These nematodes, sold under the names of Scanmask and Nemasys, are microscopic, wormlike creatures that will destroy the fungus gnats but are not harmful to people, pets, plants, or earthworms. These products can be used whenever the soil is not frozen and will keep working for many months.
Vegetative structures. There are three levels of integrated organization in the vegetative plant body: organ, tissue system, and tissue. The organs of the plantâthe roots, stems, and leavesâare composed of tissue systems (dermal tissue, ground tissue, and vascular tissue; see below Tissue systems).
1 Tissues â Groups of cells that are similar in appearance and function, for example: 2  Epidermis is the single exterior layer that protects the stems, leaves, flowers, and roots.3  The outside surface of the epidermis tissue is usually covered with a waxy substance called cutin, which reduces water loss.n reviewing plant physiology, plant cells are grouped into tissues based on similar characteristics, then into five distinct structures (organs).