Tropical Plant Systematics

Today I have another piece from one of my final exams, this one is from PBIO 241: Tropical Plant Systematics, which has been one of my favorite courses at UVM to date. For our final, we had the choice to answer two of four questions in essay format. This post is answering one of those questions that I chose, which is giving a full discussion on one of the families we did not cover in the class (we made it through 22) but is prominent in the tropics and has some fun characteristics. I chose the “four o-clock family” or Nyctaginaceae. Most of the information is from my class notes from PBIO 241 and from the lecture slides by Dave Barrington for this class. If the source is not cited, the information is likely from what I learned in class or is my own reasoning. The last part of this post contains my work cited. I hope you find this interesting and learn something new! A Synopsis of a Second-Level Family: Nyctaginaceae

Common Name: “Four o’clock Family”

Phylogeny: This family is found among the Core Eudicots, in the order Caryophyllales. It’s separated from Cactaceae, the other family in the Caryophyllales we looked at in this course, by a fair amount. The next closest relatives are Sarcobataceae, Gisekiaceae, and Phytolaccaceae.

Tree from the Angiosperm Phylogeny Website.

Tree from Douglas and Manos 2007 shows a phylogenetic tree of most of the genera of Nyctaginaceae in North America .

The family Nyctaginaceae is made up of 34 genera with 350 species. There are seven subgroups:

1. Caribeeae

2. Leucastereae

3. Boldoeae

4. Colignonieae

5. Nyctagineae

6. Bougainvilleeae

7. Pisonieae

Local Nyctaginaceae: Plants of this family found in Vermont include Mirabilis jalapa, M. hirsuta, M. albida, M. nyctaginea, and M. linearis.

Asterid Characters: This family is part of the asterids among the eudicots, so the plants have trisulcate pollen, flower parts in fours and fives, fused petals with stamens adnate to a connate corolla. The stamens are normally equal to or less than the petal number.

Charyophyllales Characters: These plants have basal placentation and a uniseriate perianth.

Herbaceous shoots have swollen nodes, woody species have anomalous secondary growth with concentric rings of vascular bundles or alternative rings of xylem and phloem, of which have P-type sieve-tube plastids. Seeds have a perisperm and a little endosperm, which is curved around the perisperm. Plants contain betalains, a compound characteristic of this order.

Nyctaginaceae Characters: Plants are often weakly thorny with leaves that are simple and entire. The flowers are in bracteate groups of one or more. The perianth is a single connate whorl of tepals that are plicate and hug the ovary, which is actually superior though it looks inferior. The lobes are often valvate or contorted and the flowers are often bisexual. The gynoecium is a single simple pistil with a basal volume and the fruit is a drupe that is covered with a sticky secretion or clinging hairs.

Key Spot Characters: This family is easily recognized by their swollen nodes, opposite leaves, and oxidizing wood that quickly turns an orange or red-brown when cut. The perianth is tubular and resembles a corolla. The fruit is often covered by glands that produce a sticky secretion.

Ecology: Most species from this family are annual herbs and shrubs or small trees and lianas in forests. They are disturbance-colonizers and cultivated varieties are popular street trees.

Geography: found broadly across tropical and warm regions throughout the globe, though this family practically likes the New World. In Vermont, all the plants are from the genus Mirabilis and are herbs with swollen joints, opposite leaves, panicle flowers in five-parts with achene fruits enclosed in the calyx tube.

Image below is from GBIF showing the distribution of Nyctaginaceae.

Pollination and Dispersal: Many of these plants flower in the evening or night, giving them the name the “four o’clock family”. Moths appear to be the main pollinators of this family (Levin, Raguso, McDade 2000). This could be due in part to the later flowering of the plants, which make the flowers more available to nocturnal pollinators like moths. Other pollinators include bees, hummingbirds, and long-tongued flies. Inflorescences vary, and sometimes the green bracts look like a calyx and the brightly colored perianth looks like the corolla. The hypanthium on some species becomes viscous which aids in seed dispersal. The seeds are mostly likely bird-dispersed or via other animals due to their viscid exterior that allows them to stick on passerby’s.

Plant-Animal-Fungal Interactions: Caterpillars and Heliodinidae moths commonly mine leaves of this family. In the genus Anulocaulis the rings of sticky epidermal cells can help limit activities of herbivores like reducing ant-aphid associations (Angiosperm Phylogeny Website: Nyctaginaceae). The subfamily Pisonieae forms ectomycorrhizal associations with several basidiomycetes including Thelephoraceae.

