Colleters, Extrafloral Nectaries, and Resin Glands Protect Buds and Young Leaves of Ouratea castaneifolia (DC.) Engl. (Ochnaceae)

Buds usually possess mechanical or chemical protection and may also have secretory structures. We discovered an intricate secretory system in Ouratea castaneifolia (Ochnaceae) related to the protection of buds and young leaves. We studied this system, focusing on the distribution, morphology, histochemistry, and ultrastructure of glands during sprouting. Samples of buds and leaves were processed following the usual procedures for light and electron microscopy. Overlapping bud scales protect dormant buds, and each young leaf is covered with a pair of stipules. Stipules and scales possess a resin gland, while the former also possess an extrafloral nectary. Despite their distinct secretions, these glands are similar and comprise secreting palisade epidermis. Young leaves also possess marginal colleters. All the studied glands shared some structural traits, including palisade secretory epidermis and the absence of stomata. Secretory activity is carried out by epidermal cells. Functionally, the activity of these glands is synchronous with the young and vulnerable stage of vegetative organs. This is the first report of colleters and resin glands for O. castaneifolia. We found evidence that these glands are correlated with protection against herbivores and/or abiotic agents during a developmental stage that precedes the establishment of mechanical defenses.

Regarding the structure and possible function of the columella in seed cones of Callitroideae (Cupressaceae): a morpho-anatomical approach

‘Columella’-named structures in seed cones of callitroid Cupressaceae were investigated. In the past, the term columella was used for different structures, which should not be summarised and treated under the same name. We suggest that all apices should be called columella, which exclusively represent the prolonged tip of the cone axis and do not reach the periphery of the seed cone and do not take part in it. The three distal lobes in Fitzroya Lindl. represent a sterile, strongly reduced, distal whorl of cone scales and not naked nucelli or resin glands as suggested in former studies. They should not be termed columella. The columellae and also the three lobes in Fitzroya may play a role within the pollination process and possibly in the chemical defence against pathogens. The columella, as it is defined here, is not restricted to the Callitroideae and is also present in other Cupressaceae, including Cupressus L. and Thujopsis Siebold & Zucc.