Cambium: A layer of living cells between the bark and hardwood that each year produces additional wood and bark cells, forming concentric growth rings.Xylem: Plant tissue that carries water up the root and stem. Xylem cell walls derive most of their strength from LIGNIN. The vessels are similar to PHLOEM sieve tubes but lack companion cells and do not have perforated sides and pores.Plant Stems: Parts of plants that usually grow vertically upwards towards the light and support the leaves, buds, and reproductive structures. (From Concise Dictionary of Biology, 1990)Phloem: Plant tissue that carries nutrients, especially sucrose, by turgor pressure. Movement is bidirectional, in contrast to XYLEM where it is only upward. Phloem originates and grows outwards from meristematic cells (MERISTEM) in the vascular cambium. P-proteins, a type of LECTINS, are characteristically found in phloem.Populus: A plant genus of the family SALICACEAE. Balm of Gilead is a common name used for P. candicans, or P. gileadensis, or P. jackii, and sometimes also used for ABIES BALSAMEA or for COMMIPHORA.Plant Vascular Bundle: A strand of primary conductive plant tissue consisting essentially of XYLEM, PHLOEM, and CAMBIUM.Abies: A plant genus in the family PINACEAE, order Pinales, class Pinopsida, division Coniferophyta. Balm of Gilead is a common name more often referring to POPULUS and sometimes to COMMIPHORA.Wood: A product of hard secondary xylem composed of CELLULOSE, hemicellulose, and LIGNANS, that is under the bark of trees and shrubs. It is used in construction and as a source of CHARCOAL and many other products.Eucommiaceae: A plant family of the order Eucommiales, subclass Hamamelidae, class Magnoliopsida (some botanists have classified this in the order Hamamelidales or Urticales). Eucomia is an elmlike tree of central and eastern China. Leaves are alternate; deciduous flowers are solitary and unisexual and lack petals and sepals. The male flowers have 6 to 10 stamens and female flowers have one ovary of two carpels, one of which aborts during development so the fruit (a dry, winged structure) contains only one seed. The latex is a source of RUBBER. Tochu tea is an aqueous extract of Eucommia ulmoides leaves and a popular beverage in Japan. (Mutat Res 1997 Jan 15;388(1):7-20).Periosteum: Thin outer membrane that surrounds a bone. It contains CONNECTIVE TISSUE, CAPILLARIES, nerves, and a number of cell types.Cryptomeria: A plant genus of the family TAXODIACEAE. Its POLLEN is one of the major ALLERGENS.Inflorescence: A cluster of FLOWERS (as opposed to a solitary flower) arranged on a main stem of a plant.Meristem: A group of plant cells that are capable of dividing infinitely and whose main function is the production of new growth at the growing tip of a root or stem. (From Concise Dictionary of Biology, 1990)Ipomoea batatas: A plant species of the genus IPOMOEA, family CONVOLVULACEAE. Some cultivars are sweet and edible whereas bitter varieties are a source of SAPONINS. This sweet potato is sometimes referred to as a yam (DIOSCOREA).Picea: A plant genus in the family PINACEAE, order Pinales, class Pinopsida, division Coniferophyta. They are evergreen, pyramidal trees with whorled branches and thin, scaly bark. Each of the linear, spirally arranged leaves is jointed near the stem on a separate woody base.Araliaceae: The ginseng plant family of the order Apiales, subclass Rosidae, class Magnoliopsida. Leaves are generally alternate, large, and compound. Flowers are five-parted and arranged in compound flat-topped umbels. The fruit is a berry or (rarely) a drupe (a one-seeded fruit). It is well known for plant preparations used as adaptogens (immune support and anti-fatigue).Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.Indoleacetic Acids: Acetic acid derivatives of the heterocyclic compound indole. (Merck Index, 11th ed)Gene Expression Regulation, Plant: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in plants.Plant Growth Regulators: Any of the hormones produced naturally in plants and active in controlling growth and other functions. There are three primary classes: auxins, cytokinins, and gibberellins.