xylem cell造句

• Xylem cells are elongated cells with lignified secondary thickening of the cell walls.
• Wood is primarily composed of xylem cells with cell walls made of cellulose and lignin.
• Some xylem cells carry water and nutrients up from the roots, while others store food.
• Streptococcal bacteria have been found living inside the walls of water-conducting xylem cells in spent reeds.
• The movement in phloem is multidirectional, whereas, in xylem cells, it is unidirectional ( upward ).
• Since xylem cells comprise dead, lignified tissue, subsequent rings of xylem are added to those already present, forming wood.
• Vessel members are hollow xylem cells without end walls that are aligned end-to-end so as to form long continuous tubes.
• The cambium cells toward the inside of the tree become xylem cells, part of the sapwood, or living wood, of the tree.
• Additional layers may be formed by lignin in xylem cell walls, or suberin in leaf stalk may acquire similar reinforcement to resist the strain of physical forces.
• The bryophytes lack true xylem cells, but their sporophytes have a water-conducting tissue known as the hydrome that is composed of elongated cells of simpler construction.
• The wood of " Ruptiliocarpon " was different from the wood of all others to which it was compared in having vestured pits on the walls of its xylem cells.
• Secondary growth consists of a progressive thickening and strengthening of the tissues as the outer layer of the epidermis is converted into bark and the cambium layer creates new phloem and xylem cells.
• Xylem cells are specialised for conduction of water, and first appeared in plants during their transition to land in the Silurian period more than 425 million years ago ( see " xylem vessels.
• The vascular cambium forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, and those on the outside forming secondary phloem cells.
• The accumulation of hexose sugars ( glucose, fructose ) is associated with the development of xylem cell discontinuities which reduce the volume of water entering the berry relative to the volume of sugar, resulting in an increase in sugar concentration.