*Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*

the tropical rainforest region is hot and wet throughout the year. The mean annual temperature is 27°C while the mean total annual rainfall is 2000 mm. The rainforest is characterized by dense and stratified vegetation, comprising various broad-leaved tree species sandwiched by lianas and herbaceous climbers. The rain forest covers Oyo, Edo, Delta, Imo, Cross River, Ogun, Ondo, and Rivers state, while the swarm forest is situated across the Niger Delta region. Parasitic plants are very much represented in the Nigerian rainforest. The largest parasitic tree, *Okoubaka aubrevillei*, is found here. It is believed to parasitize neighboring trees as an adaptive mechanism for creating light spaces in the normally thick rain forest environment. A recent report indicates that the parasitic tree is currently facing a decline in its Population due to forest degradation. Consequently, further isolating the few remnants stands in some forest areas of Edo, Cross River, and Osun States. Another interesting parasitic species found in the Nigerian rain forest is the ground-dwelling, herbaceous plant- *Thonningia sanguinea*, commonly refer to as 'ground pineapple' because they bear morphological similarities. The plant shows a special preference for native host trees such as *Guarea cedrata*, *Lophira alata Musanga cecropioides Myrianthus arboreus*, and *Ricinodendron heudelotii*, and few exotics like *Hevea brasiliensis* and *Theobroma cacao*. It is mostly found growing along forest trails, indicating its preference for disturbed parts of the forest environment. Notable members of the Loranthaceae family like *Agelanthus brunneus*, *A. dodoneifolius, Englerina gabonensis, Globimetula braunii, Helixanthera mannii, Phragmanthera capitata*, *P. kamerunensis, P. talbotiorum,* and *Tapinanthus bangwensis* are present in the luxuriant vegetation of the rain forest, attached on the branches of host trees*.* Other stem parasites like *Cassytha filiformis* and *Cuscuta australis* have a widespread distribution spanning rainforest and the savanna. Parasitic members of the Orobanchaceae scarcely sighted, only represented in this zone by *Alectra sessiliflora var. monticola.* **Table 2** shows potential distribution and host species of common parasitic plants of Nigeria.

## **4. Systematic presentation of parasitic angiosperm in Nigeria**

#### **4.1 PIPERALES:** *hydnora abyssinica* **(Hydnoraceae)**

Members of the genus *Hydnora* are subterranean, holoparasitic, and lack leaves or scales [19]. Several species of *Hydnora* have been recognized *H. africana* Thunb., *H. esculenta* Jum. & H. Perrier, *H. johannis* Becc. and *H. triceps* Drege & Meyer as distinct species; however, The family-Hydnoraceae is represented in Nigeria by *Hydnora abyssinica* A. Braun [11]. The first and only report of its existence was around Nekong, Wusali ward, a lowland area in the Sudan-savanna zone in Kanke Local Government Area, Plateau State, Nigeria [11]. *Hydnora abyssinica* is a perennial herb composed entirely of roots with extremely reduced vegetative morphology. It only emerges above ground when fruiting or flowering. *H*. *abyssinica* grows in a semiarid environment. The adaptation for such an environment might be related to the fact that water availability affects flower growth, including perianth splitting [29]. The flowers of *H. abyssinica* are protogynous; however, both cross and self-pollination can occur. Carrion flies and dermestid beetles carry out pollination. Generally, *Hydnora* species use a system similar to the pitcher traps of Carnivorous plants by trapping insects that fall into the flower tube, ensuring they do not escape [25].

#### **4.2 LAURALES:** *cassytha filiformis* **(Lauraceae)**

The genus *Cassytha* consists of about 17 species globally, with *Cassytha filiformis* being the predominant species in Nigeria. *Cassytha filiformis* is a perennial, leafless *Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*

twining plant with a stem turning clockwise around the support plant [30]. It is less selective in terms of the choice of the host; hence any plant may be used as a host [29]. Stems are green to orange, filiform, and glabrous. Leaves are reduced to minute scales, ca. 1 mm long, easiest seen near tips of stems. Flowers are sessile and few in spicate inflorescences 1(−2) cm long, each subtended by an ovate bract and two ovate bracteoles. The inflorescence is a short raceme or spike. *C. filiformis* produces false fruits enclosed in the accrescent floral tube; dried floral parts persist in the fruiting stage. Information regarding the pollination biology in *Cassytha filiformis* is scanty. However, the floral characteristics point to wind pollination, while on the other, the presence of gland in the flowers point to insect pollination. Birds disperse fruits. Bush fire has been reported to promote the germination of *Cassytha* seeds [29].

