Summary
P-protein and the changes it undergoes after wounding of sieve tubes of secondary phloem in one- to two-year old shoots ofHevea brasiliensis has been studied using electron microscopy. The P-protein in the form of tubules with a diameter of 8–9 nm and a lumen of 2–2.5 nm occurred in differentiating sieve elements and appeared as compact bodies which consisted of small aggregates of the tubules. As the sieve elements matured, these P-protein bodies dispersed with a disaggregation of the tubules before they turned into striated fibrils, 10–11 nm in diameter. In wounding experiments, as the mature sieve elements collapsed after cutting, their striated P-protein converted into tubules. These tubules were the same in ultrastructure as the tubules in differentiating sieve elements and they often were arranged in crystalline aggregates.
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Wu, Jl., Hao, Bz. Ultrastructure of P-protein inHevea brasiliensis during sieve-tube development and after wounding. Protoplasma 153, 186–192 (1990). https://doi.org/10.1007/BF01354003
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DOI: https://doi.org/10.1007/BF01354003