A seedling is the young plant that develops from a plant embryo following the germination of a seed. This stage represents the beginning of the plant’s independent life, bridging the gap between the dormant seed and the established juvenile plant. The developmental process starts when the seed breaks dormancy and begins to grow under favorable conditions. This initial phase is a transformation from relying on stored energy to becoming a self-sustaining organism, characterized by rapid structural development and vulnerability to environmental conditions.
Identifying the Key Parts of a Seedling
A typical seedling is composed of three primary structures that are visible shortly after emergence. The first part to emerge from the seed is the radicle, which is the embryonic root that quickly anchors the young plant and begins absorbing water and nutrients from the soil. Above the radicle is the hypocotyl, which acts as the embryonic stem, connecting the root to the seed leaves. The epicotyl is the small portion of the stem situated above the seed leaves.
The most distinctive features of this stage are the cotyledons, often called seed leaves, which are the first structures to appear. These cotyledons differ significantly from the plant’s later foliage because their initial function is not primarily photosynthesis but rather to serve as a temporary food source. They contain the energy reserves that fuel the seedling’s growth until it can produce its own food. Once the plant develops its first true leaves, which resemble the mature plant’s foliage, the cotyledons usually shrivel and drop off as their function is complete.
The Process of Seedling Emergence
The transformation from seed to seedling begins with a process called imbibition, where the dormant seed rapidly absorbs water from the surrounding soil. This water intake causes the seed to swell, which activates enzymes and metabolic processes necessary for growth, eventually leading to the rupture of the seed coat. The radicle is always the first structure to emerge, pushing downward to establish a root system for stability and water uptake.
The physical act of the shoot breaking the soil surface follows one of two main patterns. In epigeal germination, common in beans and sunflowers, the hypocotyl elongates, forming a hook that pulls the cotyledons and the developing shoot tip up and out of the ground. Conversely, in hypogeal germination, seen in peas and corn, the epicotyl is the part that elongates, leaving the cotyledons safely below the soil surface while the shoot pushes upward.
Caring for Seedlings
Once the seedling has emerged, its survival depends on carefully managed environmental inputs. Light is a major requirement, with most vegetable seedlings needing between 14 to 16 hours of bright light daily to prevent them from stretching and becoming weak, a condition known as etiolation. If natural light is insufficient, supplemental grow lights must be placed close to the foliage to provide the necessary intensity.
Water management is equally important, as young plants are susceptible to fungal diseases like damping off if the soil remains waterlogged. Watering from the bottom is often recommended, allowing the soil to wick up moisture and encouraging deeper root growth while keeping the stem base dry.
Seedlings benefit from warm soil temperatures, often between 70 to 80 degrees Fahrenheit for warm-season plants, which can be maintained using a simple heat mat beneath the container. Fertilization should only begin once the true leaves have developed, using a diluted solution of a balanced fertilizer that provides nitrogen, phosphorus, and potassium.