Phosphate Status Affects Phosphate Transporter Expression and Glyphosate Uptake and Transport in Grand Eucalyptus (Eucalyptus grandis)

Abstract

Soluble phosphate availability is a major limiting factor for plant growth, development, and yield. To assure a constant phosphorous supply, plants employ both high- and low-affinity phosphate acquisition mechanisms. Glyphosate is an herbicide widely used throughout the world, and previous studies have suggested that it can be transported across the plasma membrane via phosphate transporters in herbaceous species. The effects of phosphate status on glyphosate uptake were investigated in the tree grand eucalyptus (Eucalyptus grandisW. Hill ex. Maid.). Eucalyptus grandis’s putative phosphate transporters showed differential gene expression in leaves and roots in response to phosphate limitation. Overall, the expression of high-affinity phosphate transporters increased in phosphate-limiting treatments, particularly in roots. More [14C]glyphosate was absorbed and translocated in phosphate-limiting plants compared with control plants grown in phosphate-replete treatments. In leaf mesophyll protoplast assays, rapid uptake of [14C]glyphosate into protoplasts was observed, and addition of phosphate to the assays competed with [14C]glyphosate uptake. These data indicate that phosphate transporters represent one mechanism of glyphosate uptake inE. grandis. These results have implications for best management practices for weed control and glyphosate application under phosphate application regimes.

Hormetic effect of glyphosate persists during the entire growth period and increases sugarcane yield

“…However, the reason for the leaf P concentration trend in this study is not clear and requires further investigation. To date, it has been reported that phosphate transporters play a role in glyphosate absorption and plants cultivated under limited P availability have more phosphate transporters . Despite this, Cakmak et al .…”

Effect of glyphosate and P on the growth and nutrition of Coffea arabica cultivars and on weed control

“…The increase of PO 4 3− fertilization in soils treated with glyphosate leads to an increase in the availability of the herbicide for absorption by the roots, contributing to the efficiency of glyphosate 11 , 36 , due to the main Pi sorption sites are surfaces of iron and aluminum oxides, misordered aluminum silicates and edges of layer silicates, while the sorption of glyphosate by permanently charged layer silicates appears to be limited 11 , 37 . Therefore, glyphosate may have greater absorption and faster translocation in leaves and roots of plants grown in the absence of Pi 12 . This difference in the glyphosate absorption between the culture media with and without Pi is attributed to the phosphate transporters present, since the expression of the high affinity transporters can increase in the absence of Pi 12 .…”

“…Therefore, glyphosate may have greater absorption and faster translocation in leaves and roots of plants grown in the absence of Pi 12 . This difference in the glyphosate absorption between the culture media with and without Pi is attributed to the phosphate transporters present, since the expression of the high affinity transporters can increase in the absence of Pi 12 . We emphasize that the loss of effectiveness of glyphosate applied via foliar can be reduced when plants are grown in soils with a high Pi content, contributing to the selection of glyphosate resistant weed biotypes 12 .…”

“…Studies focused on understanding the interaction between glyphosate and P and their effects on plants are scarce; therefore, there is a need to conduct studies to verify whether the Pi fertilization, depending on the amount of fertilizer P, influences the selectivity of coffee to glyphosate, inducing different responses in relation to seedling growth and nutrient absorption, as well as weed control (i.e., I. grandifolia and U. decumbens ), as there is evidence that Pi increased glyphosate absorption by the root in Hydrocharis dubia and Salix miyabeana , preventing oxidative stress caused by glyphosate 14 , 18 . In contrast, Eucalyptus grandis plants subject to P deficiency absorbed more 14 C-glyphosate 12 . These divergences may be associated with the physical–chemical characteristics of the spray solution, since the electrical conductivity, pH, surface tension and viscosity can interfere in the droplet spectrum and influence the interaction of the herbicide with the target surface 19 , 20 .…”

“…Glyphosate has a Pi group in its molecule, therefore, numerous factors can influence the sorption and desorption of glyphosate in the soil, including P ion content, as there is a close relationship between glyphosate and Pi sorption capacity by soils, i.e., the sorption mechanisms of Pi and glyphosate are similar, competing with each other for the same soil retention site 12 – 15 . On the other hand, plants absorb P through the cell membrane which is translated by Pi transporters, while glyphosate can enter plants by passive diffusion or via endoplasmic transport system, also using Pi transporters from the cell membrane 14 , 16 .…”