Effects Of Boron And Strigolactones On The Growth And Development Of Pea

Pea(Pisam sativam L.)is one of the most important edible legume crops in China.It’s a multi-purpose crop that integrates grain production,fresh vegetables,food processing and other uses,with high nutritional value and economic value.In production,it is often used to control the plant type of pea by topping or controlling the growth of lateral branches,so as to increase the yield.Boron(B)as one of the essential trace elements for plants,plays an important role in plant growth and development.Boron deficiency restricts plant growth,resulting in reduced yield,and even no harvest in severe cases.Studies have shown that boron plays an important role in regulating plant apical dominance.Strigolactone(SL)as a new plant hormone,can inhibits plants branching,inhibits plants branching by artificial application of SL analogues,and increase crop yields such as rice,soybean and pea.It is speculated that boron and SL may interact with each other to regulate plant branching and yield.Two pea cultivars ‘PS-37’ and ‘PS-99’ were treated with different concentrations of boron,exogenous SL,strigolactone inhibitor(Tis-108),de-topping,and exogenous SL and its inhibitors.By observing the aboveground morphology,axillary buds and root growth of pea,the effect of the interaction of boron and strigolactone on the growth and development of pea was studied.Thus,it provides a theoretical basis for the efficient use of fertilizer and hormones in agriculture,which is conducive to the increase of agronomic income and the development of precision agriculture.The main experimental results are as follows:(1)When supply normal boron(B25),the plants of two pea cultivars ‘PS-37’ and‘PS-99’ grew well,the axillary buds were small or almost non-growing.Under boron deficiency(B0),the plant height and internode spacing of two pea cultivars ‘PS-37’and ‘PS-99’ were shorter,more axillary buds germinated in leaf axils,root system was short,thick and dark,and the upper leaves of the plants gradually yellowed,and the terminal buds gradually appeared boron deficiency phenomena such as wilting with the increase of culture time.The total root length of B0 plant decreased significantly,the total root surface area and total volume decreased significantly,and the average root diameter increased significantly.There are differences in sensitivity to boron among different varieties or plants,among which ‘PS-99’ is more sensitive to boron.The results showed that boron played an important role in the growth and development of pea and participated in the regulation of plant apical dominance.(2)After treated with exogenous SL,the development of axillary buds of B0 peas was significantly inhibited,and the number and length of axillary buds were significantly reduced.With the increase of SL concentration,the inhibition effect of axillary buds was enhanced: 0.5 mg/L SL partially inhibited the development of lateral buds of B0 plants,while 1.5 mg/L completely inhibited the development of lateral buds.In addition,different concentrations of SL had the most significant inhibitory effect on the axillary buds of the second node of pea plants.Different concentrations of SL had no significant effect on the development of axillary buds of B25 plant,and there was no significant difference among different nodes of axillary buds,which showed a small and undeveloped morphology.The results showed that SL could inhibit the growth of axillary buds of pea under boron deficiency.After treatment with SL synthesis inhibitor(Tis-108),the axillary buds at node 0,1 and 2 of B0 plant elongated significantly,and 0.01 mg/L and 0.05 mg/L Tis-108 significantly promoted the elongation of developed axillary buds in B0.However,0.01 mg/L and 0.05 mg/L Tis-108 had no significant effect on the axillary bud development of B25 plant,and the plant grew well and the apical dominance was obvious.The results showed that if inhibition of SL synthesis under boron deficiency,it could promote the elongation of developed axillary buds.While boron addition inhibited SL synthesis but could not induce the development of immature axillary buds.(3)The growth of axillary buds of B0 plants was significantly inhibited when exogenous SL was applied alone.At the same time,the development of axillary buds at 3 node was recovered to a certain extent after the application of SL+ Tis-108,which showed that the inhibition degree of axillary buds was lower than that of SL alone,but there was no significant difference under B25 condition.After de-topping(QD),the apical dominance was relieved,and the axillary buds of pea showed significant development under B25 condition,and there was no significant difference between B0 axillary bud development and non-topping,which further explained the control effect of boron on apical dominance.On this premise of de-topping,apply SL and Tis-108 at the same time(SL + Tis+ QD),was applied to observe the effect of exogenous SL on axillary bud growth.Under the condition of B25,the development of axillary buds was significantly inhibited by exogenous SL treatment after decapitation,but the phenotype was not completely restored to that of non-topping treatment.Under the condition of B0,there was no significant difference in the development of axillary buds induced by exogenous SL.This shows that after removing the apical bud and breaking the apical dominance,SL can inhibit the axillary bud elongation under the condition of boron addition,while SL can not inhibit the lateral bud elongation under the boron deficiency condition,and its mechanism needs to be further studied.(4)The roots of normal boron(B25)plants were long and thin,white,soft and less secondary lateral roots.The whole root system of boron deficiency(B0)plant was short and thick,the color was yellow and the texture was hard,and the elongation of main root and lateral root of pea plant was obviously inhibited.Under the condition of B0,exogenous Tis-108 inhibited the root elongation of pea plants,and the root system had no obvious thickening phenomenon,but the phenotypic difference of B25 plants was not significant.Under the same boron concentration,the root growth of un-topped(QD)treatment and exogenous SL + Tis treatment was not significantly different from that of the control,but there were significant differences among different boron concentrations,which showed that the root growth was better under B25 condition.This shows that boron and strigolactone jointly participate in the regulation of root growth and have a common effect on the root system.To sum up,boron deficiency inhibited the growth of pea,promoted the development of axillary buds and eliminated the apical dominance.SL inhibits the growth and development of axillary buds of pea,which is related to the regulation of boron on apical dominance.