Relationships between the Number of First-Flush Flowers and Leaf Water Potential or Leaf ABA Content Affected by Varying Degrees of Water Stress in Meiwa Kumquat (<i>Fortunella crassifolia</i> Swingle)

Altered Carbohydrate Allocation Due to Soil Water Deficit Affects Summertime Flowering in Meiwa Kumquat Trees

“…It was also found that the relationship between the number of first-flush flowers or current leaf water potential and the sugar content of the current stems changed when the sugar content reached approximately 100 mg g −1 DW. Similarly Iwasaki et al [7] reported that severe water stress expressed by a leaf water potential below −1.7 MPa or a leaf ABA content above 5 nmol g −1 did not increase the number of first-flush flowers. Thus, factors related to the level of water stress, such as leaf water potential and sugar content of the plant tissues, appear to have a limited range of influence on the number of first-flush flowers.…”

“…Many previous studies on Meiwa kumquat have shown that the application of a soil water deficit (SWD) for 2-4 weeks during the flower bud differentiation period increases the number of first-flush flowers [4][5][6][7][8][9][10][11]; however, the optimal duration of SWD treatment and its effectiveness varies between years. Iwasaki et al [7] found that severe drought stress that reduced the predawn leaf water potential to below −1.7 MPa or increased the leaf abscisic acid (ABA) content to above 5 nmol g −1 dry weight (DW) did not increase the number of first-flush flowers, suggesting that the leaf water potential needs to be maintained between 0 and −1.7 MPa; however, this condition is difficult to achieve because the leaf water potential fluctuates not only with soil water content but also with the relative humidity of the atmosphere [6,11].…”