Seedling

The plumule is the part of a seed embryo that develops into the shoot bearing the first true leaves of a plant.

Dicot seedlings grown in the light develop short hypocotyls and open cotyledons exposing the epicotyl.

In contrast, seedlings grown in the dark develop long hypocotyls and their cotyledons remain closed around the epicotyl in an apical hook.

Etiolated seedlings are yellowish in color as chlorophyll synthesis and chloroplast development depend on light.

The opening of the cotyledons exposes the shoot apical meristem and the plumule consisting of the first true leaves of the young plant.

Seedling growth is also affected by mechanical stimulation, such as by wind or other forms of physical contact, through a process called thigmomorphogenesis.

[3][4] The effects of carbon dioxide enrichment and nitrogen supply on the growth of white spruce and trembling aspen were investigated by Brown and Higginbotham (1986).

[5] Seedlings were grown in controlled environments with ambient or enriched atmospheric CO2 (350 or 750 f1/L, respectively) and with nutrient solutions with high, medium, and low N content (15.5, 1.55, and 0.16 mM).

In white spruce only, the root weight ratio (RWR) was significantly increased with the low-nitrogen regime.

First-year seedlings typically have high mortality rates, drought being the principal cause, with roots having been unable to develop enough to maintain contact with soil sufficiently moist to prevent the development of lethal seedling water stress.

He commented that in dry habitats after the first growing season surviving seedlings appeared to have a much better chance of continued survival than those in moist or wet habitats, in which frost heave and competition from lesser vegetation became major factors in later years.