#### **4.3 SANTALALES: nigerian loranthaceae**

Loranthaceae is the largest family in Santalales with about 73 genera and over 900 species [29]. It has a wide distribution particularly in the southern hemisphere, including both subtropical and tropical areas. Members of Loranthaceae have mostly stemmed parasites, with exception of a few root parasites. They possess both primary and secondary haustoria. Loranthaceae leaves are usually evergreen, leathery, and simple with smooth edges but variable forms, from broad flat leaves to cylindrical succulent leaves. Flowers are nearly always bisexual, with 4–7 perianth members who normally are of the same color. Stamens occur in the same number as the perianth parts, but there is only one pistil. Insects and birds, especially sunbirds pollinate flowers. The fruits are berry-like, single-seeded and of different color depending on species. Birds are the main disperser. The family- Loranthaceae is represented in Nigeria by *Agelanthus brunneus* (Engl.) Balle & Halle, *Agelanthus dodoneifolius, Englerina gabonensis* (Engl.) Balle, *Globimetula cupulata* (DC.) Van Tiegh, *Globimetula oreophila* (Oliv.) Danser, *Helixanthera mannii* (Oliv.) Danser, *Helixanthera spathulata* Wiens & Polh. *Phragmanthera capitata* (Spreng.) Balle, *Phragmanthera kamerunensis* (Engl*.*) Balle, *Phragmanthera nigritana* (Hook*.* f*.* ex Benth*.*) Balle, *Phragmanthera talbotiorum* (Sprague) Balle, *Tapinanthus bangwensis (Engk. & K. Krause) Danser, Tapinanthus cordifolius*, *Tapinanthus globiferous* (A. Rich.) Tiegh, *Tapinanthus pentagonia* (DC.)Van Tiegh, and *Tapinanthus preussii* (**Figure 1**). Generally, these representative species are distributed into two main groups distinguished by the flower bracts, the Tapinanthoid and the Taxilloid group.

The Tapinanthoid group has simple to branched hairs. There are three flower types in this group. Some possess relatively small, non-explosive flowers, which are mostly adapted to pollination by insects. They are considered primitive for example is *Helixanthera mannii*, *H. spathulata.* Others like *Agelanthus* and *Englerina* have explosive flowers, and their corolla is vented. Corolla venting occurs when there is a split in the corolla and the number of splits corresponding to the number of fused petals below the corolla tip. *Agelanthus* is the most species-rich Loranthaceae in Africa. It flowers all year-round depending on the host species and the location, usually much more abundant during the rainy period. *Englerina* is mostly shrubs up to 2 m in size. The flowers are clustered in pedunculate umbels and often standing erect from horizontal branches. The corolla tube is relatively short, adapted to pollination by short-beaked birds. The opening mechanism of the flower with the obvious vents serves as signals to the pollinators that the bud is mature. *Tapinanthus* and *Globimetula.* are non-vented but explosive. The flowers explode without opening first by splits. *Tapinanthus* is a common genus in Nigeria. They are characteristically known to have a swollen tip of the corolla in the bud stage. The tip often has a color

#### **Figure 1.**

*Some common parasitic plants of Nigeria (A) male inflorescence of* Thonningia sanguinea*, (B) flowers of* Globimetula braunnii *(C) and (D)* Tapinanthus globiferus Syn. Agelanthus dodoneifolius, *(E)* Tapinanthus dodoneifolius, *(F)* Cuscuta camprestris, *(G)* Striga gesnerioides*, (H)* Striga asiatica*, (I) fruits of* Tapinanthus *sp., (J) leaves and inflorescence of* Tapinanthus bangwensis, *(K)* Hydnora *infloresence, (L) a sapling of* Okoubaka aubrevillei.

*Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*

different from the rest of the corolla and becomes darker as the bud matures. Such a dark color also serves as a signal to the pollinators that the bud is mature. It flowers all year-round depending on the host species and the location, for usually much more abundant during the dry period. *Globimetula* species are known to have just a primary haustorium. The buds have a prominent swelling at the tip like *Tapinanthus*.

The Taxilloid group has stellate hairs and has a flower that is both explosive and vented. Example *Phragmanthera,* which is the largest genus in this group. It has a large single primary haustorium. Several species of this genus are considered pests in plantations.

