Lamiales

Order of Lamiids (Euasterids I)

Food, Plant source foods, Flowering plats (angiospermae), Mesangiosperms, Eudicots, Core eudicots, Superastierds, Asterids, Lamiids (Euasterids I)

Consumption area(s): Earth

Note: For better understanding, please read the article on flowering plants (angiospermae) first. If you come across unfamiliar words, you can click on any highlighted term to open the glossary with definitions of key botanical terms.

Introduction

The Lamiales, commonly referred to as the mint order, form a large group of flowering plants placed within the asterid lineage of the Eudicots. This order is composed of 24 distinct families, encompassing roughly 1,059 genera and an estimated 23,810 recognized species. Members of the Lamiales have a global distribution, with representatives occurring in many regions of the world, reflecting their wide ecological adaptability.

Description of Lamiales

The growth forms in this order are highly diverse. Plants may be herbaceous, either annual or perennial, while others take the shape of shrubs or tall trees exceeding twenty meters. There are also evergreen species, climbers, suffruticose plants, or with tuberous roots. In some cases, aquatic or semi-submerged habits occur. Certain groups include perennial plants acting as parasites, with underground buds and roots specialized to draw sap from hosts. Others lack chlorophyll and turn brown when dry, due to orobanchin.

The stems often appear square in cross-section, caused by collenchyma bundles at the corners. The outer layer may show simple hairs, but also branched, dendritic, or stellate trichomes. Vegetative tissues store compounds like phenolic glycosides, iridoids, alkaloids, diterpenoids, and sugars such as stachyose. Essential oil glands are frequent, producing distinctive fragrances.

The leaves are usually opposite, but can also be alternate or spiral. In some species they form whorls, with two, four, or up to seven leaves per node. The lamina may be sessile, petiolate, or clasping, and shapes range from lanceolate to ovate, with edges that can be entire, lobed, dentate, crenate, or wavy. Pinnate leaves and basal rosettes also occur.

Some species display anisophylly, and others have salt glands that excrete saline solutions, which crystallize into salt deposits. Leaf venation is most often pinnate, and in many taxa the leaves are showy and patterned.

The inflorescences may be cymose (determinate) or racemose (indeterminate). In the Lamiaceae, flowers grow in axillary whorls, with two to twenty flowers arranged around leaflike bracts. Other groups form spikes, cylindrical or tetragonal, often with large, colorful bracts that expand and overlap. At times, one or two bracteoles appear beneath the calyx, adding further variation to the floral structures.

The flowers in this order are mostly hermaphroditic and usually tetramerous, with four whorls: calyx, corolla, androecium, and gynoecium. They are often pentamerous, with five elements in each whorl, though in some cases only four appear.

The calyx is generally gamosepalous and nearly actinomorphic, though it may show weak zygomorphy. It usually consists of 3 to 5 lobes, sometimes up to 8 in certain Oleaceae. The calyx tube is tubular or bell-shaped, and in some species it is accompanied by bracteoles that thicken at maturity.

The corolla is gamopetalous, most often zygomorphic, and shaped like a tube that ends in two lips with five lobes. Surface texture ranges from hairy to glabrous, and a ring of hairs at may block unsuitable pollinators. Corolla coloration is highly diverse.

The androecium usually has 2 to 5 stamens, most often four didynamous, though some groups have up to 8. The filaments are adnate to the corolla but free at the top, sometimes hairy. Anthers are paired, with two thecae, opening mainly longitudinally. Pollen varies from tricolpate to hexacolpate. A conspicuous nectary disc is usually present, producing abundant nectar for pollinators.

The gynoecium most often has two carpels, and more rarely three and typically has a superior ovary. False partitions often create two to four chambers, with axile placentation. Each ovary can bear from 2 to more than 100 ovules, which are tenuinucellate with a reduced nucellus. The style is filiform, often gynobasic, and the stigma is usually bifid, with equal or slightly unequal lobes.

The fruits show remarkable variation, including capsules, drupes, and schizocarps. Shapes range from rounded to ellipsoid, with surfaces that may be smooth or hairy. Dehiscence occurs in different ways: loculicidal, septicidal, circumscissile, or irregular. In Pedaliaceae, fruits are woody and indehiscent, while Martyniaceae produce capsules with long hooked projections.

The seeds are often numerous and fragile, sometimes reaching thousands per fruit. They are usually ellipsoid, brown to yellow, smooth-coated, and may lack endosperm.

Pollination in this order is primarily insect-pollinated, carried out by insects such as bees, wasps, butterflies, moths, flies, and beetles, as well as by birds in some cases. In certain species, the corolla lobes can rotate, bringing the stamens into contact with visiting pollinators. Some plants have cleistogamous flowers, which remain closed and self-pollinate.

Classification of Lamiales

This order is further divided into several families. Among the most notable are:

• Acanthaceae (barleria)
• Bignoniaceae (catalpa)
• Gesneriaceae (African violet)
• Lamiaceae (basil, mint, oregano, rosemary, sage, thyme)
• Martyniaceae (martynia)
• Oleaceae (olive)
• Pedaliaceae (sesame)
• Plantaginaceae (psyllium)
• Scrophulariaceae (scrophularia)
• Verbenaceae (verbena)