Phytochemistry: Some medicinal uses of plants in this family include Bougainvillea treatments for coughing, asthma, and other respiratory conditions (Abarca-Vargas and Petricevich 2018). Compounds found in this genus include aliphatic hydrocarbons, fatty acids and fatty alcohols, volatile compounds, phenolic compounds, peltogynoids and flavonoids, phytosterols, terpenes, carbohydrates, and betalains (2018). Betalains are nitrogenous rings which are characteristic of Caryophyllales. Another study found that leaf proteins from Bougainvillea were able to degrade viral RNA viruses, which could be promising as a control for other vegetable viruses (Bhatia and Lodha 2005).

Ethnobotany: Besides the medicinal uses of the plants noted above, there are a few species that have the potential for food crops. The genus Mirabilis, specifically M. jalapa, has edible seeds with high protein content full of amino acids. A study by Ghosh, Nanak, and Bangeri investigating the chemistry of these plants found that M. jalapa not only is high in protein but also has anti- fungal, microbial, viral, spasmodic, and bacterial qualities (2013). This plant in particular is abundant in India, which makes this plant a promising protein alternative for the many humans who are undernourished in the area. Other uses include fodder, dye, lumber, and adhesives (Zant 2016). The main uses of these plants seem to be medicinal with a few side uses like those described above as well as aesthetic cultivation in gardens and cities.

Fun Paper & Key Takeaways: Fragrance chemistry and pollinator affinities in Nyctaginaceae (Levin, Raguso, and McDade 2000).

This paper looked at 20 species within three genera of the Nyctaginaceae, including Aclesianthes, Mirabilis, and Selinocarpus. The species found within these families were mainly pollinated by moths. The compounds studied were both vegetable and floral fragrances, including aromatics, aliphatic compounds, lactones, nitrogen-bearing compounds, and mono/sesquiterpenoids. The researchers found that each species had a different “fragrance profile” with a unique blend of volatile compounds that were species-specific. They found the most common volatile compounds were “ 4,8-dimethyl-nona-1,3,7-triene (present in all species), and trans-β-ocimene, cis-3-hexenyl acetate, and methyl salicylate (found in 18 of 20 species). There was also a preponderance of cis-3-hexenyl esters across all three genera”. Two species in this study were known to be pollinated by other animals (hummingbirds and bees) and it was found that they produced less volatile compounds than the solely moth pollinated species. The moth pollinated species had flowers wit ha “white-floral” order, where there was a variety of a cyclic terpene alcohols, simple aromatics, esters, jasmonates, tailgates, lactones, and nitrogen bearing compounds. These fragrances aiding in attracting pollinators from a distance. Since moths have poor vision and are mainly nocturnal, the combination of fragrance and later-blooming of the Nyctaginaceae flowers shows that these plants have a preference for moth pollinators.

Featured Faces:

Bougainvillea glabra is a common street tree, the brightly colored magenta bracts look like petals.The later two images are other varieties of Bougainvillea. All images below were of plants found on the Oaxaca field trip this spring (March 2020).

Works Cited

Abarca-Vargas, Rodolfo and Vera Petricevich. “Bougainvillea Genus: A Review on

Phytochemistry, Pharmacology, and Toxicology.” Evidence-Based Complementary and Alternative Medicine. 2018.

Bhatia, S. And M. Lodha “RNase and DNase additives of anti rival proteins from leaves of

Bougainvillea x. buttiana”. Indian Journal of Biochemistry and Biophysics. Vol. 42, Iss. 3. 2005

Douglas, Norman and Paul Manos. “Molecular Phylogeny of Nyctaginaceae: Taxonomy,

Biogeography, and Characters Associated with a Radiation of Xerophytic Genera in North America”. American Journal of Botany. Vol. 94 Iss. 5, 2007

GBIF (Global Biodiversity Information Facility) Updated 2020. https://www.gbif.org/species/6718

Ghosh, Asima; Anupam Nanak, and Julie Banergi. “Chemical Characterization of Seed Proteins of

Mirabilis jalapa (Nyctaginaceae)”. International Journal of Food Properties Vol. 17,

Issue. 3. 2013.

Levin, Rachel, Robert Raguso, Lucinda McDade. “Fragrance chemistry and pollinator affinities in

Nyctaginaceae”. Phytochemistry Vol. 58, Issue 3, 5 December 2000.

Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 14, July 2017

http://www.mobot.org/MOBOT/research/APweb/

Zant, Miriam Kritzer Van. “Review of the Economic and Ethnobotany of the Family

Nyctaginaceae” Atlas Journal of Biology 2016