Relationships between Root Size and Postharvest Respiration Rate

Abstract

Sugarbeet (Beta vulgaris L.) root size has been implicated as a factor influencing storage respiration rate, yet the relationship between root size and respiration is unclear. Sugarbeet root size is dependent on cultural, environmental, and genetic factors and can vary significantly within and between fields. To evaluate the effect of root size on respiration rate and explore the morphological mechanisms that regulate respiration in sugarbeet roots, the relationships of respiration rate and total root respiration with root mass, surface area, and the ratio of surface area to mass (specific surface area) were determined using three field-grown varieties. Respiration rates for the sugarbeet varieties KW 2249, VDH 46177, and Beta 4818 were associated with root mass (R 2 = 0.55, 0.40, and 0.47), surface area (R 2 = 0.38, 0.29, and 0.39), and specific surface area (R 2 = 0.57, 0.34, and 0.36) by sigmoidal relationships. For each variety, there was a critical root size above which size had little impact on respiration rate. Below this critical size, root respiration rate increased substantially as root mass or surface area decreased. This critical beet size was 0.68, 0.50, and 0.86 kg for KW 2249, VDH 46177, and Beta 4818, respectively. Total respiration, i.e. respiration per root, for KW 2249, VDH 46177, and Beta 4818 was directly associated with root mass (R 2 = 0.71, 0.52, and 0.21) and surface area (R 2 = 0.72, 0.46, and 0.11) and