Distribution Dynamics and Roles of Starch in Non-photosynthetic Vegetative Organs of Santalum album Linn., a Hemiparasitic Tree

Xiu Ren Zhou,Jing Tian,Ning Nan Zhang,Yi Min Zhao,Gui Fang Xu,Da Ping Xu,Lei Dai

doi:10.3389/fpls.2020.532537

Abstract

Allocation dynamics of stored starch plays essential roles in the development and growth of trees. Previous studies focused on the dynamics and the characteristics of starch in autotrophic trees. However, although starch granules have been detected in the organs or tissues of some parasitic plants, studies on the allocation dynamics and roles of storage starch in them are limited. Therefore, we determined and estimated the allocation dynamics and roles of starch in Santalum album Linn., a hemiparasitic tree, using morphological and physiological methods. Our findings showed abundant starch in the stem and root of S. album at the early seedling stage. Although S. album seedlings attached to the host showed no significant changes in starch levels throughout the experiment, unattached and host-removed seedlings exhibited a gradual decrease in the starch content over time. When the starch content of unattached seedlings was less than 1%, they started to die. Starch accumulated to high levels in developing and active haustoria; however, starch levels were low in the inactive haustoria. The present study suggests that starch may provide energy to seedlings that have no host, allowing them to survive during the unattached phase, thus increasing their chance to attach to host roots by extending their survival duration. In addition, we speculate that storage starch is potentially involved in the development of haustoria and in the physiological processes of S. album related to the absorption and transportation of water and nutrients from its host.

Highlights

IntroductionUnder abiotic stress conditions, such as low/high temperature or drought, starch is degraded, generating osmotically active compounds and energy, which are used to ensure plant survival (Levitt, 1980; Guehl et al, 1993; Uemura and Steponkus, 2003; McDowell et al, 2008; Adams et al, 2009; Sala et al, 2010; Villar-Salvador et al, 2015)
Starch is the most critical long-term energy storage carbohydrate in plants
We focused on the qualitative visualization and the quantitative determination of starch allocation dynamics in non-photosynthetic organs of S. album and on the potential roles of starch in this parasitic plant

Summary

Introduction

Under abiotic stress conditions, such as low/high temperature or drought, starch is degraded, generating osmotically active compounds and energy, which are used to ensure plant survival (Levitt, 1980; Guehl et al, 1993; Uemura and Steponkus, 2003; McDowell et al, 2008; Adams et al, 2009; Sala et al, 2010; Villar-Salvador et al, 2015). Storage starch plays a crucial role in ensuring the growth and development of plants in the absence of photosynthesis or under stress conditions (McDowell et al, 2008; Sala et al, 2010; Villar-Salvador et al, 2015)

Methods

Results

Conclusion