Structural Analysis of Nectar-Secreting Sites in the Bracts of Paeonia lactiflora

doi:10.7525/j.issn.1673-5102.2026.05.013

Abstract

Abstract:

Although the bracts of Paeonia lactiflora secrete nectar during the bud stage， their secretory sites lack the external morphological characteristics of typical nectaries. To clarify the structural basis of this phenomenon， this study employed semi-thin and ultra-thin sectioning techniques， combined with light microscopy， transmission electron microscopy， and scanning electron microscopy， to observe the microstructural and ultrastructural features of P. lactiflora bracts at different developmental stages. The results showed that：（1）The bracts comprise the epidermis， hypodermis， ground parenchyma， and vascular bundles. During the leaf-expansion stage， the epidermis， some hypodermal cells， and a few parenchyma cells stained deeply with toluidine blue； at the firm stage， staining in these cells became lighter as nectar was secreted. （2）At the leaf-expansion stage， the internal tissues of the bracts exhibited the ultrastructural features of secretory cells： abundant organelles， dense cytoplasm， and well-developed plasmodesmata， which constitute the structural basis for nectar secretion. （3）Nectar is primarily secreted through stomata， and the secretion process may involve symplastic and apoplastic pathways as well as exocytosis. In conclusion， P. lactiflora bracts do not differentiate into morphologically independent and functionally specialized nectary tissues during development， rather， they achieve nectar secretion through the functional specialization of existing tissues， thereby enriching the diversity of nectary structures in angiosperms.

Key words: Paeonia lactiflora, bracts, nectar secretion, nectary

CLC Number:

Q944.5

Weina GUO, Gang LI, Xiaoli XU, Li ZHAO, Lei CHENG. Structural Analysis of Nectar-Secreting Sites in the Bracts of Paeonia lactiflora[J]. Bulletin of Botanical Research, 2026, 46(5): 927-937.

Figures/Tables 6

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