Agriculture Reference
In-Depth Information
Adaxial epidermis
Palisade cells
Spongy mesophyII
Stoma
Hair
Abaxial epidermis
Figure 7.1
Apple leaf in 3-dimensional diagram showing epidermis,
palisade cells,spongy mesophyll,minor veins,stomata and a hair.
From MacDaniels and Cowart (1944). Originally drawn by
Rita B. Eames.
stomatalporelengthof
-
µ
mwiththedistancebetweentheporecentresof
m depending on cultivar.
Theappleepidermishasunicellularhairs,originatingfromsingleepidermal
cells. They are abundant on both surfaces of young leaves but occur primarily
on the abaxial surface of lower leaves. These may have an adaptive function in
reducingwaterlossbymaintaininghumidairneartheleafsurface.Theepider-
mis also has simple hydathodes associated with vascular tissue on the adaxial
surface, at the margins and tips of leaves and at the end of minor veinlets. There
are also glandular hairs with stalks and multicellular heads which contain
secretory cells. The secretions may favour the growth of parasitic organisms.
This basic leaf structure varies with a number of factors. At least some spur-
type cultivars have thicker leaves and a greater number of palisade layers than
the corresponding standard cultivars (Liu and Eaton,
-
µ
). The number of
palisade mesophyll cells per unit area of leaf lamina, which depends on cell
diameter, the number of palisade layers and the amount of intercellular space,
is greater in vigorous than in dwarf apple rootstock cultivars (Beakbane,
),
