Determining Salinity Threshold Level for Castor Bean Emergence and Stand Establishment

Abstract

Castor bean (Ricinus communis L.) is grown on marginal lands that can be prone to having medium to high salt concentrations. This study was done to identify a salinity threshold level for castor bean emergence and stand establishment. Seedlings were first cultured in organic matter–soil mixed media at different salinity levels (0.5, 3.6, 7.1, 10.4, and 13.6 dS m−1) and then transplanted into pots filled with soils at similar salinity levels (0.4, 3.6, 7.1, 10.4, and 13.6 dS m−1). Emergence, survival, seedling growth, nutrient accumulation, and leaf photosynthetic parameters were determined. The salinity threshold level was identified at 7.1 dS m−1 At this salinity level or lower, the emergence rate and survival rate reached 75% or higher; and seedling growth, nutrient accumulation, and leaf photosynthetic parameters were not severely affected. As the salinity level increased to 10.4 and 13.6 dS m−1, emergence rate dropped to below 70%, and survival rate below 50%. Photosynthetic rate and stomatal conductance were reduced by up to 66% and chlorophyll reading by up to 24%. Nutrient uptake and accumulation were also significantly reduced at these two salinity levels. Our results indicate that castor bean could be cultured in plastic seedling trays filled with organic matter–soil mixed seedling media and then transplanted into conventional soils provided that the salinity levels in seedling media and conventional soils are ≤7.1 dS m−1

Gibberellic Acid and Salinity Affected Growth and Antioxidant Enzyme Activities in Castor Bean Plants at Early Growth Stage

“…All the growth parameters including plant height, stem diameter, the weight of root, stem, leaf, and the whole plant and some physiological parameters including the activity of SOD and POD were even increased at the 50 mM salinity level as compared with the non‐salinity level, indicating that castor plants were not negatively affected at a low salinity level. This finding was partially in agreement with our previous study in which the salinity level of 3.6 dS m −1 significantly increased taproot length, average root length, the weight of root, stem, and the whole plant (Zhou et al, 2010). But different results were reported by Janmohammadi et al (2012), who found that 50 mM NaCl resulted in a significant decrease in the root weight and leaf of castor bean seedlings.…”

“…Castor plant, as a salt‐tolerant crop, grows well in semiarid and arid regions, areas that often have low‐to‐medium saline concentrations (Jeschke and Pate, 1991, 1992). Its plantation has attracted the attention from both agronomists and producers (Zhou et al, 2010).…”

“…It can grow well in semiarid and arid regions, areas that often have low to medium saline concentrations (Jeschke and Pate, 1991, 1992). Although castor bean plant is medium salt tolerant, the early growth of seedlings is severely inhibited when the salt concentration in growing media was higher than certain levels (Zhou et al, 2010; Janmohammadi et al, 2012). Early seedling growth is crucial for plant establishment and final yield of the crops.…”

Exogenous Hormones Alleviated Salinity and Temperature Stresses on Germination and Early Seedling Growth of Sweet Sorghum

“…The quality of seed germination is usually expressed with parameters such as germination percentage, germination velocity, and germination vigor index. The vigorous growth of seedlings, often expressed with root and shoot growth, usually lays a solid foundation for an optimum plant population, especially under saline soil conditions (Zhou et al, 2010).…”

<b>Optimizing row spacing and plant population arrangement for a new short-height castor genotype in fall-winter

“…The castor plant is tolerant to drought and adapted to many cropping conditions (BABITA et al, 2010;CARVALHO et al, 2010;ZHOU et al, 2010). In Brazil, new castor genotypes have been developed with a high yield potential, a short growing cycle, even maturation, indehiscent fruit, and a short stature and are suitable for mechanical harvesting techniques.…”