Plants grow in two ways, taller and thicker. Conifers and three quarters of flowering plants grow thicker by means of the cambium or growth tissue found in the phloem and xylem. In trees the xylem hardens to form wood. Each year a layer of wood grows outside the previous layer and the tree grows thicker. The growth rings tell the age of the tree. Plants get taller thanks to growth tissue at the ends of branches and roots. These growth tissues are protected in buds during the winter but open and leaves furl in the spring as the stem grows longer. In temperate regions plants grow only in Spring and Summer. In the intertropical zone, plants grow continuously.

Originally released by QA International, 2006. Streaming video file encoded with permission for digital streaming by Infobase on May 06, 2015.

Plant Growth (French) (1:00); .