ABCs of Plant Parts

Aril: "special covering of certain seeds that commonly develops from the seed stalk, often a bright-coloured fleshy envelope, as in such woody plants as the yews and nutmeg and in members of the arrowroot family."

http://www.britannica.com/EBchecked/topic/34297/aril

Blade of a leaf is the expanded, thin structure on either side of the midrib most conspicuous part of a leaf 

Calyx: the outermost whorl of parts that form a flower

Dentate:

Having teeth ending in an acute angle, pointing outward.

Epidermis a layer of thickened, tough cells, the primary function being protection of leaf tissue
Fibrous root system primary root ceases to elongate, leading to the development of numerous lateral roots
Guard cells regulate the passage of water, oxygen, and carbon dioxide through the leaf.

Heartwood : The innermost, hardest wood of a tree. Compare to sapwood.

Inflorescence : a term which refers to a cluster of flowers and how they are arranged on a floral stem

Juvenile leaf : Term applied to first few leaves with green, expanded lamina developed by seedlings

karyogamy: fusion of nuclei

Midrib:  The vein running down the middle of a leaf from the petiole or leaf base to the leaf tip

Nodes areas of great cell activity and growth

Ovule: The haploid female reproductive cell, located in the Ovary
Peduncle: The stem or stalk of a scape, topped by the inflorescence.

Quizlet: Plant Biology Terms

Receptacle: see above

Sepal: a part of the flower of angiosperms(flowering plants). Collectively the sepals are called the calyx 
Terminal bud: the bud located at the end of a twig marking the end of that year's growth
Umbel: Inflorescence in which several nearly equal flower stalks radiate from top of the peduncle The result is a hemispherical to spherical flower head.
Venation refers to the patterns in which the veins are distributed in the blade.

Whorl is an arrangement that radiate from a single point and surround or wrap around the stem

Xylem vessels conduct water and minerals, while phloem tubes conduct food
Yellow carotenoid pigments found in the chromoplasts of leaves and petals are called Xanthophyll
Zone of elongation in which cells increase in size through food and water absorption

sources: http://ag.arizona.edu/pubs/garden/mg/botany/plantparts.html

http://ag.arizona.edu/pubs/garden/mg/botany/leaves.html#leaves

http://quizlet.com/333332/plant-biology-terms-flash-cards/

http://www.shieldsgardens.com/info/Glossary.html