Kingdom Plantae - an overview (2024)

Clinical Features

The vast majority of plants are considered non-toxic (Table 158.1). However, serious toxicity can result from certain plant exposure (Table 158.2). Toxicity does not correlate well with taxonomy, and plants within the same genera may have varying toxic profiles. Further complicating matters, the severity of exposure may depend on the method of ingestion (ie, chewed or swallowed) and which part of the plant was ingested.⁴ For example, although all parts of the water hemlock plant are considered toxic, cicutoxin is most concentrated in the root of the plant. The majority of serious or fatal outcomes occur in the adult population intentionally ingesting botanicals for suicidal or recreational intent.³ A focused history and physical examination should be aimed at identifying the involved plant and any toxidrome common to botanical exposures.

8.1 Introduction

Kingdom Plantae includes numerous herbal sources that are abundant in medicinally important phytoconstituents. One such pharmacologically important genus of Plantae is Curcuma, belonging to the family Zingiberaceae. Plants belonging to Curcuma genus abound in several medicinal values, being antiallergic, anticancer, antidiabetic, anti-inflammatory, antivenom, cardioprotective, digestive stimulant, hepatoprotective, hypolipidemic, and neuroprotective (Chaturvedi et al., 2014). Numerous Curcuma species are found predominantly to be native to Asia; however, some species have been exported from their native, tropical countries (India, Indonesia, Myanmar, Thailand) and naturalized in temperate regions (Canada, Mexico, and the United States) (Wohlmuth, 2008), for exploration of their curative values.

This chapter presents a compilation of the chemical composition, occurrence, and potential health benefits of the most essential Curcuma sp. distributed across different countries. Bioefficacy of different Curcuma sp. is accredited to the various curcuminoids in them. This chapter also aims at elaborating the efficacy of curcuminoids in alleviating a number of health complications, with a special focus on curcumin isolated from Curcuma longa.

Characteristics of Wind-Pollinated Plants

By comparison to extant relatives, the most primitive vascular plants in the fossil record appeared to be wind-pollinated. Although wind pollination appears to be a simpler process than vector-facilitated pollination, it is extravagant in requiring a large amount of pollen to be produced to ensure successful reproduction. Erdtman studied numerous trees and grasses and showed that wind-pollinated plants produce extraordinary amounts of pollen.¹⁹ Each catkin may have more than 200 individual tiny flowers. He reported that a single birch catkin produced about 6 million pollen grains, and an alder catkin 4.5 million. An English oak catkin released 1.25 million grains. Erdtman then tabulated the number of catkins per tree and calculated the amount of pollen produced. A birch tree released more than 5.5 billion grains over a single year, alder 7.2 billion, and an oak less at 0.6 billion grains. Spruce also produced about 5.5 billion grains in a year. Cereal rye (Secale cereale) contained 4.25 million pollen grains per inflorescence.¹⁹

Insect pollination followed as a more efficient technique. However, certain anemophilous plants such as grasses give evidence of losing entomophilous characteristics and returning to wind pollination as a later evolutionary ploy.²⁰ Anemophilous characteristics are summarized inBox 27.1. Such plants have incomplete flowers—that is, male and female functions are found on separate structures. The pollen-producing flowers are exposed to the wind. On taller plants or trees this is frequently on dangling catkins, having hundreds of small individual flowers (Fig. 27.1). On weeds or grasses the inflorescences are thrust up into the air on the higher portions of the plant (Fig. 27.2). Female flowers may be lower, often at axils of leaves, or at stem junctions. Petals and sepals, rather than being showy, are insignificant or absent, and other attractants such as color, fragrance, or nectar are absent. The pollen grains themselves tend to be small and dry with little surface resin and with reduced ornamentation to minimize turbulence in air.

