Wheat leaf. Light micrograph (LM) of a transverse section through the leaf (pinna) of a wheat. Wheat is one of the world's most commonly consumed cereal grains. It comes from a type of grass (Triticum) that is grown in countless varieties worldwide. The spongy mesophyll has air spaces for gas exchange and produces carbohydrates by photosynthesis. 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. In monocot leaf, both small and large parallel vascular bundles are present. Magnification: x20 at 10 centimetres wide.