Effects of low temperature and gibberellic acid on floral gene expression and floral determinacy in ‘Washington’ navel orange (Citrus sinensis L. Osbeck)

2019 ◽  
Vol 243 ◽  
pp. 92-100 ◽  
Author(s):  
Lisa Tang ◽  
Carol J. Lovatt
HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 516d-516
Author(s):  
Anwar G. Ali ◽  
Carol J. Lovatt

The ability of arginine (50 mM), putrescine (10 and 20 mM), and spermidine (10 and 20 mM) to enhance low temperature stressed-induced flowering of 5-year-old container-grown `Washington' navel orange trees was evaluated. The metabolites were applied to the foliage at the end of the 4-week low-temperature treatment of 8-h days at 10°C and 16-h nights at 7°C; the trees were then moved to warmer conditions. All treatments had a positive effect on floral intensity. Putrescine (20 mM) and spermidine (10 mM) significantly increased (P = 0.05) total flower number and both the number and proportion of leafless inflorescences per tree. However, the number of floral shoots per tree, as well as the number of leafy inflorescences and number of vegetative shoots were not significantly influenced by the metabolites. The results suggest that polyamines are important to the development of flowers, but not leaves, along the axis of the inflorescence.


1989 ◽  
Vol 40 (2) ◽  
pp. 371 ◽  
Author(s):  
H Howie ◽  
J Lloyd

Flowering, fruit set and fruit growth of 'Washington Navel' orange fruit was monitored on 24-year-old Citrus sinensis trees on Sweet orange rootstocks that had been irrigated with either 5 or 20 mol m-3 NaCl for 5 years preceding measurements.Trees irrigated with high salinity water had reduced flowering intensities and lower rates of fruit set. This resulted in final fruit numbers for trees irrigated with 20 mol m-3 being 38% those of trees irrigated with 5 mol m-3 NaCl. Final fruit numbers were quantitatively related to canopy leaf area for both salinity treatments.Despite little difference between trees in terms of leaf area/fruit number ratio, slower rates of fruit growth were initially observed on high salinity trees. This effect was not apparent during the latter stages of fruit development. Consequently, fruit on trees irrigated with 20 mol m-3 NaCl grew to the same size as fruit on trees irrigated with 5 mol m-3 NaCl, but achieved this size at a later date. Measurements of Brix/acid ratios showed that fruit on high salinity trees reached maturity standards 25 days after fruit on low salinity trees.Unimpaired growth of fruit on high salinity trees during summer and autumn occurred, despite appreciable leaf abscission, suggesting that reserve carbohydrate was utilized for growth during this period. Twigs on high salinity trees had much reduced starch content at the time of floral differentiation in winter. Twig starch content and extent of floral differentiation varied in a similar way when examined as a function of leaf abscission. This suggests that reduced flowering and fruit set in salinized citrus trees is due to low levels of reserve starch, most of which has been utilized to support fruit growth in the absence of carbohydrate production during summer and autumn.


1989 ◽  
Vol 40 (2) ◽  
pp. 359 ◽  
Author(s):  
J Lloyd ◽  
H Howie

Effects of irrigation water salinity on tree canopy volume, leaf area, rates of leaf abscission and production, as well as seasonal patterns in leaf osmotic potential (=), starch, soluble sugars and sodium and chloride concentrations were determined for 24-year-old 'Washington Navel' orange trees (Citrus sinensis [L.] Osbeck) on sweet orange (C. sinensis) rootstock. Trees had been irrigated with water containing either 5 or 20 mol NaCl m-3 for 5 years prior to measurements.Trees irrigated with 20 mol NaCl m-3 had a greater number of vegetative flushes in spring. This occurred at the expense of flowering, as numbers of reproductive and mixed flushes were reduced by salinity. Despite a high number of vegetative buds on trees irrigated with 20 mol NaCl m-3, leaf area was still less than low salinity trees.Extensive abscission of spring flush leaves occurred from mid-summer onwards for trees irrigated with 20 mol NaCl m-3. This was not a consequence of leaf water deficit, as more negative leaf osmotic potentials resulting from increased foliar sodium and chloride concentrations resulted in maintenance of leaf turgor. Excessive concentrations of sodium and/or chloride may have been responsible for abscission observed. Some acclimation of foliage to salinity was evident.Irrespective of salinity treatment, leaf osmotic potential became more negative as the season progressed. This was partly due to increased concentrations of soluble sugars in foliage during autumn and winter. Levels of soluble sugars and starch were consistently lower in leaves on trees irrigated with high salinity water, indicating that production rather than utilization of carbohydrate may limit citrus productivity under saline conditions.


