Syringa Leaf (dicot)




Syringa (lilac, a dicot) leaf cross section, 100X.
A = palisade mesophyll; B = upper cuticle; C = xylem; D = phloem; E = upper epidermis; F = vein (vascular bundle); G = lower epidermis; H = lower cuticle; I = spongy mesophyll; J = guard cell; K = stoma

Function:
The palisade mesophyll produces carbohydrates by photosynthesis. The spongy mesophyll below has numerous air spaces to allow gas exchange between the mesophyll and the outside air via the stomata. The upper and lower cuticle protect the leaf from water, sealing water inside and preventing excess rainwater from entering. The upper and lower epidermis produce the cuticle and protect the leaf from herbivores and parasites. The xylem transports water into the leaf while the phloem begins the sugar transport down to the roots. The guard cells open and close the stoma, which is the small air space between them.

Tissue Breakdown:
Epidermal tissue: epidermis.
Ground tissue: palisade and spongy mesophyll.
Vascular tissue: xylem and phloem in vein.
Meristem tissue: none (leaves cannot grow new leaves).

At 40X, micrograph width = 2 mm; at 100X, micrograph width = 0.8 mm; at 400X, micrograph width = 0.2 mm; at 1000X, micrograph width = 0.08 mm.