Improvement in light utilization and shoot growth in Hymenaea stigonocarpa under high CO 2 concentration attenuates simulated leaf herbivory effects

Renata A Maia,Geraldo W Fernandes,João Paulo Souza,Advanio I S Silva

doi:10.1590/0102-33062019abb0149

Abstract

ABSTRACT This study evaluated the photochemical responses of photosystem II and growth of Hymenaea stigonocarpa under CO2-enriched conditions with exposure to simulated herbivory events. After herbivory simulation in two distinct parts of the stem of plants (apex and base), chlorophyll a fluorescence, chlorophyll index, growth, extrafloral nectary density, leaf mineral nutrition, and biomass production were evaluated. Plants of H. stigonocarpa grown under high [CO2] after simulated herbivory in the apical part of the stem had higher electron transport rate, effective quantum yield of photosystem II, and chlorophyll contents. However, simulated herbivory in the basal portion of plants grown under high [CO2] increased plant height, branch and root length, leaf number, leaf area, node number, and leaf expansion rate. In conclusion simulated herbivory at the basal portion and high [CO2] induce positive responses in H. stigonocarpa, leading to the allocation of biomass to vegetative parts related to the capture of resources such as water and light. Apical leaves could compensate for the elimination of part of their leaf blades by increasing their photosynthetic yield. Thus, the increase of [CO2] attenuated the adverse effects of leaf removal on H. stigonocarpa plants by inducing photosynthetic improvement and growth after the loss of leaf tissue.

Highlights

Cerrado, considered a biodiversity hotspot, presents a high degree of endemism, which, is threatened
This study aimed to identify the photochemical responses of PSII, chlorophyll content, foliar nutrients, morphometry, and extrafloral nectaries (EFNs) production in H. stigonocarpa growing under ambient or elevated [CO2] in the atmosphere and subjected to simulated herbivory on the leaves of the basal and apical portions of the stem
Simulated herbivory contributes to obtaining physiological responses of plants after damage and the resultant effects of biotic and abiotic interactions (Tscharntke et al 2001; Scott et al 2019).The increase of F0 in the leaves of plants grown in ambient [CO2] and subjected to simulated herbivory at the basal or apical portion of the stem is possibly related to the existence of damage at the PSII reaction center or to the reduction of energy transfer capacity of excitation from the light collecting system to the reaction center (Baker & Rosenqvist 2004)

Summary

Introduction

Cerrado, considered a biodiversity hotspot, presents a high degree of endemism, which, is threatened. In addition to the expansion of agricultural frontiers, changes in the climate, such as increased CO2 concentration ([CO2]) in the atmosphere, drought intensification, and high temperatures, have threatened this ecosystem. Understanding the vulnerability of Cerrado vegetation to climate change requires the investigation of the effect of high [CO2] on plant growth and its interactions with biotic and abiotic factors. Several studies have shown that high [CO2] results in increased net photosynthesis, the accumulation of nonstructural carbohydrates, and decreases of leaf nitrogen content, stomatal conductance, and transpiration (Ainsworth & Rogers 2007; Stiling & Cornelissen 2007; Wang et al 2012; Bunce 2014; Lewis et al 2015; Xu et al 2016).

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