Surface Canopy Position Determines the Photosystem II Photochemistry in Invasive and Native Prosopis Congeners at Sharjah Desert, UAE

Abstract

<jats:p>Plants have evolved photoprotective mechanisms in order to counteract the damaging effects of excess light in hyper-arid desert environments. We evaluated the impact of surface canopy positions on the photosynthetic adjustments and chlorophyll fluorescence attributes (photosystem II photochemistry, quantum yield, fluorescence quenching, and photon energy dissipation), leaf biomass and nutrient content of sun-exposed leaves at the south east (SE canopy position) and shaded-leaves at the north west (NW canopy position) in the invasive Prosopis juliflora and native Prosopis cineraria in the extreme environment (hyper-arid desert area, United Arab Emirates (UAE)). The main aim of this research was to study the photoprotection mechanism in invasive and native Prosopis congeners via the safe removal—as thermal energy—of excess solar energy absorbed by the light collecting system, which counteracts the formation of reactive oxygen species. Maximum photosynthetic efficiency (Fv/Fm) from dark-adapted leaves in P. juliflora and P. cineraria was higher on NW than SE canopy position while insignificant difference was observed within the two Prosopis congeners. Greater quantum yield was observed in P. juliflora than P. cineraria on the NW canopy position than SE. With the change of canopy positions from NW to SE, the reduction of the PSII reaction center activity in the leaves of both Prosopis congeners was accelerated. On the SE canopy position, a significant decline in the electron transport rate (ETR) of in the leaves of both Prosopis congeners occurred, which might be due to the blockage of electron transfer from QA to QB on the PSII acceptor side. On the SE canopy position; Prosopis leaves dissipated excess light energy by increasing non-photochemical quenching (NPQ). However, in P. cineraria, the protective ability of NPQ decreased, which led to the accumulation of excess excitation energy (1 − qP)/NPQ and the aggravation of photoinhibition. The results also explain the role of different physiological attributes contributing to invasiveness of P. juliflora and to evaluate its liaison between plasticity of these characters and invasiveness.</jats:p>

Global Invasion Risk Assessment of Prosopis juliflora at Biome Level: Does Soil Matter?

“…Also, P. juliflora has several adaptive features that enable it to grow well and even flourish in very poor dry hot desert habitats that are commonly considered to be unsuitable for the dominance of many other plant species [ 11 , 12 , 13 , 74 ] For example, the deep taproot of this species allows it to secure its water requirements during dry seasons and hence to invade the dry arid lands [ 74 ]. In addition, P. juliflora was able to tolerate high sun intensity and temperatures of the hyper-arid environment of the Gulf region by avoiding permanent damage of the photosynthetic apparatus that happened by lowering PSII efficiency and dissipating extra light energy through the increase of non-photochemical quenching [ 12 ]. Furthermore, the intrinsic water-use efficiency of P. juliflora was significantly greater than in the congeneric native P. cineraria in the arid deserts [ 13 ].…”

“…Such a change in soil texture would exacerbate the invasion rate of P. juliflora in such arid deserts. Moreover, P. juliflora gains more advantages over its native competitors, making it spread faster in the infested countries [ 12 , 13 ]. The investigations conducted in the Sultanate of Oman, one of the top threatened countries in the desert biome according to our models, indicated that P. juliflora germinated faster and greater, even under stress conditions, such as heat and drought, as compared with its native congener P. cineraria [ 84 ].…”

“…It is naturalized and invaded several tropical and sub-tropical regions worldwide at an alarming rate [ 1 , 9 ]. In addition, this species is surviving and thriving in the harsh conditions of the hyperarid Arabian deserts, where annual average rainfall is less than 100 mm and average temperatures reach above 40 °C during summer [ 10 , 11 , 12 , 13 , 14 , 15 ]. The introduction was for different purposes, including for example, combating desertification and land reclamation, greening deserts, and its utilization as sources of animal feed, especially pods that represent a considerable part of goats’ diet, biofuel, timber, shelter, building material and furniture for local farmers [ 1 , 8 , 16 ].…”

Allelopathic Potential of Aqueous Extract from Acacia melanoxylon R. Br. on Lactuca sativa

“…Several authors indicated that it is extremely difficult to separate the growth and physiological secondary effects afrom the primary impacts caused by allelochemicals. However, the secondary impacts led to the disruption of cell differentiation, plant water status, water uptake, respiration, signal transduction, photosynthesis and enzyme function [ 3 , 6 , 7 , 10 , 17 , 26 ].…”

Secondary Metabolites, Ferulic Acid and p-Hydroxybenzoic Acid Induced Toxic Effects on Photosynthetic Process in Rumex acetosa L.

“…Chlorophyll fluorescence quenching and non-photochemical quenching were calculated as demonstrated by Kramer et al [ 24 ], and Bilger et al [ 25 ]. The excess photon energy of the PSII reaction center was calculated as (1−qP)/NPQ [ 18 , 22 , 26 , 27 ].…”