#### **4.4 SANTALALES:** *okoubaka aubrevillei* **(Santalaceae)**

*Okoubaka aubrevillei* is a rare tree endemic to West Africa (**Figure 1**). It is the largest parasitic plant and also produces the largest seeds known for any hemiparasite. It is a monoecious, deciduous tree that grows up to 40 m high [31]. The tree is thought to be useful for various folk medicinal purposes by different ethnic groups in all of its native ranges [21]. *Okoubaka aubrevillei* is perhaps one of the most controversial plants in Africa in terms of taxonomy and ethnobotanical information. It is believed that no tree grows within 80 feet of a 60 feet *Okoubaka* tree, except for *Myrianthus arborea, Musanga cecropoides, Cola attiensis* [31]. Its presence has been confirmed in three state locations in Nigeria: Edo, Cross River, and Osun States [32]. As exercised by *Okoubaka aubrevillei*, parasitism might be for nutritional purposes and as a means of competition for light since it dwells only in a rainforest habitat.

The leaf blade is ovate to oblong, simple and entire in shape, arranged in an alternate to almost opposite. Flowers are green in color and arranged on spines around older branches. Flowers are green in color. Unisexual flowers are present, with the female flowers slightly larger than male flowers [33]. The flowers develop into hard, yellow-colored ellipsoid drupes containing a single large seed that weighs up to 100 g. The tree is monoecious. Hence, it is expected that the plant undergoes self-fertilization (allautogamy), leading to genetic stability. Although little is known about the pollination biology, the pollination type is likely either by ants (myrmecophily) or bats (cheiropterophily) due to the small greenish flowers that preclude its chances of being pollinated by birds [32]. Seeds are speculated to be dispersed by large forest animals such as elephants.

#### **4.5 SANTALALES:** *viscum* **spp. (Santalaceae)**

*Viscum congolense* De Wild*.* And *Viscum decurrens* (Engl.) Bak. & Sprague are two representative species of the family in Nigeria. Reports on these species, particularly, *Viscum decurrens* are scanty. V. *congolense* is a dioecious, globose shrub that grows up to 50 cm tall and is found in humid forests, secondary forests, and plantation forests. Leaves are variable, elliptic-oblong in shape. The fruits are small, smooth and greenish-white in color [12].

#### **4.6 Santalales:** *thonningia sanguinea* (**Balanophoraceae)**

*Thonningia sanguinea* Vahl (Balanophoraceae) is a monotypic, rare, cryptic obligate holoparasitic plant endemic to tropical Africa (**Figure 1**). Its distribution is restricted to the forest environment, where it parasitizes forest trees [27, 28]. *Thonningia sanguinea* is a fleshy dioecious herb growing from an underground tuber. It is parasitic on other plants via its tuber. The branching yellow tuber extends horizontally up to 10 or 15 centimeters through the soil. It forms bulb-like swellings at the points where it attaches to the roots of its host plants which could either be

exotic or native species. These swellings, or galls, can reach over 18 centimeters wide [34]. The stem is coated with spirals of scale-like leaves. The leaves lack chlorophyll, as the plant obtains nutrients from hosts and does not need to photosynthesize. The flowering stem emerges from the ground to produce a bright red or pink inflorescence containing male and female flowers. The crowded flower heads are covered in scales. The inflorescence is up to 15 to 20 centimeters long [34]. Studies on its reproductive phenology suggest that *T. sanguinea* flowers all year round. The ant *Technomyrmex* species are the most common floral visitors, and it is hypothesized to be the pollinating agent [27, 28].

### **4.7 LAMIALES:** *alectra* **spp. (Orobanchaceae)**

*Alectra* is also known as the yellow witchweed. Representative species in Nigeria include *Alectra sessiliflora var. monticola, Alectra sessiliflora var. senegalensis, and Alectra vogelii Benth.* Generally, *Alectra* grows erect, emerging from a small bulb (haustorium) attached to the root of the root plant. The leaves are lanceolate, simple, subsessile, and arranged in an opposite or alternate pattern. Flowers are borne by a short peduncle and yellow in color. The fruit is a globular dehiscent capsule containing many seeds. At maturity, it opens in 2 valves. The seeds are tiny and ovoid. Seeds are dispersed mainly by wind. *Alectra* species, particularly *Alectra sessiliflora* var*. senegalensis,* are a serious threat to agriculture since they can use members of Papilionoideae such as cowpeas, peanuts, soybeans and other legumes as host.