In 1930, August Thommen set out five necessary principles for a plant to be an important inducer of pollinosis (Box 27.2).²¹ Referred to as Thommen's Postulates, they continue to be generally correct, although with some caveats. The “excitant of hay fever” appears to be a protein or glycoprotein that is easily eluted on contact with water, or coated on respirable cytoplasmic particles. Although most pollinosis-inducing plants are wind pollinated, in the proper setting entomophilous plants can release sufficient airborne pollen to cause sensitization. A single point source could lead to individual sensitization. Although most pollen grains settle within meters of the source, pollens can be transported for hundreds of miles.^2,19

Introduction

The ancestors of land plants were aquatic green algae and the transition to life in terrestrial environments presented a number of challenges not least in regard to reproduction. Indeed novel reproductive structures that enhance desiccation tolerance and remove the need for water in gamete transfer are predominant characteristics in the classification of these organisms. In addition, throughout the evolution of land plants the haploid gametophyte stage of the life cycle has been progressively reduced, from being the dominant life stage in bryophytes, to only 3–9 cells in angiosperms (flowering plants). This trend towards dominance of the diploid sporophyte and reduction of the haploid gametophyte life stages is often interpreted as being an adaptation to the substantially higher levels of mutagenic UV light in terrestrial than aquatic environments, favoring diploids which inherently possess a “back-up” set of genetic material.

Neurotoxins of Plants and Fungi

Pharmacologically active agents are present in thousands of plants and fungal species. Although fatal poisoning is rare, many of the commonly encountered species are capable of inducing serious neurological symptoms. Toxicity occurs in several circ*mstances. Approximately 75% of cases occur in children younger than age 6 as a result of accidental ingestion. Adult poisoning may happen when toxic plants or mushrooms are mistaken for edible species. Another category arises with intentional consumption by those seeking drug-induced mood effects from plants such as Jimson weed.

Plant identification is difficult and should be left to a trained botanist or mycologist. Common names of plants are inadequate, and botanical names should be used whenever possible. Even without a definitive identification, the history of ingestion and recognition of a characteristic syndrome are often sufficient for a tentative diagnosis. Initial treatment is usually empirical, consisting of gastric lavage or catharsis and supportive measures. With the exception of anticholinergic poisoning, there are few specific antidotes.

A comprehensive review of the numerous botanical toxins is impossible.Table 86.1 lists several major categories and the commonly associated plants in each category. Omitted are plants that do not have direct toxicity on the nervous system, such as those containing cardiac glycosides, coumarin, oxalates, taxines, andromedotoxin, colchicine, and phytotoxins. Secondary neurological disturbances may result from these toxins because some can cause electrolyte abnormalities, cardiovascular dysfunction, or coagulopathy.

Taxonomic Diversity

Sexual Dimorphisms in Plants

Dioecy is much less prevalent in plants than in animals. Approximately 96% of species within the kingdom Plantae are flowering seed plants (angiosperms; Roskov et al., 2014) and only about 6% of angiosperm species are dioecious (Renner and Ricklefs, 1995; Barrett, 2002; Vamosi et al., 2003). Among the remaining seed plants (gymnosperms) 50% of species are dioecious, including 37% of conifers (Givnish, 1980; Bateman et al., 2011). Among spore-forming plants, dioecy is very rare in ferns (Jesson and Garnock-Jones, 2012) but relatively common in bryophytes (mosses, liverworts, and hornworts) where it occurs in 50–60% of species (Hedenas and Bisang, 2011; Jesson and Garnock-Jones, 2012; McDaniel et al., 2013).

In most dioecious plants, only reproductive structures distinguish the sexes. These consist of primary reproductive organs (e.g., the stamens and pistils of angiosperm flowers) plus surrounding somatic tissues, often formed from modified stems or leaves (e.g., the calyx and corolla of angiosperms). Sexual dimorphisms in these somatic tissues are generally interpreted as adaptations in males for dispersing pollen or sperm and in females for capturing pollen or sperm and for protecting and provisioning embryos (Givnish, 1980; Eckhart, 1999; Geber, 1999; Barrett and Hough, 2013; McDaniel et al., 2013). These are the predominant secondary sexual dimorphisms in plants, and are most pronounced in species that depend on wind or water for pollen dispersal but produce large seeds or fruit that are dispersed by animals (Givnish, 1980; Renner and Ricklefs, 1995; Vamosi et al., 2003; Biernaskie, 2010; Bateman et al., 2011).

