Chitosan Oligosaccharide Addition to Buddhist Pine (Podocarpus macrophyllus (Thunb) Sweet) under Drought: Reponses in Ecophysiology and δ13C Abundance

Chunxia He,Yan Zhao,Jun Gao,Jinsong Zhang

doi:10.3390/f11050526

Abstract

Climate warming induces the necessity to increase the drought resistance of shade-obligate juvenile trees in sub-tropical forests. Chitosan oligosaccharide (COS) is a biopolymer derived from the marine resource that has attracted accumulative attention to induce and promote a plant’s resistance to abiotic stress. Buddhist pine (Podocarpus mascrophyllus (Thunb)Sweet) seedlings were cultured as the model material whose natural distribution in sub-tropical areas of China has suffered severe summer drought events in the last 113 years. A split-block design was conducted with a simulated drought event (drought vs. irrigated control), the COS addition, and two samplings at the ends of drought and re-watered treatments. The COS addition increased the resistance to drought by inducing a starch allocation towards roots where δ13C abundance and antioxidant enzyme activities were upregulated. The COS addition can promote biomass allocation to roots and increase the number of new roots. The COS addition to drought-treated Buddhist pine seedlings resulted in robust diameter growth. Therefore, COS is an available polymer to promote the resistance of Buddhist pine to drought. More work is suggested to clarify the dose of COS addition that can induce a prominent response of biomass accumulation and carbohydrate metabolism.

Highlights

Climate change brings about increasing drought events that shape the global forest distribution and changes the within-forest structure in all biomes [1]
chitosan oligosaccharide (COS) addition at the seedling height and at the second sampling, followed by the irrigated control treatment second sampling resulted in a lower height and root-collar diameter (RCD)
Our results revealed that the activities of these enzymes were all promoted by the COS addition in Buddhist pine seedlings

Summary

Introduction

Climate change brings about increasing drought events that shape the global forest distribution and changes the within-forest structure in all biomes [1]. Sub-tropical forests exchange more carbon dioxide (CO2 ) with the atmosphere than any other vegetation type; they are facing the most challenging droughts on the planet [2]. The pattern of precipitation shift exposes sub-tropical forests to foreseeing frequent drought events that may impair carbon (C) assimilation, even to the extent of vegetation dieback [3]. The functional composition of sub-tropical forests has been reformed from tall and strong dominant trees towards smaller and denser wooded dwarfs. During this process, the mortality of trees in sub-tropical forests has continuously occurred directly, or partially, due to water-deficit events. People are helpless to cope with the drought impact on forest trees, even though it can be foreseen to come in high frequency

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Results

Conclusion