In: Phyton 59, Fasc. 1 (2019): S. 119-129 DOI: 10.12905/0380.phyton59-2019-0119 Published online on 19 Dezember 2019

Formation of successive cambia and structure of secondary xylem in Dicranostyles ampla and Maripa nicaraguensis (Convolvulaceae)

Roger Moya

Key words: Cambial variant, multiple cambia, successive cambia, secondary xylem, woody lianas, scandent shrubs; Dicranostyles ampla, Maripa nicaraguensis, Erycibeae, Convolvulaceae.

Summary
Moya R., Gondaliya A. D. & Rajput K. S. 2019. Formation of successive cambia and structure of secondary xylem in Dicranostyles ampla and Maripa nicaraguensis (Convolvulaceae). – Phyton (Horn, Austria) 59 (1–2): 119–129, with 5 figures.*
Lianas are important components of the forest ecosystem and are well adapted by external (morphological) and internal (anatomical) modifications of organs for successful climbing habit. Morphological adaptations include various types of tendrils, hooks, spines etc., while internal modifications include abundance of parenchyma, vessel dimorphism, large rays, and variant secondary growth. The main aim of the present study is to examine pattern of secondary growth, structure and development of the secondary xylem and phloem in the two lianas Dicranostyles ampla Ducke and Maripa nicaraguensis Hems l. of the tribe Erycibeae. Both species show successive rings of the secondary xylem alternating with the phloem. The first successive cambium initiates as small segments that get interconnected and form a complete ring and differentiate bidirectionally. Functionally inverse cambia initiate from the conjunctive tissue on the inner margin of earlier formed xylem rings. In both species, the secondary xylem is diffuse porous with indistinct growth rings and shows co-occurrence of wide and narrow vessels, sclerotic tyloses in vessels, tracheids, fibre tracheids, ray and axial parenchyma, while islands of unlignified parenchyma are absent. Transitional forms between fibriform vessels and tracheids can be observed in both species. Bordered pits on the lateral walls occur in M. nicaraguensis and are reported for the first time in Convolvulaceae. The structure of the secondary xylem is compared with the available literature on the tribe Ipomoeeae.