articulata I. coerulea var.coerulea and I. trita, finally setaceous in I. sessiliflora.The calyx length ranges from 1 mm in I. argentea to 4 mm in I. cordifolia.
Corolla is papilionaceous and usually bright red to red.Within Indigofera, the shape and size of (standard, wings, and keel) show significant variation among the species.The shape of the standard is orbicular with a truncated base and rounded apex in most of the studied taxa.However, I. cordifolia is marked by a spathulate shape, While I. argentea and I. sessiliflora are distinguished by broadly ovate shape.The size of the standard ranges from 2 × 2 mm in I. sessiliflora to 4 × 4 mm in I. trita.The most popular shape of wings is spathulate with a truncate base and acute to obtuse apex.However, I. cordifolia can be separated from the other taxa by linear shape; I. coerulea var.coerulea, I. colutea, and I. sessiliflora are distinguished by oblong shape.The size of the standard ranges from 2 × 1 mm in I. var.coerulea, I. colutea, I. oblongifolia, and I. sessiliflora to (4 × 1) mm in I. trita.Keel size can be used as a supportive taxonomic where it ranges from (2 × 2) mm in I. oblongifolia to (4 × 4) mm in I. trita.
Stamens are diadelphous (9 + 1), in which the vexillary filament is free, and the other 9 filaments are connate.The length of the staminal tube also can be used to delimit between the studied species.I. argentea, I. hochstetteri and I. sessiliflora have the shortest staminal tube (2 mm) While I. oblongifolia has the highest staminal tube (4 mm) (Table 2).
In the current study, the variability in fruit characters (shape, length, width, and color) has proved to be helpful in recognizing specific taxa of the Egyptian Indigofera.Within the studied species, the color of the pod varies from olive to brown.The typical shape of a pod is straight cylindrical but can be curved cylindrical in I. coerulea and I. hochstetteri.The longest observed pod is 30.34 mm in I. trita, while the shortest is 4.59 mm in I. cordifolia, the broadest is 3.88 mm in I. articulata and the narrowest is 1.29 mm in I. colutea.The number of seeds per pod is usually 2-12, but it can be as low as 1-2 seeded in I. cordifolia and 1-3 seeded in I. articulata.
Seeds of flowering plants exhibit significant variation in their features.In the present study, the color of the seed varies from olive to dark brown, but I. colutea, I. cordifolia, I. hochstetteri, and I. spinosa can be separated from the other taxa by having black spots.The shape of seeds showed a considerable variation among the investigated taxa.Most seeds have a rectangular shape, but an oblong shape corresponds to I. subulata var.subulata.The spherical shape corresponds to I. colutea, I. arabica, I. articulata, I. sessiliflora, and I. spinosa.Seed size varies significantly among the examined taxa; the giant seeds in I. coerulea have a diameter of 2.37 × 2.38 mm, and the smallest seeds measure 0.75 × 0.68 mm in I. colutea.These findings agree with (Hosni, 2000;Al-Ghamdi, 2011;Elkordy et al., 2022) (Table 3).

Figures
Rare, The Nile Delta, including Cairo but not further south, The Nile Valley, from Cairo to Wadi Halfa, The Oases of the Libyan desert, The part of the Arabian desert from Qena-Qosseir Road south-wards to the Sudan boundary.(mer.stands for meridional, South), The Red Sea coastal region, Gebel Elba, and surrounding mountains are situated in the southeast corner of Egypt at the Sudan frontier.
Very rare, the part of the Arabian Desert from Qena-Qosseir Road south-wards to the Sudan boundary.(Mer.stands for meridional, South), Gebel Elba and surrounding mountains are situated in the southeast corner of Egypt at the Sudan frontier.
Rare, The Nile Valley, from Cairo to Wadi Halfa, The Oases of the Libyan Desert, Gebel Elba, and surrounding mountains, situated in the southeast corner of Egypt at the Sudan frontier.

Table 1 :
Macro-morphological characters of stipules, petioles and leaves in in the studied taxa; measurements (Minimum-Maximum).