No abstract

Selenium‐biofortified broccoli (Brassica oleracea L. var. italica Plenck) is an important source of micronutrients in a healthy human diet. Therefore, studies are needed on the commercial production of selenium‐enriched broccoli. We analyzed the effect of the foliar application of sodium selenate and sodium selenite in doses of 50 and 100 g ha−1 on the growth, photosynthetic parameters, selenium accumulation, and commercial quality of broccoli in two cultivars (‘Belstar’ and ‘Legend’) used for fresh crops market grown under field conditions. The application of both doses of selenate and the highest dose of selenite induced a significant increase in the head fresh weight (FW) only in cultivar Belstar. However, the dry matter content of the heads was not significantly affected by selenium or the cultivar of broccoli. In addition, the increase in the water use efficiency, mainly due to the reduction of the transpiration rate, could explain the significant increase in the head FW without modifying the head dry matter content in Belstar. On the other hand, selenium treatments before harvest maintained the green color and did not affect the firmness and diameter of the heads at harvest. The selenium content of the heads increased markedly in a dose‐dependent manner in both cultivars, with both selenium treatments. The results of this study indicate that the response to selenium treatments differs between broccoli cultivars and that the use of both selenium salts in foliar form would be a good strategy to obtain selenium‐enriched broccoli, without affecting the commercial quality of the heads.

The objective of this work was to compare the effect of different priming osmotic agents and durations on melon germination in: 1) low temperature stress; 2) saline stress; and 3) low temperature and saline stress. The osmotic agents were polyethylene glycol 6000, KNO3+K3PO4, CaCl2 and NaCl, with -1.5 MPa osmotic potential. Priming durations were 3 and 6 days (d). Germination percentage (GP) and mean germination time (MGT) were measured. At 12°C the best GP was 14% with CaCl2/3-d, without germination in control. At 25°C the best GP was 100% with CaCl2/3-d. MGT was reduced one day. At -0.7 MPa GP was 100% with CaCl2/3-d and NaCl 3d. At -1.0 MPa the best GP were 46 and 50% for 3d with NaCl and CaCl2respectively without germination in control treatment. At 12°C and -1.0 MPa the best GP were CaCl2/3-d and CaCl2/3-d (14 and 10% respectively). It is concluded that at 12°C, the increase in GP would not justify the use of priming. At 25°C priming increased GP and reduced MGT. At -0.7 MPa priming increased germination, while at -1.0 MPa the increase is not agronomical considerable. At 12°C and -1.0 MPa the increase of germination is not agronomical important.

Growth of 'Fiesta Gitana' calendula (Calendula officinalis) in growth medium prepared from 75% (vol.) composted willow (Salix sp.) sawdust (WS), with or without additional nitrogen (N) (4% w/w) during composting, and 25% (vol.) perlite was examined. Total plant dry matter, dry matter partition to flowers, and plant height at 77 days after planting were similar in media containing composted WS to values in achieved in a sphagnum peat:perlite (75:25, vol.) control medium. Relative to these media, non-composted WS:perlite (75:25, vol.) resulted in average reductions of total dry matter (57%), dry matter partition to flowers (50%), plant height (43%), flower diameter (73%), and flower buds per plant (82%). In a further study, increasing the proportion of N-enriched composted WS in perlite from 25% to 75% did not affect total dry matter, plant height, or flower number per plant of 'Fiesta Gitana' calendula or 'Perfection Gold' marigold (Tagetes erecta) compared to values achieved in the sphagnum peat:perlite (75:25, vol.) control medium. Since flower diameter decreased in both species when the N-enriched composted WS exceeded 50%, we suggest that this "waste" product can substitute for all the sphagnum peat, but should not exceed 50% volume in a perlite mixture.

Ethylene is considered one of the most important plant hormones orchestrating plant responses to flooding stress. However, ethylene may induce deleterious effects on plants, especially when produced at high rates in response to stress. In this paper, we explored the effect of attenuated ethylene sensitivity in the Never ripe (Nr) mutant on leaf photosynthetic capacity of flooded tomato plants. We found out that reduced ethylene perception in Nr plants was associated with a more efficient photochemical and non‐photochemical radiative energy dissipation capability in response to flooding. The data correlated with the retention of chlorophyll and carotenoids content in flooded Nr leaves. Moreover, leaf area and specific leaf area were higher in Nr, indicating that ethylene would exert a negative role in leaf growth and expansion under flooded conditions. Although stomatal conductance was hampered in flooded Nr plants, carboxylation activity was not affected by flooding in the mutant, suggesting that ethylene is responsible for inducing non‐stomatal limitations to photosynthetic CO2 uptake. Upregulation of several cysteine protease genes and high protease activity led to Rubisco protein loss in response to ethylene under flooding. Reduction of Rubisco content would, at least in part, account for the reduction of its carboxylation efficiency in response to ethylene in flooded plants. Therefore, besides its role as a trigger of many adaptive responses, perception of ethylene entails limitations in light and dark photosynthetic reactions by speeding up the senescence process that leads to a progressive disassembly of the photosynthetic machinery in leaves of flooded tomato plants.