The secondary sexual trait most likely to differ between male and female reproductive structures is size. Flower size dimorphisms occur in more than 80% of diecious angiosperm species, with male flowers somewhat more likely to be larger than the reverse (Eckhart, 1999). In contrast, in dioecious gymnosperms the female reproductive organs (strobili) are larger and only the female strobili develop into the large, long-lived cones typical of conifers and cycads. In angiosperms, the number of flowers and the sizes of inflorescences (flower clusters) may also differ between sexes, with males more commonly having more flowers or larger flower clusters than females. In a few families, differences in flower shape and in the position or orientation of the flowers on the plant have also been described (Eckhart, 1999; Barrett and Hough, 2013).

Other than reproductive structures, the most prevalent SDM in plants is overall size. In both angiosperms and gymnosperms, males tend to be larger than females in large, long-lived, woody species (e.g., trees and shrubs), whereas females tend to be larger in small, short-lived, herbaceous species (Obeso, 2002; Barrett and Hough, 2013). Size dimorphism is most extreme in pleurocarpous mosses (class Bryophyta) where, in about a third of species, dwarf males develop from spores that land on the stems or leaves of females and remain attached to the female throughout their lives (Hedenas and Bisang, 2011).

Sexual dimorphisms in other aspects of plant vegetative morphology are much less common but have been noted in at least a few species. Examples include leaf size (females more commonly larger), leaf shape, stem size (females more commonly thicker), and branching architecture (males usually more branched) (Dawson and Geber, 1999; Kavanagh et al., 2011; Barrett and Hough, 2013). As in animals, male and female plants also often differ in ecological and life-history traits (Dudley, 2006; Geber et al., 1999; Barrett and Hough, 2013). The sexes are sometimes partially segregated by habitat, with females more restricted to sites with more water or nutrients, and males often exceed females in their capacity for clonal reproduction, reproduce at an earlier age, and senesce earlier than females. These differences reflect sex-specific trade-offs between growth and reproduction and, as in animals, are interpreted as adaptations for maximizing fitness through male or female reproductive functions.

Algae, Fungi, and Plants

A single Code (McNeill et al., 2012) covers algae, fungi, and plants; the organisms traditionally studied by botanists even though many are no longer classified in the plant kingdom (Plantae). It consequently embraces cyanobacteria (Bacteria), fungi (Fungi), slime-molds (Protozoa), and various algal groups (Chromista, Heterokonta, or Straminipila). The name of this Code was changed from the International Code of Botanical Nomenclature in July 2011 to reflect the disparate organisms it covers.

The nomenclature of these groups is considered as starting from the publication of Linnaeus’ Species Plantarum in 1753, but the first internationally agreed Code dates from the Lois de La Nomendatue Botanique prepared by Alphonse de Candolle in 1867 and adopted by the International Botanical Congress in Paris that year. Later starting dates, all linked to particular major publications by authors other than Linnaeus are used for some groups, notably mosses (1801), certain groups of algae (1848–1900), and fossils (1820). Fungal names were formerly dated from 1801 or 1821, depending on the group, but that practice was discontinued in 1981. Names of fungi accepted in the previous starting point works by Christian Persoon (1801) and Elias Fries (1821–1832) remain sanctioned for continued use even if earlier competing names exist. Traditionally, the distribution of hard-copy publications, i.e. books or journals, was required for effective publication under the Code. However, this situation changed. From 1st January 2012, electronic publications are accepted as a means of effective publication, provided that certain criteria are met. The work must have an ISBN or ISSN number, as appropriate, and be in its final form and archived. Articles in journals that are made available online and in an unalterable form prior to distribution of printed copies are now considered effectively published and date from the date on which the online version was published.

In addition to the insertion of terms to denote ranks below species and differences in the practice of how describing authors are cited, several features of this Code are unique to it. New scientific names published after 1935 and before 1st January 2012 must, with a few special exceptions, have a description or diagnosis (i.e., a statement of how the organism differs from others) in Latin. However, on or after 1st January 2012, the validating diagnosis or description must be in either English or Latin.

