How does the flooding stress occurring in different harvest times affect the morpho-physiological and biochemical characteristics of spinach?

Recently, flooding stress caused by nonuniform and excessive rainfall, which occurs in most regions of the world due to global climate change, has adversely affected plant growth and development. In many regions, spinach (Spinacia oleracea L.) is severely affected by flooding stress during the cultivation period. This study aimed to determine the effects of flooding stress on the morpho-physiological and biochemical properties of spinach in different harvest times. The changes in the morpho-physiological and biochemical parameters of spinach were determined at two levels of stress, including no stress and flooding stress, as well as five different harvesting times. The results demonstrate that while flooding stress reduced some growth parameters such as chlorophyll a, b and protein content, it caused statistically significant increases in proline, hydrogen peroxide (HO), malon-dialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activity. Principal Component Analysis (PCA) showed that first and second components explained 71.59 % and 73.50 % of variation under no stress and flooding stress conditions, respectively. Correlation and PCA analysis revealed that relative leaf water content (LWC), membrane damage, and chlorophyll a and b are important parameters as they are affected in response to flooding stress. Thus, the flooding stress occurring at harvest times negatively affected the growth and development of spinach and caused significant changes in the morpho-physiological and biochemical properties.