Boron distribution and mobility in navel orange grafted on citrange and trifoliate orange

Background and Aims

In China, boron (B) deficiency is frequently observed in citrus orchards, and is responsible for considerable loss of productivity and quality. A better understanding of B distribution and remobilization within orange plants is important for developing programs in rational fertilization and effective mitigation of B-deficiency. In the present study (i) the distribution of newly absorbed B and (ii) the translocation of foliar-applied B in ‘Newhall’ navel orange grafted on citrange and trifoliate orange was investigated.

Methods

¹⁰B was applied in the nutrient solution or sprayed on the lower-old leaves of both grafted plants for 35?days.

Results

In the ¹⁰B uptake experiment, citrange-grafted plants showed higher newly acquired total B content and B concentration in both lower-old and upper-old leaves than those in trifoliate-orange-grafted plants. The newly absorbed B in the new leaves was much higher than that in the lower-old leaves and the upper-old leaves in both grafted plants. Foliar application of ¹⁰B to the lower-old leaves resulted in B translocation to the upper-old leaves and the new leaves with preference mainly to the new leaves in both citrange and trifoliate orange when root B supply was relatively low. However, ¹⁰B sprayed to the lower-old leaves not only did not increase the abundance percentage of ¹⁰B in the root, but also reduced B concentration and the total B content in the root.

Conclusions

The results suggest that foliar-applied B can be translocated within both grafted plants, which might also depress B uptake from root medium with low B supply. Rootstock can affect the B distribution in old leaves in navel orange, and newly absorbed B was preferentially transported to the new leaves.