Analytical Sciences

Abstract − Analytical Sciences, 22(8), 1125 (2006).

Borate Cross-Linked/Total Rhamnogalacturonan II Ratio in Cell Walls for the Biochemical Diagnosis of Boron Deficiency in Hydroponically Grown Pumpkin
Toshiro MATSUNAGA* and Tadashi ISHII**
*National Agricultural Research Center, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8666, Japan
**Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan
Boron (B) is an essential micronutrient for vascular plants. The function of B has been demonstrated to cross-link monomeric rhamnogalacturonan II (mRG-II) to form dimeric RG-II-borate (dRG-II-B), and thus to stabilize plant cell walls. The dRG-II-B to total RG-II ratio in the cell walls of pumpkin hydroponically grown under various low-B conditions was analyzed to evaluate its applicability to the diagnosis of plant B deficiency. The dRG-II-B ratio in cell walls ranged between ∼0.9 in B-sufficient tissues and ∼0.15 in severe B-deficient tissues, reflecting the B nutritional status of tissues. This result indicates that the degree of B shortage in plant tissues is very likely to be diagnosed by the dRG-II-B ratio in cell walls.