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Influence of UV-B radiation and soil moisture stress on broccoli (Brassica oleraceae) seedings Mohan, Mercy


The interaction between ultraviolet-B (UV-B; 280-320 run) radiation and soil moisture stress (SMS) on the growth of broccoli (Brassica oleracea L. var. italica cv. Purple Sprouting) seedlings was studied. The seedlings were grown under different levels of UV-B radiation and SMS and their combinations in the greenhouse. The factorial experiment consisted of sixteen treatments: four levels of SMS [normal {100% field capacity (FC)}, mild (80% FC), moderate (60% FC) and severe (40% FC)] x four levels of UV-B radiation [no UV-B (0), ambient (4 kJ m⁻² d⁻¹), and two above ambient levels (7 and 11 kJ m⁻² d⁻¹)]. The study showed that the responses of broccoli seedlings grown under the combination of stresses were significantly different from those grown under individual stresses. The combination of stresses significantly increased the synthesis of epicuticular wax and UV-B absorbing compounds in the leaves and reduced leaf area compared to individual stresses. Seedlings grown under the combination of UV-B radiation and SMS had higher water potentials than the moisture stressed seedlings grown without UV-B radiation. Growth indices such as specific leaf weight (SLW), leaf area ratio (LAR), leaf weight ratio (LWR) and shoot:root ratio (SRR) indicated that the morphology and biomass allocation were strongly influenced by the interaction. UV-B irradiance with soil moisture stress also caused a reduction in growth parameters like plant height, fresh biomass and dry biomass compared to individual stresses. The results of this study suggest that UV-B radiation can minimize or mask the adverse effect of SMS on broccoli seedlings.

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