Characterisation of three ACC synthase gene family members during post-harvest-induced senescence in broccoli (Brassica oleracea L. var. italica)

We investigated the gene expression profiles of different members of the 1-aminocyclopropane-1-carboxilic acid (ACC) synthase (EC 4.4.1.14) gene family in broccoli (Brassica oleracea L. var. italica) during the post-harvest-induced senescence process. Using RT-PCR, three different cDNAs coding for ACC synthase (BROCACS1, BROCACS2 and BROCACS3) were amplified from floret tissue at the start of the senescence process. The three genes share relatively little homology, but have highly homologous sequences in Arabidopsis thaliana, and could be functionally related to these counterparts. Southern analyses suggest that BROCACS1 and BROCACS3 are present as single copy genes, while there are probably two copies of BROCACS2. All three genes showed different expression patterns: BROCACS1 is likely to be either wound - or mechanical stress-induced showing high transcript levels after harvesting, but no detectable expression afterwards. BROCACS2 shows steady expression throughout senescence, increasing at the latest stages, and BROCACS3 is almost undetectable until the final stages. Our results suggest that BROCACS1 could be required to initiate the senescence process, while BROCACS2 would be the main ACC synthase gene involved throughout the post-harvest-induced senescence. BROCACS3's expression pattern indicates that it is not directly involved in the initial stages of senescence, but in the final remobilization of cellular resources.

Characteristics of banana fruit from nearby organic versus conventional plantations: A case study

This case study reports the post-harvest qualities of conventionally versus organically grown banana fruit from nearby plantations in the Dominican Republic. The comparison involved six repeated harvests over the transition from cooler to hotter seasons. Green mature Cavendish 'Grande Naine' banana fruit were shipped to the UK. They were triggered to ripen with ethylene gas and kept under simulated retail conditions. Fruit mass, colour, firmness and flavour parameters were measured every second day over 12 d of shelf life. Sensory comparisons were conducted on four of the six harvest times. Significant differences (P<0.05) in measured quality attributes between conventionally and organically grown fruit were few and marginal. Moreover, any differences were inconsistent across harvest-times and during shelf life. Thus, organically and conventionally grown product had almost identical qualities. Sensory comparison confirmed that there was no flavour difference. This case study provides data that challenge a general perception that organic bananas have better flavour than conventional bananas.

Effect of seasonal variation and storage temperature on leaf chlorophyll fluorescence and vase life of cut roses

Low temperature injury (LTI) of roses (Rosa hybrida L.) is difficult to assess by visual observation. Relative chlorophyll fluorescence (CF; F-v/F-m) is a non-invasive technique that provides an index of stress effects on photosystem 11 (PS 11) activity. This instrumental technique allows determination of the photosynthetic efficiency of plant tissues containing chloroplasts, such as rose leaves. In the present study, pre- and Post-Storage measurements of F-v/F-m were carried out to assess LTI in 'First Red' and 'Akito' roses harvested year round. Relationships between the pre-harvest environment conditions of temperature, relative humidity and photon flux density (PFD), F-v/F-m, and, vase life duration after storage are reported. After harvest, roses were stored at 1, 5 and 10 degrees C for 10 days. Non-stored roses were the control treatment. F-v/F-m ratios were reduced following storage, suggesting LTI of roses. However, reductions in F-v/F-m were not closely correlated with reduced vase life duration and were seasonally dependent. Only during winter experiments was F-v/F-m of roses stored at 1 degrees C significantly (P <= 0.001) lower compared to F-v/F-m of non-stored control roses and roses stored at 5 and 10 degrees C. Thus, the fall of F-v/F-m was due to an interaction of growing season and storage at 1 degrees C. Vase lives of roses grown during winter were significantly (P <= 0.001) shorter compared to roses grown during summer. Length of vase life was intermediate for roses grown during autumn and spring. Because of the lack of correlation between F-v/F-m and post-storage vase life it is concluded that the CF parameter F-v/F-m is nota practical index for assessing LTI in cold-stored roses. Higher PFD and temperature in summer were positively and significantly correlated with maintenance of post-storage FvIF ratios and longer vase life. It is suggested that shorter vase lives and lower post-storage F-v/F-m values after storage at 1 degrees C are consequences of reduced photosynthesis and smaller carbohydrate pools in winter-harvested roses. (c) 2004 Elsevier B.V All rights reserved.