Abstract:

By paraffin method and tissue segregation procedure, the vessel elements and xylem of three citrus seedling rootstocks and their two allotetraploid somatic hybrids were comparatively studied, it showed that: (1) The root xylem and phloem of three citrus seedling rootstocks assumed the concentric circle arrangement, while that of the somatic hybrid rootstocks red tangerine + trifoliate orange, red tangerine + rough lemon arranged unusually, like starfish.（2）Total vessel / xylem area and vessel density were highest for rough lemon, but lowest for trifoliate orange which is less vigorous. (3) Citrus vessel elements all belong to pitted vessel, with perforation plate being simple and always distributed in end wall. The difference of growth potential and nutrient transportability among citrus rootstocks could be reflected by whether the vessel elements have the tail, slope, simple perforation and their proportion in side wall. (4) Rough lemon has good vessel element structure to reflect its strong transportability while that of trifoliate orange is weak. The length and tangential diameter of vessels in citrus somatic hybrid rootstocks are larger than their parents, and have polyploid characteristics; in vessel element character, citrus somatic hybrid rootstocks tend to have more primitive characters which are disadvantageous to transportability.

Key words: Citrus, rootstocks, somatic hybrid, anatomical structure, vessel elements