Photosynthetic response of two okra cultivars under salt stress and re-watering

Abstract

Two cultivars of okra (Chinese green and Chinese red) were subjected to salt stress (0%, 6%, 12% and 18%) and equal proportions of NaCl and CaCl 2 in Hoagland's nutrient solution and re-watering. Salt stress significantly reduced growth parameters and photosynthetic attributes of both cultivars. Treatment subjected to 18% salt stress caused 90% redundancy in growth parameters of both cultivars compared to control. Re-watering gave a positive response for plant growth of both cultivars in different levels. Chinese green showed better recovery at 6-0% re-watering level and Chinese red showed 12-6% and 6-0%, due to its salt tolerance nature. Considering re-watering water use efficiency and net photosynthetic rate the optimum values of salt tolerance for Chinese green and Chinese red were 8.3% and 12.02%, respectively. The best re-watering degree found as salt stress level ranged from 12.02% to 6% for Chinese red and 8.3% to 2.3% for Chinese green. This study provided a new method for the determination of irrigation time and quantification in crops.ARTICLE HISTORY

Functional traits of okra cultivars (Chinese green and Chinese red) under salt stress

“…2020), due to water scarcity, salinity and loss of fertility. Approximately 33% of the world agricultural land is saline (Azeem et al, 2017b). The impact of salinity has been very high in the northern and coastal parts of China.…”

“…In some cases, the stomata close to maintain the leaf's water status by reducing transpiration. This mechanism leads to reduced CO 2 assimilation rate (Parida and Das, 2004), which affects the photosynthesis process and rate of plant growth (Azeem et al, 2017b). Some plants tolerate salt stress, but a further increase in salt stress exceeding the critical threshold value causes decreases in plant growth and other physiological attributes (Maas and Hoffman, 1977).…”

“…Some papers have evaluated the response of crops and vegetables to different concentrations of saline water and reported a higher production under slight and moderate concentrations of salts (Riccardi et al, 2014;Elshaikh et al, 2018). Furthermore, a number of researchers have reduced the effects of saline irrigation by applying the method of re-watering or by using diluted water after 1 week to a maximum of 3 weeks without considering the duration of the effects on plants (Azeem et al, 2017a(Azeem et al, , 2017bJaved et al, 2017Javed et al, , 2018. However, no reports are related to the plant survival ability or threshold values with respect to salt duration.…”

“…It is classified as a moderately salt-tolerant vegetable crop (Maas and Hoffman, 1977), although it has been found that salt stress reduces okra yield (Shahid et al, 2011). Furthermore, many research works have been conducted on seed germination, as well as the morphological and physiological traits, of different okra cultivars under short durations of salt stress (Azeem et al, 2017a(Azeem et al, , 2017b. However, scarce information is available in literature on how far different physiological attributes in okra are regulated by long durations of salt stress.…”

Effect of salt stress on the growth and photosystem II photochemical characteristics of Lycium ruthenicum Murr. seedlings

“…During their life time, plants may face various abiotic stresses, such as salt excess, drought, and temperature fluctuations, all of which may negatively affect their full growth potential (Forni et al 2017, Yousuf et al 2017, George et al 2018. Salt stress is the most serious abiotic stress that threatens agricultural sustainability by negative impact on plant growth and crop production (Bray et al 2000, Azeem et al 2017, Yousuf et al 2017. The accumulation of salts in soil leads to water stress and nutrient deficiency in plants (Arshi et al 2012).…”