Physiological and anatomical mechanisms induced by water deficit on the longevity and post-harvest quality of amaryllis stems

Abstract

Insufficient information on the water requirements of amaryllis makes the production of this crop difficult in regions with a semi-arid climate. Furthermore, increase in water deficit promotes anatomical and physiological changes, which alter the quality of the stems and their vessel life. The morphophysiological, anatomical and quality changes of amaryllis stems subjected to different irrigation depths {20, 40, 60, 80 and 100 % of the reference evapotranspiration (ETo)} were evaluated. Furthermore, evapotranspiration (ETc) and crop coefficients (Kc) were established and five phenophases (φPh) were delineated based on floral stem growth rate (∂TCF/ ∂t). Irrigation with 80 % ETo provided a higher leaf area index, photosynthetically active radiation intercepted and ∂TCF/ ∂t. Kc and ETc values decreased throughout the cycle {0.84 and 4.9 mm day−1 (φPhI) to 0.30 and 0.6 mm day−1 (φPhV)}. Irrigation with 20 % ETo reduced the PSII quantum yield (Fv/Fm), the electron transport rate (ETR) and the content of photosynthetic pigments. In addition, ETo increased non-photochemical quenching (NPQ), oxidative damage (TBARs and H2O2), enzymatic (CAT, SOD and APX) and non-enzymatic (CFT, AA, FRAP and DPPH) antioxidant activity. Irrigation with 20 and 40 % of ETo provided greater stomatal density, thickness of the palisade and lacunous parenchyma, stem cells with smaller size and thicker epidermis and collenchyma. Surprisingly, the reduction in water availability (20 and 40 % of ETo) increased tolerance to post-harvest stress, increasing longevity, and concentration of secondary metabolites in the petals, but reduced the size of the stems. The water deficit negatively impacted the growth of amaryllis stems, increased damage and oxidative protection, resulting in stems with a longer vase life, however, with a low market price. Irrigation with 80 % ETo enabled the production of floral stems with commercial standards for cutting and potting.