Rosaceae

The Rosaceae family includes 4828 known species of flowering plants in 91 genera. They are primarily concentrated in the Northern Hemisphere, in regions that are not desert or tropical rainforest.

Systemic classification

Kingdom: Plantae

Division: Angiosperm

Class: Dicotyledones or magnoliopsida

Sub-class: Rosidae 

Order: Rosales

Habitat

These are annual, perennial or everlasting plants that are primarily trees or shrubs. They are rarely herbaceous.

Root

These plants have a taproot system. Adventitious roots arise upon stem cutting.

Stem

Plants of the Rosaceae family have erect, branched, hard and woody prostrate or climber stems. Vegetative propagation occurs by means of runners, suckers and cutting. Shrubby species bear spine-like outgrowths. These outgrowths are cortical and arise from both nodes and internodes.

Leaves

These plants have simple or pinnately compound leaves. Most of them have alternate phyllotaxy (leaves arranged on the stem). However, opposite phyllotaxy is observed in Rhodotypos.

Plants of the Rosaceae family are stipulate, i.e., they have leaf-like appendages on the base of the petiole. Stipules are represented by epicalyx in Fragaria and Potentilla. Spines are present on the midrib of leaflets and the rachis of compound leaves.

Flower

The flowers of these plants are mostly actinomorphic. Zygomorphic or bilaterally symmetrical flowers are found in Chrysobalanoidae. They are also bisexual (or hermaphrodite), i.e., both the stamen and the carpel are found in the same flower. 

These flowers can be pentamerous or tetramerous. They have numerous free stamens that are spirally arranged.

In these flowers, the bases of petals, sepals and stamens are fused to form a cup-like structure called hypanthium. It is lined by nectar-producing tissues. Solitary flowers are rare.

Seeds

The seeds are non-endospermic or exalbuminous. They have two cotyledons, along with one embryonal axis.

Fruits

Fruits can be follicles, capsules, nuts, achenes, drupes (prune), and accessories, such as the pome of an apple and the hip of a rose.

Many fruits of the family are edible. But their seeds often contain amygdalin, which can release cyanide during digestion if the seed is damaged.

Calyx

The calyx has five sepals. The flowers are polysepalous (sepals are free). The calyx tube remains free or adnate to the ovary.

Corolla

The corolla consists of five or more petals. The flowers are polypetalous, rosaceous, and inserted in the receptacle cup. Petals are absent in Proterium, Alchemilla, Pygeum gardneria. However, the Rosa subspecies has indefinite petals that are variously coloured (except blue).

Androecium

The flowers have indefinite and free stamens borne on the rim of the torus. Anthers are small, dithecous and introrse in buds. Dehiscence of anthers occurs by longitudinal splitting.

Gynoecium

The gynoecium has one carpel in Prunus and Prinsepia and five carpels in Pyrus. It has indefinite carpels in Rosa and Fragaria. If the carpels are apocarpous, gynoecium shows basal placentation, and if they are syncarpous, the gynoecium shows axile placentation. The carpels have two to five locules.

Pollination

The transfer of pollen grains mainly occurs by insects, i.e., the flowers are entomophilous. But, in some cases, it also occurs by means of air currents or wind (anemophily).

Economic importance of Rosaceae family

• Apple, peach, loquat, pear, plum and mulberry are examples of some edible fruits that belong to the Rosaceae family.
• Petals of rose are used in making gulkand, rose water, and scent.
• The fruits of Prunus domestica are used to treat leucorrhoea and irregular menstruation.
• Fruits of Amygdalus persica and Persica vulgaris (peach) are edible and vitamin-rich. The oil obtained from the seeds of these plants is used for cooking and other purposes.
• Spiraea corymbosa is a small shrub that is grown in the garden as an ornamental plant.
• Rosa centifolia (Cabbage rose) is a herb or small shrub. The petals of this plant yield an essential oil that is used in making perfumes and cosmetics.
• Crataegus oxycantha is found in the Himalayas. Its wood is hard and hence is used in making tool handles.

Conclusion 

Rosaceae have non-herbaceous, woody stems and are mostly shrubs or medium-sized trees. Certain species have thorns and prickles, which act as a defence mechanism against the herbivores. Rosaceae have stipules that are leaf-like appendages present at the base of the petiole and exhibit alternate phyllotaxy. They have radially symmetrical and bisexual flowers. The gynoecium consists of five or more carpels with superior, inferior, half-superior, or half-inferior ovary. The androecium has indefinite and free stamens. The presence of hypanthium is unique to the members of the Rosaceae family.