Dimming Effects on Biomass and Structure

Changes in structure and biomass of seedling fava beans were assessed with simulated dimming and UV-B exclusion in Hawaii. For total height, internode lengths, specific leaf weight and total, leaf, stem and branch biomass, no statistically significant differences were found between plants grown in full sun and under the dimming treatment, either with or without UV-B exclusion (Table 13.1; Fig. 13.6, upper, middle). Non-significant decreasing trends (p > 0.05) from full sun to reduced sun with UV-B exclusion were found for biomass and for many internode heights. One exception to this was a non-significant increase along the same radiation gradient for branch biomass. Evidence that more branching may have been induced with UV-B exclusion were obtained by assessing the number of plants with 8 -10 internodes and the number of leaf and branch internodes. More plants grown under the dimming treatment with UV-B excluded had 8 -10 internodes (Fig. 13.6, lower), and more branches per plant and greater branch biomass were measured (although not significant) for this treatment (Fig. 13.7).

Figure 13.6 Total plant height (upper), height of intemodes 1 - 6 (middle) and portion of experimental plants with internodes 8 - 10 (lower) for fava beans grown under simulated global dimming and UV-B exclusion at the Mauna Kea, Hawaii field site. Error bars represent 1 standard error. Values with same letter designation are not significantly different (p > 0.05). No significant differences were found among internode heights (middle panel). Dosimetry and meteorological data as in Fig. 13.3

Figure 13.6 Total plant height (upper), height of intemodes 1 - 6 (middle) and portion of experimental plants with internodes 8 - 10 (lower) for fava beans grown under simulated global dimming and UV-B exclusion at the Mauna Kea, Hawaii field site. Error bars represent 1 standard error. Values with same letter designation are not significantly different (p > 0.05). No significant differences were found among internode heights (middle panel). Dosimetry and meteorological data as in Fig. 13.3

Figure 13.7 Average total number of internodes, number of branches and number of leaf insertions (upper) and weight of leaves, stems and branches (lower) for fava bean plants grown under simulated global dimming and UV-B exclusion at the Mauna Kea, Hawaii field site. Error bars represent 1 standard error. No significant differences (p > 0.05) were found among treatments for the number of internodes and weights of plant parts. Dosimetry and meteorological data as in Fig. 13.3

Figure 13.7 Average total number of internodes, number of branches and number of leaf insertions (upper) and weight of leaves, stems and branches (lower) for fava bean plants grown under simulated global dimming and UV-B exclusion at the Mauna Kea, Hawaii field site. Error bars represent 1 standard error. No significant differences (p > 0.05) were found among treatments for the number of internodes and weights of plant parts. Dosimetry and meteorological data as in Fig. 13.3

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