Asterids

Clade of Superasterids

Food, Plant source foods, Flowering plats (angiospermae), Mesangiosperms, Eudicots, Core eudicots, Superastierds

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

In modern plant classification, the term asterids refers to a group of dicotyledonous seed plants that belong to the broader category of angiosperms. These plants share certain traits that suggest a common evolutionary history.

Among eudicot flowering plants, asterids represent one of the two main branches, alongside the Rosids. Together, these two groups form the central framework used to organize the majority of known eudicots, which include a vast range of familiar and diverse species.

Description of Asterids

The growth forms found within this clade are highly diverse, ranging from annual or perennial herbs to shrubs, and even trees that may exceed 20 meters in height. Occasionally, some species exhibit aquatic habits, and a few develop liana-like structures. Within Ericales, evergreen shrubs are prevalent.

Leaf arrangement is equally diverse. Leaves can be opposite, alternate, or spirally arranged, occasionally forming basal rosettes or whorl of two to seven. Stipules may be present or absent. Leaf blades vary: some are sessile, others petiolated or amplexicaul. Their shapes range from lanceolate to ovate, with borders that may be entire, lobed, crenate, toothed, or wavy. Pinnate leaves can also be found. In certain species, the venation pattern is palmate.

Their inflorescence structures span an evolutionary spectrum: both cymose (determinate) and racemose (indeterminate) arrangements appear. In some families, inflorescences are stacked axillary whorls, while others bear spikes. Flower heads, enclosed by rings of bracts, are frequent—especially in Asteraceae. In Apiales, flowers emerge from a central point, forming a classic umbel.

Flowers can be bisexual or unisexual, most frequently tetramerous, structured around four whorls: calyx, corolla, androecium, and gynoecium. Exceptions with five to eight parts do occur, particularly in Cornales. Stamens are often epipetalous and as numerous as or fewer than the corolla lobes, though in Ericales, their number may double, reaching ten. Flower symmetry can be actinomorphic, or zygomorphic. Some families exhibit resupination, a floral twist during development.

The calyx typically consists of fused sepals (gamosepalous) and is often actinomorphic, but may show zygomorphic. In some families, the calyx is replaced or supplemented by a pappus, aiding seed dispersal. The corolla, generally gamopetalous, often displays a zygomorphic but occasionally the petals are free. In Ericales, urceolate corollas are frequent.

The androecium aligns with the calyx and corolla in structure and number. Filaments are often attached to the corolla, but usually become free toward their upper portion. Anthers tend to be tetrasporangiate, basifixed, and introrse, with bilocular structure. Most pollen is tricolpate, though other forms with varied apertures exist.

The gynoecium generally comprises a superior ovary that often includes two (sometimes three) fused carpels, withdifferent types of placentation.. The style is typically gynobasic and filiform, and the stigma usually splits into two lobes, equal or uneven.

Fruit types vary widely: capsules, drupess, and schizocarps. Shapes range from bilobed to oblong or ellipsoid. Fruit opening mechanism can be explosive, septicidal, sometimes also circumscissile, or through a more or less irregular dehiscence. Alternatively, the fruits may be woody or leathery and indehiscent.

From an ecological standpoint, insect pollination predominates, involving bees, flies, beetles and birds. Some species self-fertilize without opening their flowers (cleistogamy), which self-pollinate without opening. Colorful bracts and vivid petals enhance pollinator attraction.

Reproductive success hinges on pollination, followed by various seed dispersal strategies: some seeds are carried by wind, others by ants drawn to nutrient-rich fat bodies on the seed surface. Birds and mammals help disperse fleshy fruits, and in some cases, seeds float on water currents to new habitats.

Classification of Asterids

This clade is further subdivided into clades:

• Campanulids (carrots, celery, elderberry, lettuce, parsley, parsnip), which would form the clade Euasterids together with the Lamiids, but which have been omitted here.
• Cornales (dogwoods)
• Ericales (blueberries, kiwifruit, persimmons)
• Lamiids (basil, bell peppers, chili peppers, coffee, eggplants, mint, olives, oregano, periwinkle, potatoes, rosemary, sage, sesame, thyme, tomatoes), which would form the clade Euasterids together with the Campanulids, but which have been omitted here.