Physiological Characterization of Young 'Hass' Avocado Plant Leaves Following Exposure to High Temperatures and Low Light Intensity.

Or Shapira,Lior Rubinovich,Simon Chernoivanov,Itamar Neuberger,Shay Levy

doi:10.3390/plants10081562

Or Shapira, Lior Rubinovich + Show 3 more

Open Access

https://doi.org/10.3390/plants10081562

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Abstract

The worldwide demand for avocados has resulted in the planting of millions of young plants each year. However, global warming, resulting in high temperatures, sensed as heat stress, may severely damage these new plantings. The objective of this study was to assess the risks of heat stress on young avocado plants. We aimed to characterize different physiological parameters of young ‘Hass’ plant leaves following exposure to high temperatures under low light (LL) intensity and to pinpoint the temperature threshold for significant heat stress damage in these plants. To this end, young potted plants were subjected to different temperature gradients in a controlled-climate chamber. Minor and severe leaf damage was apparent in plants subjected to the 51 °C and 53 °C treatments, respectively. Minor and vast reductions in optimal quantum yield efficiency of photosystem II (Fv/Fm) values were observed in plants subjected to 51 °C and 53 °C, respectively. Heat stress treatments significantly reduced CO2 assimilation in plants subjected to 49 °C and higher temperatures. Stomatal conductance to water vapour and substomatal internal CO2 concentration were less sensitive to the heat treatments. These results imply that the heat damage threshold for young avocado plants under LL conditions is between 49 °C and 51 °C, whereas at 53 °C, severe and irreversible leaf damage occurs.

Highlights

Over the last decade, changing climate patterns have been associated with global warming [1]
Net carbon assimilation may decline due to various processes such as increased photorespiration, increased mitochondrial respiration, inactivation of Rubisco and decreased activity of photosystem II [5,6]
Heat stress may reduce the optimal quantum yield of photosystem II (Fv/Fm) ratio, which leads to significant reductions in photosynthesis [3,8]

Summary

Introduction

Over the last decade, changing climate patterns have been associated with global warming [1]. Plants may be severely damaged by very high temperatures, sensed as heat stress [2]. Heat stress may impair crucial physiological processes in the plant, namely photosynthesis and respiration rates, stomatal conductance and leaf water potential homeostasis [4]. Stomatal conductance may be elevated or reduced, depending on the plant species and the heat stress conditions [7]. Other direct effects of heat stress, such as increased fluidity of the thylakoid membranes, increased reactive oxygen species (ROS) production, inactivation of enzymes, loss of membrane integrity, inhibition of protein regulations and protein degradation may lead to severe injuries to different plant tissues [9]. As heat stress may severely limit the productivity of various commercially important crops, global warming has potential calamitous impacts on global food security [3,11]

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