Effects Of Low Potassium Stress On Peanut Growth And Nutrient Uptake Utilization In Peanut

Potassium is one of the three major nutrients in plants and plays an important role in various physiological and metabolic processes such as osmotic regulation of cells,activation of enzymes and ion balance.The soil in the peanut production area is mainly aeolian sandy soil and sandy loam soil.Insufficient available potassium content in the soil has become an main factor restricting peanut yield and quality.Therefore,it is of great significance to carry out research on peanut potassium deficiency.In this study,four peanut varieties HY20,HY22,NH18,NH19 were used as materials,and the potting method was used to study effects of low potassium stress(available potassium,57.0 mg/kg)on plant morphology,dry matter accumulation,leaf gas exchange,and chlorophyll fluorescence characteristics,protective enzyme activity,nutrient absorption and utilization in peanut.The main findings are as follows:1.The effect of low potassium stress on peanut plant morphology and dry weight is mainly manifested in the late growth stage.At the flowering stage(S1),there was no significant difference in morphological indexs and dry matter accumulation between low potassium treatment and control.After the pod setting period(S2),under low potassium stress,root length,root surface area,and root volume are lower than those under normal potassium,and the dry weight of each organ is also lower than those under normal potassium.There was no significant difference between main stem height and side branch length between low potassium treatment and the controls during the whole growth period.2.Under low potassium stress,the net photosynthetic rate(Pn),stomatal conductance(Gs)and intercellular CO2 concentration(Ci)were significantly reduced,while the stomatal limit value(Ls)was significantly increased,indicating that the decrease in leaf photosynthetic rate was caused by stomatal factor constraints.Low potassium stress leads to a decrease in chlorophyll content,maximum fluorescence(Fm),variable fluorescence(Fv)and maximum photochemical efficiency(Fv/Fm),but an increase in basal fluorescence(Fo),indicating that the activity of the photosystem ? reaction center decreases under low potassium stress;Under low potassium stress,the actual photochemical efficiency(?PSII),electron transfer rate(ETR)and photochemical quenching coefficient(q P)decreased,and non-photochemical quenching(NPQ)increased,indicating that the photosynthetic mechanism is hindered in capturing,converting and transferring light energy.Increased heat dissipation leads to more loss of light energy,resulting in decreased photosynthetic performance of leaves.This indicates that the decline of peanut photosynthetic capacity under low potassium stress is affected by the combined effects of stomata and non-stomata factors.3.Compared with controls,under low potassium stress,the malondialdehyde(MDA)content,superoxide dismutase(SOD)and peroxidase(POD)activities increased by 11.7% ~ 20.9%,23.4% ~ 39.4and 11.1% ~ 42.8%,respectively.The content of soluble protein in leaves increased by 16.2% ~ 45.5% under low potassium stress,indicating that peanut can maintain normal osmotic adjustment ability through soluble protein,thus showing a certain adaptability to low potassium stress.4.The K~+ content of roots,stems,leaves and pegs decreased significantly under low potassium stress,which decreased by 41.1 ~ 66.1%,23.5% ~ 73.8%,23.2% ~ 56.6% and 22.7% ~ 32.9%,respectively.The falling range gradually increased in the stems and leaves as the growth period,while the pods gradually decreased.During the flowering stage,the potassium distribution ratio of roots and stems under low potassium stress is lower than controls,and the plant potassium tends to be distributed to leaves;after the pod-setting period,the potassium distribution ratio of roots,stems and leaves is lower than controls under low potassium stress potassium,and the distribution ratio of pods and pegs is significantly higher than controls,indicating that the plant potassium tends to be distributed to pods and pegs.The K+ content of the plant decreased with growth period,and the potassium utilization efficiency gradually increased.Under low potassium stress,potassium utilization efficiency increased by 25.6% ~ 44.4% compared with that controls.Under low potassium stress,the Na+ content of the root increased significantly by 56.0% ~ 110.2%,the sodium content of the stem also increased,and the calcium content of the leaves increased by 2.6% ~ 22.1%,but the nitrogen and phosphorus content of each organ of the plant were not significant difference.The rise of Ca2+ and Na+ content under low potassium stress suggests that they have a substitution effect with K+,which improves the adaptability of peanut to low potassium stress.5.The yield of peanut per plant decreased by 13.3%~22.9% under low potassium stress;Meanwhile,the yield traits including pods per plant,mature pods per plant,mature pods weight,100-pod weight,and 100-seed weight were also reduced by 7.5% ~ 21.3%,14.0% ~ 20.2%,16.6% ~ 23.0%,9.5% ~ 14.6%,10.0% ~ 19.0%.