Topolin cytokinins enhanced shoot proliferation, reduced hyperhydricity and altered cytokinin metabolism in Pistacia vera L. seedling explants

The effect of 10 mu M meta-topolin (mT) and meta-topolin riboside (mTR) on in vitro proliferation and anomalies of Pistacia vera L. were evaluated and compared to that of 6-benzylaminopurine (BA). The highest proliferation rate (15.6) was recorded in the mT-medium, with a value 6 times higher than in BA-medium. Moreover, the lowest percentage of hyperhydric usable shoots (58,9%) and callus weight (46,9%) were found in mTR-treated shoots. Shoot tip as well as leaf necrosis were not influenced by cytokinin (CK) type. Image analysis was used to evaluate photosynthetic efficiency as well as anthocyanin index. Photosynthesis was more efficient with BA and mTR but the higher anthocyanin accumulation in BA-treated shoots suggests more stress. Endogenous CKs and their metabolites were determined in seedlings and, for the first time, the metabolism of exogenous BA, mT and mTR was studied in pistachio. The stimulating effect on cis-zeatin and its riboside and the appearance of BA and traces of ortho-topolin and para-topolin as natural CKs are discussed. The quantitative and qualitative CK metabolite analyses provides some initial clues as to why topolin would be superior to BA in terms of proliferation rate and avoiding hyperhydricity and allowed a better understanding of the effect of exogenous administration of CK.

Automated summary

The effects of mT and mTR on the proliferation and anomalies of Pistacia vera L. were studied and compared to that of BA. The results showed that mT had the highest proliferation rate and mTR had the lowest percentage of hyperhydric usable shoots and callus weight. However, leaf necrosis and shoot tip were not influenced by the different cytokinins. Image analysis revealed that BA and mTR had higher photosynthetic efficiency, but BA-treated shoots had higher anthocyanin accumulation, suggesting more stress. The study also investigated the metabolism of exogenous BA, mT, and mTR in pistachio.