Abstract
Plantlets of Populus yunnanensis Dode were examined in a greenhouse for 48 h to analyze their physiological and proteomic responses to sustained heat, drought, and combined heat and drought. Compared with the application of a single stress, simultaneous treatment with both stresses damaged the plantlets more heavily. The plantlets experienced two apparent response stages under sustained heat and drought. During the first stage, malondialdehyde and reactive oxygen species (ROS) contents were induced by heat, but many protective substances, including antioxidant enzymes, proline, abscisic acid (ABA), dehydrin, and small heat shock proteins (sHSPs), were also stimulated. The plants thus actively defended themselves against stress and exhibited few pathological morphological features, most likely because a new cellular homeostasis was established through the collaborative operation of physiological and proteomic responses. During the second stage, ROS homeostasis was overwhelmed by substantial ROS production and a sharp decline in antioxidant enzyme activities, while the synthesis of some protective elements, such as proline and ABA, was suppressed. As a result, photosynthetic levels in P. yunnanensis decreased sharply and buds began to die, despite continued accumulation of sHSPs and dehydrin. This study supplies important information about the effects of extreme abiotic environments on woody plants.
Highlights
Global warming, the most typical manifestation of worldwide climate change, is a focus of increasing attention
When exposed to a combination of high temperature and drought, treated plants had a greater number of withered leaves and slightly decreased leaf water content from 0 h to 24 h compared with the controls (0 h), with both of these parameters changing drastically after 24 h (Figure 1B)
Yunnanensis), a common broadleaved deciduous tree of southwestern China, respond to extreme high temperature accompanied by drought, with individual treatments of heat and drought used for comparison
Summary
The most typical manifestation of worldwide climate change, is a focus of increasing attention. Recent studies have provided evidence that the molecular, biochemical, and physiological responses of plants to a combination of abiotic stresses are unique and cannot be directly extrapolated from their responses to each stress applied separately [2]. Because high temperatures can increase evapotranspiration rates [3], warming is usually accompanied by drought; plant growth is limited directly by heat stress or indirectly via water shortage. Drought and heat shock are common stress factors that often reduce crop yield by more than 50% [4]. They are two of the most important abiotic stress factors impacting the natural distributions of woody plants and limiting global ecosystem production [5]
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