594 Effect of Water Stress during the Harvest Period on the Carbohydrate Reserves of Mature Almond Trees

• Published in: HortScience Vol. 34; no. 3; p. 549
• Main Authors: Esparza, Gaston, DeJong, Ted M, Weinbaum, Steve A
• Format: Journal Article
• Language: English
• Published: 01.06.1999
• ISSN: 0018-5345; 2327-9834
• DOI: 10.21273/HORTSCI.34.3.549C

The effect of water stress during the harvest period on carbohydrate reserves at the end of the growing season was studied for mature, field-grown almond trees. The following irrigation treatments were imposed during 1995, 1996, and 1997: a) full irrigation (FI) (irrigation every 3–7 days), b) moderate stress (MS) (18 days of irrigation cut-off), and c) severe stress (SS) (35, 47, and 53 days of irrigation cut-off for 1995, 1996, and 1997, respectively). Midday stem (Y ms ) and predawn leaf (Y pd ) water potentials were monitored during each season's stress. Three trees of contrasting treatments (FI vs. SS) were excavated on 10 Dec. 1997 and divided into tree components for dry weight and TNC concentration determination. Although there was no significant difference in whole-tree biomass between the excavated FI and SS trees, total new stem growth of SS trees was half of FI trees. TNC concentrations in the organs of SS trees were significantly reduced compared to FI trees. Total calculated whole tree TNC content for SS trees was 26.1% less than FI trees. The difference in TNC content between FI and SS trees was larger for roots (34.9%) than for the aerial parts (21.1%) indicating the higher sensitivity of roots for reflecting reserve status. Although roots constituted just 13.4% of the whole tree biomass, they stored 36.4% of TNC. Only roots exhibited a clear association between the minimum values of Y ms and Y pd during the season and TNC concentration of 12 non-excavated additional trees that were subsampled at the end of the growing season.