Phosphorous Application Improves Drought Tolerance of Phoebe zhennan

Abstract

Phoebe zhennan (Gold Phoebe) is a threatened tree species in China and a valuable and important source of wood and bioactive compounds used in medicine. Apart from anthropogenic disturbances, several biotic constraints currently restrict its growth and development. However, little attention has been given to building adaptive strategies for its conservation by examining its morphological and physio-biochemical responses to drought stress, and the role of fertilizers on these responses. A randomized experimental design was used to investigate the effects of two levels of irrigation (well-watered and drought-stressed) and phosphorous (P) fertilization treatment (with and without P) to assess the morphological and physio-biochemical responses of P. zhennan seedlings to drought stress. In addition, we evaluated whether P application could mitigate the negative impacts of drought on plant growth and metabolism. Drought stress had a significant negative effect on the growth and metabolic processes of P. zhennan. Despite this, reduced leaf area, limited stomatal conductance, reduced transpiration rate, increased water use efficiency, enhanced antioxidant enzymes activities, and osmolytes accumulation suggested that the species has good adaptive strategies for tolerating drought stress. Application of P had a significant positive effect on root biomass, signifying its improved water extracting capacity from the soil. Moreover, P fertilization significantly increased leaf relative water content, net photosynthetic rate, and maximal quantum efficiency of PSII under drought stress conditions. This may be attributable to several factors, such as enhanced root biomass, decreased malondialdehyde content, and the up-regulation of chloroplast pigments, osmolytes, and nitrogenous compounds. However, P application had only a slight or negligible effect on the growth and metabolism of well-watered plants. In conclusion, P. zhennan has a strong capability for drought resistance, while P application facilitates and improves drought tolerance mostly through physio-biochemical adjustments, regardless of water availability. It is imperative to explore the underlying metabolic mechanisms and effects of different levels of P fertilization on P. zhennan under drought conditions in order to design appropriate conservation and management strategies for this species, which is at risk of extinction.

Impact of phosphorus application on drought resistant responses of Eucalyptus grandis seedlings

“…Previous studies have suggested that P uptake by plant roots further decreases under water deficit conditions (Cramer et al , Sardans and Penuelas ) and that plant growth is dependent on the availability of P. Our findings also revealed that height, stem diameter, leaf area, stem and leaf biomass and LRWC were significantly lower in drought‐stressed seedlings than those in with well‐watered plants which indicates strong sensitivity of E. grandis to water deficits in the soil (Tables and ). The present findings are in line with other studies that were conducted on different forest tree species (Oliveira et al , Liu et al , Tariq et al , ). However, root biomass was similar in the drought‐stressed and well‐watered plants, regardless of P application.…”

“…It has already previously been found that the demand for P is high during the first year of growth, while the demand is lower in later stages, because of internal recycling (Fernandez et al ). The present findings are in line with the results of previous studies (Cicek et al ), but contradicted the results of other studies conducted on other forest tree species (Liu et al , Tariq et al , ). The lack of effect of P fertilization under drought indicates that P uptake was more limited and difficult under low moisture content in the soil than in well‐watered conditions and demonstrates that different species respond differently to P fertilization because they have varied physiological adjustments, nutrient availability and interaction and soil physical properties.…”

“…These changes lead to over‐production of reactive oxygen species (ROS) and eventually photoinhibition (Parvaiz and Satyawati ). These ROS, which include superoxide ions (O 2 •– ) and hydrogen peroxides (H 2 O 2 ) under drought stress, result in considerable damage to proteins, DNA and lipids, thereby inhibiting plant growth (Tariq et al ). In response to water deficit stress plants have evolved different protective mechanisms to reduce the damage to photosynthetic machinery from the over‐generation of ROS and photoinhibition.…”

“…However, the effects of P application on leaf photosynthetic apparatus, osmolyte accumulation, antioxidant system and nitrogenous compound accumulation under drought stress remain unclear. Different studies have suggested that P fertilization improves the drought tolerance of forest tree species by means of physiological and biochemical adjustments (Liu et al ; Tariq et al , ). However, in any of those antecedents, plants responded to P fertilization by increasing growth.…”

Role of nitrogen supplementation in alleviating drought‐associated growth and metabolic impairments in Phoebe zhennan seedlings

“…Moreover, the stress effect also depends on a plant's ability to improve water uptake with minimum loss (Chaves et al, 2003). For instance, some forest trees maximize water uptake by developing deeper roots, reducing leaf area and/or stomatal conductance, increasing osmolyte concentrations and implementing other modifications at the leaf level (Munné -Bosch and Alegre, 2004;Tariq et al, 2017).…”