Populus tremuloides (quaking aspen) Laterally compressed petioles allow any breeze to cause leaves to vibrate or "quake". This movement makes it difficult for insects to land on or crawl on leaf surfaces.
Populus grandidentata (big tooth aspen) Trichomes may form a dense mat that is a physical barrier to insects
Populus alba with trichomes that remain on leaf.
Populus grandidentata (young leaf) Dense mat of trichomes that abscise when leaf is fully expanded
Populus grandidentata Young leaf with trichomes prior to abscission. Note constricted base of trichome - where abscission will occur.
Populus deltoides Stem showing resin secreted by stipular bud scales.
Populus deltoides Adaxial side of stipular bud scale with newly-secreted resin.
Populus deltoides Cross section of stipular buds scales - dark adaxial epidermis is composed of resin secretory cells.
Populus deltoides higher magnification of adaxial surface of stipular bud scale. Dark cells are resin-secreting epidermis, light line above epidermis is cuticle pushed off by secretory product.
Populus deltoides bud cross section with stipular bud scales and young leaf lamina
Populus deltoides higher magnification. Structures with dark stained adaxial epidermis is stipular bud scales.
Populus deltoides bud anatomy (from Curtis & Lersten, Amer. J. Bot. 61:835-845. 1974) Fig. 1 represents dissected terminal bud (in cross section in Fig. 3). Fig. 2 represents dissected axillary bud.
Populus deltoides leaf tooth clearing. Tooth tip is terminated by a resin gland.
Populus deltoides 1 um paradermal section of leaf tooth showing resin secreting cells.
Populus tremuloides resin glands on leaf teeth. These produce only small amounts of resin.
Salix lucida stem, leaf margin and stipules with resin glands (from Curtis and Lersten, Amer. J. Bot. 67:1289-1296. 1980).
Salix lucida adaxial view of stipule with resin glands.
Salix lucida leaf lamina margin with resin glands.
Salix lucida leaf margin resin gland (SEM) secreting a strand of resin.
Populus grandidentata extra floral nectaries on young leaf (from Curtis & Lersten. Amer. J. Bot. 65:10http://pix.botany.org/set03/03-1010).
Populus grandidentata leaf with ant feeding on extra floral nectaries.
Populus grandidentata longitudinal section of extra floral nectary. Note abundant phloem.
Populus grandidentata secreting extra floral nectaries.
Populus tremuloides extra floral nectaries. Only small quantities of nectar are secreted (if any).
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