Plants ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 95 ◽  
Author(s):  
Li-Ming Wu ◽  
Ce Wang ◽  
Li-Gang He ◽  
Zhi-Jing Wang ◽  
Zhu Tong ◽  
...  

Lanelate navel orange (Citrus sinensis Osbeck) is a late-ripening citrus cultivar increasingly planted in China. The physiological disorder juice sac granulation often occurs in the fruit before harvest, but the physiological and molecular mechanisms underlying this disorder remain elusive. In this study, we found that fruit granulation of the late-ripening navel orange in the Three Gorges area is mainly caused by the low winter temperature in high altitude areas. Besides, dynamic changes of water content in the fruit after freezing were clarified. The granulation of fruit juice sacs resulted in increases in cell wall cellulose and decreases in soluble solid content, and the cells gradually became shrivelled and hollow. Meanwhile, the contents of pectin, cellulose, and lignin in juice sac increased with increasing degrees of fruit granulation. The activities of pectin methylesterase (PME) and the antioxidant enzymes peroxidase (POD), superoxide dismutase, and catalase increased, while those of polygalacturonase (PG) and cellulose (CL) decreased. Furthermore, a total of 903 differentially expressed genes were identified in the granulated fruit as compared with non-disordered fruit using RNA-sequencing, most of which were enriched in nine metabolic pathways, and qRT-PCR results suggested that the juice sac granulation is closely related to cell wall metabolism. In addition, the expression of PME involved in pectin decomposition was up-regulated, while that of PG was down-regulated. Phenylalanine ammonia lyase (PAL), cinnamol dehydrogenase (CAD), and POD related to lignin synthesis were up-regulated, while CL involved in cellulose decomposition was down-regulated. The expression patterns of these genes were in line with those observed in low-temperature treatment as revealed by qRT-PCR, further confirming that low winter temperature is associated with the fruit granulation of late-ripening citrus. Accordingly, low temperature would aggravate the granulation by affecting cell wall metabolism of late-ripening citrus fruit.


1991 ◽  
Vol 116 (2) ◽  
pp. 280-285 ◽  
Author(s):  
Oded Sagee ◽  
Carol J. Lovatt

Maximum leaf NH3-NH4+ content and activity of the de novo arginine biosynthetic pathway occurred during the 1st week after transfer of 5-year-old rooted cuttings of the `Washington' navel orange (Citrus sinensis L. Osbeck) from 8 weeks of low-temperature stress [8-hour days (500 μmol·s-1·m-2) at 15 to 18C/16-hour nights at 10 to 13C]. Both aspects declined in parallel during the subsequent 4 weeks of 12-hour days (500 μmol·s-1·m-2) at 24 C/12-hour nights at 19C, which culminated in maximum bloom. Apical flowers of inflorescences initiated in response to 8 weeks of low-temperature stress exhibited maximum tissue concentrations of NH3-NH4+ and putrescine, and maximum activity of the de novo arginine biosynthetic pathway 1 week after transfer of the trees from the low-temperature induction to the higher temperature (flower buds were 7 × 5 mm, length/width). All three criteria decreased in parallel as flowers developed through Stage V (petal fall). In contrast, spermine concentration increased 7-fold during Stage IV of flower development (flower opening). By Stage V, ovaries contained about equal concentrations of putrescine, spermidine, and spermine. The activity of the de novo tyrosine biosynthetic pathway exhibited a pattern of change independent of flower NH3-NH4+ concentration. Observed changes were not due to increased organ weight or size and persisted when the data were expressed per milligram protein. The results of this study demonstrate that leaves and floral buds undergo parallel changes in N metabolism in response to low-temperature, stress-induced flowering and provide evidence that flower NH3-NH4+ content and putrescine synthesis via argine are metabolically correlated during flower development in C. sinensis.


2011 ◽  
Vol 52 (6) ◽  
pp. 576-580 ◽  
Author(s):  
Yahya Tajvar ◽  
Reza Fotouhi Ghazvini ◽  
Yousef Hamidoghli ◽  
Reza Hassan Sajedi

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