Selected physiological responses of roselle (Hibiscus sabdariffa) to drought stress

Abstract

This greenhouse study was carried out to determine the impact of drought on plant growth, photosynthetic rate and the recovery of photosynthesis after drought relief. Twenty four Roselle plants were equally divided between the control and the treatment groups, which received 100% and 25% soil saturation respectively. The plants were grown under greenhouse conditions with the temperature averaging 27 ± 2ºC. The treatments were applied with seven cycles of watering until the plants reached the anthesis stage. The drought influence caused a significant reduction in the plant height, flower number, and photosynthetic rate. Re-watering the plants growing under drought to 100% water saturation resulted in complete recovery of photosynthetic rate within forty-eight hours. However, rewatering to 25% showed only 30% recovery in photosynthetic rate after forty-eight hours. Photosynthetic pigments including chlorophyll a, b and carotenoid were not significantly influenced by the drought. Similarly, total phenolic compound concentration of the calyx was insignificant between the treatments. However, Anthocyanin concentration of the calyx was significantly higher under the drought treatment.

Influence of Glycinebetaine on Water Stress Tolerance of Hibiscus sabdariffa L. Plant

“…1) Moreover, the interaction between irrigation treatments and glycinebetaine showed that the highest values for chlorophyll a and b were recorded from plants irrigated at 65% of ASMD combined with GB at 25 mM in both growing seasons. These findings are supported by the previous investigation on roselle (Evans and Al-hamdani, 2015) who stated that chlorophyll a and b were not significantly affected by the drought. Also, these results were not consistent with the results from Roussos et al, (2010) who stated that drought significantly enhanced chlorophyll a and chlorophyll b concentration of olive trees compared to irrigated trees.…”

“…The highest seeds dry weight (g/plant) and calyces dry yield (kg/fed) were obtained from plants irrigated at 65 % of ASMD in the two growing seasons. The observed decline in plant growth and yield under water stress treatments is deemed a common response for water shortage conditions, which were earlier reported for roselle by Evans and Al-Hamdani, (2015) and Sakimin et al, (2017) and on many plants, e.g., Phaseolus vulgaris, Carica papaya and Pisum sativum (Xing and Rajashekar, 1999Mahouachi et al, 2012and Osman, 2015. However, exogenously applied GB showed a positive impact on improving roselle plants growth and yield under water stress treatments.…”

“…Drought stress has unfavorable influences on different plant species , e.g., water deprivation reduced shoot biomass, number of pods/plant and pod dry weight of bean plants (Xing and Rajashekar, 1999), achene yield/plant of sunflower (Iqbal et al, 2008) photosynthetic rate and leaf fresh weight of papaya seedlings (Mahouachi et al, 2012) and diminished growth and yield of peas (Osman, 2015) as well as basil plants (Mahmoud et al, 2017). In addition to, decreasing height and flower number while increased anthocyanin concentration of roselle plants (Evans and Al-hamdani, 2015).…”

“…Although, some of the literature are available about water stress impacts on roselle (Evans andAl-hamdani, 2015 andSakimin et al, 2017) information concerning the influence of exogenous glycinebetaine on physiological characteristics of roselle under water deficit environment is lacking. Therefore, we hypothesized that foliar application of GB could effectively minimize drought-induced harmful effects on roselle growth and yield.…”

Anthocyanin Induction by Drought Stress in the Calyx of Roselle Cultivars

“…The production of phytochemicals in fruits varies with the stage of development, stress level, defense mechanisms of the plant, genotype, and genotype*environment interactions [10,11]. It has been reported that water stress induces oxidative stress as a result of the formation of free radicals; to counteract the damage, the plant generates a signaling cascade, activating defense mechanisms that favor the production of secondary metabolites [12][13][14][15].…”