Black mangrove (Avicennia

germinans)

The black mangrove (Figure 17) tends to be located behind the red mangrove, in sal er and less aerated soils. This species tolerates more strenuous climate condi ons and is associated with poor soils or soils with high salinity.

Main characteris cs:

Leaves: The black mangrove’s leaves are smaller than the red mangrove’s, and are lanceolate, with a sharp point at the apex (Figure 18). The dorsal surface (the top side of the leaf) is green, while the ventral surface (the bo om side of the leaf) is yellowish green and opaque (Figure 19). Black mangrove leaves are opposite (begin at the same point on the branch, but in opposite direc ons) and serve as the tree’s salt excretory organs (Figure 18). The salt crystals are deposited on the dorsal surface through stoma. This process ensures that the tree maintains the necessary water it needs for its survival. Older leaves tend to accumulate higher concentra ons of salt before falling off and showing burn spots due to the “magnifying glass” effect created when sunlight is filtered through the salt crystals.

Roots: The black mangrove features a system of super cial roots around the trunk. This system has several long projec ons which protrude from the substrate upwards. These projec ons are known as pneumatophores (Figure 20). The pneumatophores are long and slender (reaching a height of up to 20 cm), and their func on is to allow the mangrove to perform aera on (breathing) in poorly oxygenated soils. Because of their appearance and func on, they are o en referred to as “snorkel roots.”

Bark: The black mangrove tree’s bark has a smooth bark while in the juvenile stage, before becoming fissured. It has a black or dark gray color, with a yellowish interior (Figure 23).

Flowers: Black mangrove flowers are small (0.2 - 0.5 cm in diameter, 0.5 cm in height), with white petals. They bloom in dense clusters (Figure 21).

Fruit: The black mangrove’s fruit is shaped like a small, fla ened, oval capsule (Figure 22). The embryo develops while s ll a ached to the parent tree, and fixes itself onto the substrate upon falling. If it falls into the water, the embryo can float for several weeks, sustaining itself on the cotyledons, un l it reaches an appropriate place on which to se le.

Apex - the outer end of a leaf or branch.

Cotyledons - the shape in which the first leaf of a seed-bearing plant embryo appears.

Dorsal surface - the top side of a plant’s leaf.

Stoma - small pore-like orifices located on a leaf’s surface; they are in charge of regula ng gas Exchange and minimizing water loss.

Ventral surface - bo om or inferior surface on a plant’s leaf.