This Code recognizes the priority of names only within the particular rank under consideration. This means, for example, that even if a plant was recognized as a subspecies or variety long before a species name was coined, the species name is nevertheless the one to be used. In addition, this Code rules as illegitimate names that have been introduced unnecessarily when another should have been adopted by the author, for instance, by placing an earlier validly published name as a synonym when it was introduced. Also illegitimate are names spelled in either exactly the same way or are so similar in spelling that they are likely to be confused; these names are termed “hom*onyms”, and only the oldest is generally available for use. For example, Erica hibernica (Hook and Arnott) Syme 1866 is illegitimate and to be rejected because of the existence of Eri. hibernica Utinet 1839, which represents a different species and is based on a separate name-bearing type. That Syme's name was based on Eri. mediterranea var. hibernica Hook and Arnott 1835 does not affect the situation, as that name has priority from 1835 only in the rank of variety and not of species.

Name-bearing types have had to be designated when describing new species and infraspecific taxa in this Code since 1958, and from 1990 the institution where they are preserved must also be cited. Living type material is not permitted, but dating from 1993 freeze-dried (lyophilized) material or specimens of algae or fungi preserved in liquid nitrogen are acceptable provided they are maintained in a metabolically inactive state; resuscitated cultures from such material are then referred to as ex-holotype, ex-isotype, etc.

This Code has special provisions for hybrids, fungi and fossils, which are considered separately below (see Special Cases). Appendices listing conserved and rejected names, and suppressed publications form a part of the Code, but at the International Botanical Congress in Melbourne in 2011, it was decided that the appendices need not be printed in the Code itself but could be published separately. The provisions of this Code are debated at each 6-yearly International Botanical Congress, after which a new edition of the Code is issued. Any changes proposed have to be published, something generally done in the journal Taxon, are balloted on first by mail (by individual members of the International Association for Plant Taxonomy), and then at the Nomenclature Section meeting of the Congress itself, where a 60% majority is normally required to effect any change. The Congress establishes a series of permanent Committees that are charged with considering and making recommendations on proposals to reject or conserve names in different groups; those are also generally published in Taxon and are ratified by the subsequent Congress.

New proposals to be placed before the next Congress in 2011 include ones to permit electronic-only publication under particular circ*mstances, a move from mandatory Latin diagnoses (see above), the transfer of decision making in relation to matters concerning fungi to International Mycological Congresses (now organized every 4 years under the auspices of the International Mycological Association), and to require the prior deposit of key nomenclatural information in a recognized online repository (currently MycoBank) for the valid publication of fungal names.

5.3 Botanical Classification of Rhodiola sp.

The taxonomical status of the genus Rhodiola is quite complex. Before World War II, taxonomists distinguished between different species of Rhodiola as independent genus (Hegi, 1963). Later, different researchers classified Rhodiola as subgenus, then again as a genus and so on. Because of morphological similarities, the classification of plants under this genus still remains a daunting task. Ghiorghita et al. (2015) detailed the systematic classification of Rhodiola sp.: Kingdom: Plantae; Phylum: Magnoliophyta; Class: Magnoliopsida; Order: Rosales; Family: Crassulaceae; Genus: Rhodiola; Species: 96 or more.

As mentioned in Section 5.2, majority of studies under genus Rhodiola are being conducted on R. rosea. This species approximately covers 51% of all animal studies and 94% of all human studies conducted. R. rosea has been found to be toxicologically safe for both animals and humans. This species is prevalent in three continents: Asia, Europe, and North America (Table 5.1). In general, R. rosea is a perennial, succulent herb with acylindrical or oblong, thick (diameter: 0.5–2.5cm), fleshy and fragrant (characteristic rose) rhizome. Leaves are pale green in color, ovate or oblong (1–5cm×0.4–1.5cm), fleshy and glabrous. Leaf margin is entire or dentate. The plants are dioecious. The species is diploid (2n=22).

Similar to R. rosea, R. imbricate is a succulent herb with a thick rhizome (10–35cm), golden outside, pink inside; leaves 1.3–3cm long, oblong to narrow, margins nearly entire; flowers pale yellow in congested cluster, surrounded by an involucre of leaves (Chaurasia et al., 2007).

Vertebrate Classification