Differences In Zinc And Boron Deficiency Between Two Navel Orange Grafted Plants

In our country,the citrus-growing regions are mostly located in the southern red soil region where is rainy.This is easy to cause the deficiency of boron,zinc,magnesium,calcium and the other elements because of the serious nutrient loss and the discomfort soil PH.Deficiency of boron and zinc are very prominent in many nutrient deficiency symptoms.Predecessors who study the deficiency of boron and zinc mostly focus on the root stock,while all commercial citrus are grafted trees,so the study of grafted seedlings are conducive to provide the basis for solving the problem of the deficiency of the multi elements via to choose the appropriate root stock to inarch.Therefore,in the present study,the methods of sand culture were used to investigate the sensitivity of ‘Newhall' navel orange grafted on trifoliate orange and Carrizo citrange under B and Zn deficiency.The results are as following:1.The comparison of two different kinds of root stock in zinc deficiency1)The growth indicators: the leaves of ‘Newhall' navel orange grafted on Carrizo citrange show obvious etiolation symptoms and the trifoliate orange were not obvious under zinc deficiency.In addition,the plant height and internode length of the Carrizo citrange decreased significantly,the trifoliate orange was not significant.2)Physiological characteristics: under the zinc stress condition,the content of Chl a,Car and Chl.(a+b)were decreased 37.44%,29.42% and 44.18%,respectively,in citrange grafted plants,while no significant change in trifoliate orange grafted plants;that led to the lower amplitude of photosynthetic rate of Carrizo citrange was much higher than that of trifoliate orange.Zinc stress decreased the POD and CAT activities in two grafted combinations,however,citrange grafted plants sereve decreased the activities of them.Moreover,the activity of SOD was decreased 12.19% in citrange grafted plants,whereas no significantly changes in trifoliate orange grafted plants.3)The content of mineral elements: after zinc deficiency treatment,the zinc content of each part of‘Newhall' navel orange grafted on trifoliate orange and Carrizo citrange were decreased,but the decreased magnitude of zinc content of Carrizo citrange was higher than trifoliate orange.However,the zinc content of young leaf and rootstock stem were not significantly affected in trifoliate orange grafted plants,whereas the zinc content of citrange grafted plants in these two part were reduced 38.27% and 38.24%,respectively.From these physiological indexes and the mineral elements content of each part,comparing to the Carrizo citrange,the trifoliate orange showed a stronger ability to resist zinc deficiency.2.The comparison of two different kinds of root stock in boron deficiency1)The growth indicators: the leaves of ‘Newhall' navel orange grafted on Carrizo citrange show serious etiolation,veins cork,even burst signs symptoms and the trifoliate orange were only showed the etiolation symptoms under zinc deficiency.In addition,the total dry weight of trifoliate orange was significantly reduced by 24.46 % under boron deficiency,and there was not obvious changes about that of Carrizo citrange.2)Physiological characteristics: the decreased magnitude of Chb and Chl.(a+b)content of the leaves of ‘Newhall' navel orange grafted on trifoliate orange was lower than that of Carrizo citrange,and the photosynthetic pigment content was better than that of Carrizo citrange.Under the Zinc stress condition,the value of Pn was decresed 54.72%,respectively,in trifoliate orange grafted plants,while was higher than the value of Pn in citrange grafted plants.In addition,boron deficiency reduced the activity of SOD in trifoliate orange grafted plants,while increased the activity of SOD in citrange grafted plants.3)The content of mineral elements: after boron deficiency treatment,the boron content of each part of‘Newhall' navel orange grafted on trifoliate orange and Carrizo citrange were decreased,but the decreased magnitude of boron content of Carrizo citrange was lower than trifoliate orange.At the same time,the boron deficiency influence the absorption and utilization of zinc.From these physiological indexes and the mineral elements content of each part,comparing to the trifoliate orange,the Carrizo citrange showed a stronger ability to resist zinc deficiency.