#### **4.8 Lamiales:** *striga* **spp. (Orobanchaceae)**

*Striga*, often refer to as 'witchweed' because several species, despite their beauty, seem to perform "evil magic" like a witch. *Striga* is most common in semi-dry vegetation. *Striga* species are annuals or rarely perennials. Representative species in Nigeria include; *Striga asiatica* (Linn.) O. Ktze*, Striga aspera* (Willd.) *Benth, Striga gesnerioides* (Willd.) Vatke, *Striga hermonthica* (Del.) Benth*.*

The life-cycle of *Striga* spp. is quite complex [48]. It begins a long period of seed dormancy that could persist for up to after which the seeds then need sufficiently warm and humid conditions for one to two weeks to enter into a condition in which they can germinate (pre-conditioning). Subsequently, they need host-derived signals that stimulate germination [25]. After germination, a special organ, called the haustorium, through which nutrient materials are siphoned from the host [25]. The above-ground part of the parasite emerges after haustorium development and proper attachment to the host. This is accompanied by flower bloom, pollination, and subsequently shedding the seeds as the capsules ripen. Pollination is by insects, probably butterflies; the seeds are tiny, produced in vast numbers and dispersed mainly by wind, but also stick with mud to hoofed and clover-trotted mammals [17].

#### **4.9 SOLANALES:** *cuscuta australis* **R.Br. (Convulvulaceae)**

*Cuscuta*, commonly referred to as dodder, is the only parasitic genus in Convolvulaceae, belonging to the order, Solanales. The species is represented in Nigeria by *Cuscuta australis*. *Cuscuta* spp. bear a close similarity to *Cassytha* in appearance. However, some notable differences include that most *Cuscuta* spp. are annuals, unlike *Cassytha*, a perennial herb. Also, while *Cassytha* is a hemiparasite, *Cuscuta* is holoparasitic. Also, *Cuscuta* is a more advanced parasite than *Cassytha* due to the presence of a direct phloem contact [16].

*Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*

*Cuscuta australis* possess tiny, stalk or sessile flowers that are clustered in dense heads. Flowers are pollinated by insects; however, birds are responsible for seed dispersal [29].

## **5. Ethnobotanical relevance of parasitic plants**

The term Ethnobotany was first used by Harshberger [35] to denote the study of plants used by primitive aboriginal people subsequently; different workers have defined the subject, greatly enlarged the scope and accepted it as an interdisciplinary science for a holistic approach to man–plant relationship, hence different definitions of the concept of ethnobotany exist. Allem, [36] defined the concept as the biological, economic and cultural inter-relationship between people and plants in the environment where they exist. Schultes and Raffauf [37] broadly defined the subject as human evaluation and manipulation of plant materials, substances and phenomena in societies. Jain [38] related it to the study of how people make use of plants. According to Pushpangadan and Kumar [39], it is the entire realm of useful relationship between plant and humans. These definitions point out a relationship between people of a given community or society, the environment and the plant diversity in that particular community.

Ethnobotany has now been recognized as an integral part of indigenous/local knowledge of a particular society. Thus, different societies or communities have their own knowledge about plants and their uses. Indigenous knowledge represents an immense valuable database that provides humanity with an insight into how numerous communities have interacted with the changing environment, providing local solutions for local problems and suitable ways for coping with challenges posed by specific conditions. According to Warren and Cashman [40], ethnobotanical knowledge is how most communities survived for centuries by adapting themselves to their environment, using their intrinsic knowledge of associated resource management.

Parasitic plants are keystone species in plant communities, exhibiting a unique and important ecological role [3]. They are common in many natural and seminatural ecosystems, from tropical rain forests to the savanna. Although some parasitic plant species are important pests of human agriculture and forestry, many are highly valued for food and wood as well as for their medicinal and esthetic properties [8].

The study and management of parasites have historically focused on the control, and even elimination, of parasite populations, for example, researchers have intensified efforts to eradicate several mistletoe species, *Cuscuta*: *Striga*, and broomrapes which attack food crops [35]. Despite this ecological and economic importance, parasitic plants have often been overlooked and excluded from most ethnobotanical checklist and flora assessment surveys [8]. Literature survey reveals that only in few instances have parasitic plants been recognized for their ethnobotanical value [41, 42].

The importance of indigenous knowledge is overwhelming especially with regard to parasitic plants. Aiyeloja and Bello [43] valued it as the sum of the experience that forms the basis for decision making for familiar and unfamiliar problems and challenges in a local community. The overall ethnobotanical uses of parasitic plants are quite high. However, the traditional knowledge of these plants have been widely threatened by current trends of economic globalization that promote intensive agriculture, industrialization, and the migration of rural populations to urban areas. Consequently, it is crucial to record this fast-disappearing knowledge before it is lost along with the present generation of elderly persons. **Table 3** shows the ehnobotanical relevance of parasitic plants.


*Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*


#### **Table 3.**

*Ethnobotanical relevance of parasitic plants.*
