Carbon balance of <i>Yucca elata</i> Engelm. during a hot and cool period in situ

TitleCarbon balance of Yucca elata Engelm. during a hot and cool period in situ
Publication TypeJournal Article
Year of Publication1983
AuthorsSisson W.B.
Date Published1983

Respiratory activity of intact, attached roots was measured under field and controlled conditions. Root respiration of Yucca elata Engelm. was highly temperature dependent: Q10 values decreased from 2.1 (12-22° C) to 1.7 (26-36° C) as temperatures increased. Respiration ceased after 5 h at 42° C. In the field, in August, when net leaf photosynthesis was severely depressed, the die! fluctuation in the respiration rate of suberized and partially suberized roots was predominantly a function of temperature. A photoperiod-associated rise in respiration rates apart from temperature response occurred in February for nonsuberized, partially suberized, and suberized roots when active net photosynthesis occurred throughout the photoperiod. In whole-plant root systems, respiratory C02 was 3.2 and 4.3 mg C02. g Dw -1. d -1 in August and February, respectively, when adjusted for the proportion of suberized and nonsuberized lateral roots. On a whole-plant basis, 0.89 mg C · g DW -1 · d -1 was gained during February and 0.46 mg C · g DW -1 · d -1 was lost in August. The belowground: above ground ratio of whole-plants in situ was 0.42 on a shallow soil where vertical root growth was limited to a soil depth of 68 cm and ranged from 1.29 to 5.94 (.X= 3.31) in deep sands. No leaf dark fixation of C02 was observed in field plants during August and February, nor in well-watered plants or plants subjected to drought in laboratory studies. Although small die! fluctuations in leaf acidity occurred in both field and greenhouse-grown plants, results of this study suggest that Y. elata is a C3 plant.