botany unit 2 vocab

cell theory

three general conclusions about structure and function of living organisms, developed in the mid nineteenth century: all organisms are made up of one or more cells, the cell is the basic unit of structure and all cells come from existing cells

selectively permeable

describes a membrane that transports some molecules but not others across the cell membrane

fluid mosaic model

the structure of the plasma membrane consists of a layer of phospholipid molecules; these long molecules have a water soluble and water insoluble end; the water soluble end faces the external and internal surfaces of the membrane. Proteins are associated with either side of the membrane or may pass directly through it. 

diffusion

 tendency for molecules to spread out spontaneously within the available space, from a region of higher concentration to lower concentration 

active transport

an energy requiring process, generally using ATP, in which small molecules are transported across a membrane up a concentration gradient; uses one or more transport proteins

meristematic

relating to the region of plant tissue consisting of actively dividing cells forming new tissues

apical meristems

 a region of actively dividing, undifferentiated plant cells located at the tip of the roots and shoots; responsible for primary growth

parenchyma

a soft cellular tissue found in the softer parts of leaves, pulp of fruits, and the pith of stems

collenchyma

a supporting tissue that provides support, structure, and mechanical strength to plants; helps them stand up to strong winds 

sclerenchyma

a plant tissue composed of dead cells with lignified cell walls, providing mechanical strength and support 

dermal

the outermost protective layer of the plant that covers the roots, stems, leaves, and flowers. This protects the plant from external threats

xylem

the vascular tissue in plants that conducts water and dissolved nutrients upward from the root and also helps to form the woody element in the stem

tracheids

a type of water conducting cell in the xylem which lacks perforations in the cell wall

vessel elements

specialized, water-conducting cells found in the xylem tissue of plants, particularly angiosperms

phloem

the vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves

sieve tube members

specialized, elongated cells in the phloem of flowering plants that form sieve tubes (primary conducting cells of the phloem) to transport sugars

companion cells

specialized parenchyma cells in the phloem of vascular plants that support sieve tube elements by regulating nutrient transport

cortex

an outer layer of tissue immediately below the epidermis of a stem or root.

pith

the soft, spongy, central cylinder of tissue found inside the stems of plants and serves as a storage area

transpiration

 water evaporation from plants through the stoma