Ecophysiological Response of Lallemantia iberica L. to Exogenous Application of Osmotic Adjustments in Rainfed Production

Lallemantia as an annual plant, with scientific name Lallemantia iberica L. belonged to the Lamiaceae family. The seeds contain oil and mucilage, which are used in the textile and pharmaceutical industries. Lallemantia grows well in arid regions; therefore it can be used as an alternative of the common crops in these areas. The reason for the adaptation to drought is due to the existence of drought-tolerant genes. Crop yield and growth are affected by environmental factors such as water deficit stress due to abnormal processes of physiological processes under stress. Due to the fact that plants synthesize different osmotic compounds under stress conditions, they may respond to their exogenous application against stress conditions. The aim of this study was to evaluate the response of the yield and physiological characteristics of Lallemantia to the application of osmolytes under rainfed and one supplemental irrigation procedure.

This split-plot experiment was conducted at Research Farm of Urmia University (Latitude 45° 10' East, latitude 37° 44' North and altitude 1338 m above sea level) based on a randomized complete block design with three replications during the growing season of 2016-2017. Non-irrigation (rainfed) and one-time irrigation as the main plot, and the foliar application of Osmolytes (proline, glycine betaine, sucrose and distilled water as control) were considered as a sub-plot. The foliar application was performed twice at sunset time. Sampling was done for physiological traits at 80% flowering, and yield was measured at the end of the growing season. The measured traits included leaf Relative Water Content (RWC), chlorophyll index (SPAD), proline, total soluble carbohydrate, glycine betaine, nutrients, plant height, number of capsules per plant, seed number per capsule, 1000-seed weight, biological yield, oil percentage and yield, and mucilage percentage.

The results of analysis of variance showed that the irrigation effect on leaf relative water content, plant height, and oil percentage, and the effect of foliar application of osmolytes on the oil yield were significant at 1% probability level, but 1000-seed weight, seed mucilage percentage, and leaf nitrogen percentage was not affected by irrigation and osmolytes. The interaction between irrigation and osmolytes was significant on the chlorophyll, carotenoid, proline, glycine betaine, total soluble carbohydrates, number of capsules per plant, number of seeds per capsule at 1% probability level, and significant effect on the grain yield, biological yield, phosphorus and potassium at 5% probability level. In both rainfed and supplemental irrigation, the use of proline showed higher chlorophyll index. Proline in both rainfed and supplemental irrigation systems reduced the leaf proline to a minimum concentration. The use of glycine betaine reduced the amount of glycine betaine and total soluble carbohydrates in rainfed and irrigated plants. The highest grain yield (79.56 g.m-2 for rainfed and 85.94 g.m-2 for supplemental irrigation) and biological yield (250.25 g.m-2 for rainfed and 492.65 g.m-2 for supplemental irrigation) belonged to sucrose spraying. Maximum plant height (36 cm) was related to glycine betaine foliar spraying as well as the sucrose application of irrigated plants, while the shortest plant (33 cm) belonged to rainfed plants. Seed weight, as one of the important yield-related factors that currently represents the length and condition of the reproductive period. Though, foliar spray of proline and glycine betaine increased biological yield and grain yield in comparison with control treatment. Leaf potassium decreased in irrigated plants by foliar application of osmolytes, but this is was non-significant in rainfed cultivation. In spite of a little variation of leaf carotenoid in rainfed plants in response to osmolytes, it decreased significantly in supplemental irrigation by proline and glycyline betaine.

According to the results, exogenous application of osmolytes including proline, glycine betaine and sucrose, and or one-time supplemental irrigation, compensated the drought-induced yield loss due to prevent complete discharge of soil moisture. Therefore, the application of foliar spraying and supplemental irrigation is recommended as a viable and cost-effective broad-based solution to increase the yield and yield components of Lallemantia iberica.