Dynamic state of water characterized by ¹H-NMR relaxation times (T₁) and spectra for pre-chilled tulip plants in growth and developmental stage

The dynamic state of water in cells for pre-chilled tulip 'Gander's Rhapsody' bulbs in growth and developmental stage was studied by ¹H-NMR spectroscopy. Bulbs stored at 15°C for 3 weeks and subsequently at5°C for 9 weeks (pre-chilled), and stored at 20°C for the entire period of 12 weeks (non-chilled), planted and forced at 20°C were used as materials. NMR longitudinal relaxation times (T₁) in scales and nose except for pistil of the pre-chilled bulbs, which flowered at 4 weeks after planting, prolonged and were two times higher than the non-chilled bulbs. There was a positive correlation between the Ti values and water contents in the both bulbs. The shapes of water signals in the nose showed sharp peak in flower stalk internode and several peaks in petal and stamen except for pistil with different chemical shifts. Thus, it suggests that there were several compartments where water molecules interacted with the local environment. Starch granules were disappeared in the scale and small starch granules were observed in the nose of the pre-chilled bulb. On the contrary, in the scales of the non-chilled bulbs, the conversion of starch to mobile sugars slightly occurred until the same period, and the growth was severely inhibited. Therefore, marked prolongation of T₁, appearance of spectra peaks in NMR signal, increase of water content in the pre-chilled bulbs after planting indicated that active metabolism has already prepared by onset of the starch degradation during the pre-chilling treatment. Thereafter, remarkable increase of free water in the scales and nose of the bulbs, and sugar transport to the nose may enhance rapid growth and normal flowering of tulip plants.