Abstract
Hydraulic properties related to growth of flower stalks, leaves and roots in tulip (Tulipa gesneriana L.) plants were studied after bulbs were stored at 20°C continuously or under low temperature for 4-, 7- or 9-week periods. The shorter cold storage periods in the bulbs resulted in the reduced growth of roots, leaves and flower stalks. Differentiation and development of vascular bundles in flower stalks of growth-reduced plants caused by the shorter cold storage periods were similar to those of rapidly growing tulip plants. A decrease in hydraulic conductance was associated solely with reduced cell elongation rates, but not with the processes of cell division and tissue differentiation. Sizes of the water potential gradient between the water source and the expanding cells were linearly related to speeds of growth rates in all organs. Further, the shortage of cold periods led to lower hydraulic conductance in the zone of elongation of those tissues. Therefore, reduced growth in the elongating zone of all tulip tissues was associated with the reduction of both the hydraulic conductance and the size of the growth-induced water potential regardless of the period of low temperature treatments.
