Axial and Radial Spatial Patterns of Non-Structural Carbohydrates in Cycas micronesica Stems.

Thomas Marler

doi:10.3390/plants7030049

Abstract

The pachycaulous stem of arborescent cycad species exhibits unique traits and has received limited research. To date, nothing is known about the axial and radial spatial patterns of non-structural resources within cycad stems. Cycas micronesica K.D. Hill stem tissue was collected from apical and basal axial positions of ca. 100-cm tall plants to serve as two axial regions; and from pith, vascular, and cortex tissues to serve as three radial regions. Starch and four free sugars were quantified. These stems contained more starch than any of the individual sugars, and sucrose concentration exceeded that of fructose and glucose, which exceeded that of maltose. Total non-structural carbohydrate was least in basal vascular tissue (225 mg·g−1) and greatest in apical pith tissue (379 mg·g−1). Axial differences in NSC concentrations were negligible but radial differences were substantial. These results combine with past research to validate the non-woody cycad stem contains copious nonstructural resources available for deployment to ephemeral sinks during critical times of need.

Highlights

Cycas micronesica is an arborescent cycad species from several island groups in Micronesia [1].The tree is one of 350 cycad species [2] that comprise the most threatened group of plants worldwide [3,4]
Glucose, maltose, and starch exhibited the lowermost concentrations in vascular tissues, with pith concentrations generally exceeding those of cortex
The stoichiometric relationship between free sugars and starch was calculated as the quotient sugars/starch

Summary

Introduction

Cycas micronesica is an arborescent cycad species from several island groups in Micronesia [1]. The tree is one of 350 cycad species [2] that comprise the most threatened group of plants worldwide [3,4]. Guam in 2003 [5,6], and this invasion was the start of several biological threats that have caused widespread mortality of the tree species [7]. The use of large C. micronesica stem cuttings as propagules was evaluated to determine if the approach could be employed to rescue trees from construction sites on Guam [10]. The findings indicated that more research to determine the potential causes of limited propagation success was required before implementing the procedure on a large scale [11].

Methods

Results

Conclusion