Comparative anatomical studies of bark and phloem of stout branch and leptos branch in Magnolia biloba

The bark structure of Magnolia biloba, from external to internal parts, includes periderm, cortex, fibre bundies of primary phloem and secondary phloem. Its sieve tube members have P-protein, compound or simple sieve plates, but no starch grains. The pores of these sieve plates are opening, so connecting strand can usually be seen. Companion cells arrange in a row or single cell as long as the sieve tube member. There are about six layer cells in cork of periderm, more oil cells, starch grain cells and sclereid in cortex in stout branches, where as three layer cells, less oil cells, starch grain cells and sclereid in cortex in leptos branches. The width of sieve tube members in stout branches is equal to that in leptos branches, but more length of sieve tube members and more P-protein than that in leptos branches.