Objectives This paper showed the study of the difference in photosynthetic characteristics between citrange boron (B)-insensitivity and trifoliate orange (B-sensitivity) seedlings.
Methods Hydroponic experiments were conducted with 5 B levels, including 0 (B0)、2 (B2)、5 (B5)、10 (B10) and 50 μmol/L (B50) . The difference of B-efficiency and photosynthesis between the two rootstocks was analyzed according to the concentration of B forms, photosynthetic pigment, net photosynthetic rate and carbohydrate.
Results The B effective utilization rate of citrange sample was higher than trifoliate orange sample under the same treatment, especially in the treatment of B0. The citrange used 38.6% more B compared with trifoliate orange. Under the different B treatments, R value (R=semi-bound B/free B) was much lower in trifoliate orange samples than citrange samples, which indicated B utilization of citrange at the cellular level was significantly higher than trifoliate orange. B deficiency reduced photosynthetic pigment content (Chl a, Chl b, Car) of two rootstocks leaves, and there were much more significant effects of B deficiency on trifoliate orange. B deficiency significantly reduced the net photosynthetic rate in both two rootstocks. The net photosynthetic rate was significantly higher in citrange than trifoliate under the condition of B-deficiency (B0, B2, B5) and rich B (B50). There was a higher content of soluble sugars, fructose, and starch in B0 treated samples compared with other treatments. Under B-deficiency treatment, moreover, a higher level of soluble sugars, sucrose, and fructose was observed in trifoliate orange than that in citrange.
Conclusions Citrange showed more effective B utilization than trifoliate orange. The differences of photosynthetic characteristics and accumulation of photosynthetic products could be one of the key factors leading to the different B-efficiency of two rootstocks.
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