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CALCIUM OXALATE CRYSTALS IN THE ROOTS OF MERLOT/KOBER 5BB GRAPEVINES FROM MURFATLAR VINEYARD

Daniela RADUCU

Abstract

The objective of the paper was to investigate the presence of calcium oxalate crystals in the roots of grapevine Merlot/Kober 5BB from Murfatlar Vineyard, and their correlation to the high content of total and active calcium carbonate in soil, inherited from the parent material. Calcium oxalate is a bio-mineralization major product that formed in the superior plants (like the grapevine - Vitis vinifera), occurring as crystals of various shapes (druses, raphides, envelopes, etc.) and supposing to have also various functions. The investigation were conducted in Murfatlar Vineyard, located in Dobrogea Plateau, on the both side of Carasu Valley, where the mean annual temperature is 11.2oC and the mean annual precipitations is 472 mm. The studied soil is Typic Chernozem, formed in loess-like deposits covering Sarmatian limestones. The grapevine roots were sampled (from different depths of the soil, both form healthy plants, and plants affected by iron chlorosis), and impregnated with polyester resins and trapped in the thin sections (20-30 ?m) to be studied by the aim of the microscopic techniques. Despite of the very good ecological characteristics of the Chernozem, the calcium carbonate (inherited from the parent material) which was brought to the/or near the surface (by the specific vineyard technology) in some vineyard areas, increase the susceptibility to iron chlorosis. On the general background of a soil with high pH (7.9 - 8.3) as a result of the presence of CaCO3 in the soil profile, the degree of base saturation is 100%. In these ecological conditions, part of the grapevines was affected by Fe-chlorosis. The micromorphological study showed the presence of calcium oxalate (CaOx) in the cells of the Vitis vinifera roots, both of healthy and affected by chlorosis plants. In accordance with the depth and the health of the vine roots, the CaOx crystals occurred either sporadically and concentrated in the cortex and epidermis tissues (of the healthy plant roots of Vitis), or frequently located in the cortex, epidermis, and xylem rays (of the roots sampled from chlorotic vines). The presence of CaOx crystals in the cells of Vitis vinifera roots may indicate, firstly, their role to increase the mechanical strength of the radicular tissues, enhancing the root penetration power to explore the soil. On the other hand, the accumulation of the calcium oxalate crystals is a response to the high CaCO3 content in the rhizosphere, taking into account the fact that the studied soils from Murfatlar Vineyard had a high content of total and active calcium carbonate. The CaOx presence in root tissues could be also a protection function against phytophagous mesofauna, which are underground root herbivores.

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