Although apple (Malus spp.) and pine (Pinus spp.) Seedlings share the identical basic functional components, their structure and arrangement are different, as are the methods that the seeds are produced. The components that the seedlings have in common are a seed coat, a seed root referred to as a radicle, and a stem called a hypocotyl. Their seed leaves vary markedly in form and number. These differences reflect the reality that pines and apples aren’t closely related. All these are seed plants, but pine is a gymnosperm and apple is a flowering plant with two seed leaves, or a dicotyledonous angiosperm.
The fundamental differences between pine and apple seedlings begin with the seeds that make the seedlings. Pine seeds develop in a bract of the female pine cone, and aren’t surrounded by a fruit. Apple seeds develop within the ovary of the apple flower, enclosed with a hexagonal wall that grows into a fruit. Many pines have small winged seeds designed for wind dispersal, but about 30 of the 110 species have heavy seeds built for animals to propagate. In apples, the fruit becomes eaten and the small, hard seeds pass unharmed through an animal’s digestive tract.
Within the Seed
Both pine and apple seeds have a plant embryo that develops to the seedling. Pines have an elongate embryo in the middle of the seed surrounded by a thick layer of nutritive substance. Apple seeds are largely taken up with 2 big seed leaves and also a thin layer of nutritive endosperm, which differs in origin from the nutritive layer of pine tree seeds. The embryonic tissues that become the the radicle take up relatively little room toward the base of the seed.
Germination in both pines and apples starts with the emergence of the radicle, which anchors the developing seedling and harvests nutrients and water so it can grow. In pine seedlings, the radicle splits the seed coat since it emerges, with the mineral substance surrounding the embryo supplying the energy for development. In apple seeds, then the stored nutrients in the cotyledons fuel seedling growth until plants begin to make their own food through photosynthesis. Apples and pines both require a period of moist cold in order to germinate, and also both apples and pines are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 8.
The amount of seed leaves in pine seedlings varies from 2 to many, depending on the species. Ponderosa pine (Pinus ponderosa), which grows in USDA zones 4 through 8, has anywhere from six to 12 cotyledons. The cotyledons are very long, narrow and stiff, reflecting the needle-like form of their true leaves to follow. They’re arranged in a whorl around the stem of the seedling. Apple’s seed leaves are oval and fleshy-looking, arranged opposite each other at the tip of the seedling stem.
True leaves emerge as the seedlings grow. In pine seedlings, needle-like true leaves appear together with the growing shoot above the cotyledons. As the tree grows, it starts to create the leaves in bundles, called fascicles, which can consist of from one to eight needles, depending on the species. In apples, elongated oval true leaves with jagged edges emerge as the apical shoot grows from between the two cotyledons.