Morphology, Seasonal Variation, and Function of Resin Glands on Buds and Leaves of Populus Deltoides (Salicaceae)

Abstract

When buds form in summer or early fall, modified stipules act as bud scales and their adaxial epidermis secretes a resin that fills the bud. This secretory layer collapses in the dormant bud. Immature leaves, stipules, and leaf primordia occupy the center of the bud; all lack functional resin glands. In spring, stipules of emerging leaves develop an adaxial palisadelike secretory epidermis that becomes more ridged longitudinally in successive stipules. Marginal teeth of the first leaves to emerge are covered with trichomes and lack a secretory epidermis. In successive leaves the teeth become glandular and secrete resin as the lamina unrolls. Later in the season, marginal leaf glands account for much of the resin. Unspecialized hydathodes or extrafloral nectaries occur proximal to each glandular tip. Guttation of water or nectar occurs here through stomata located above a vein ending. On the basis of field observations and a laboratory feeding experiment, the resin seems to function mainly as an insect repellent. It may also reduce water loss from young leaves.

Carbon/Nutrient Balance of Boreal Plants in Relation to Vertebrate Herbivory

“…At Atkasook in northern Alaska experimental defoliation had greatest impact upon regrowth by deciduous species if it was applied in early spring during rapid leaf growth (Fig. If carbon is used for defense of young leaves, it is often the product of late season photosynthesis from the previous year, for example the bud resins of Populus deltoides (Curtis and Lersten 1974). In deciduous species exposed to intense herbivory there is strong selection to minimize the time that leaves remain undefended (Feeny 1970) and to employ nitrogen-based defenses, for example alkaloids or cyanogenic glycosides, which are toxic in extremely small quantities (Dement and Mooney 1974, Feeny 1976, Rhoades and Cates 1976, Prudhomme 1983).…”

Hydathodal leaf teeth of Chloranthus japonicus (Chloranthaceae) prevent guttation‐induced flooding of the mesophyll

“…Some have hypothesized that leaf teeth are not directly physiologically significant to plants. For instance, resin secretions from teeth in Populus deter leaf‐feeding caterpillars (Curtis & Lersten 1974). Also, spinose marginal leaf teeth can impede insects from chewing along the leaf margin (Ehrlich & Raven 1967; Givnish 1979; Brown & Lawton 1991).…”

Plant eco‐devo: the potential of poplar as a model organism

“…Phytochemistry Poplars defend themselves by the production of complex phenolic‐based resins (Curtis & Lersten, 1974; Greenaway et al ., 1992). The balsam poplars, as their name implies, are particularly important resin producers.…”