Investigating The Response of Amaranthus caudatus to Short-term Water Deprivation

BACKGROUND AND AIM OF THE STUDY

The agricultural sector is facing enormous challenges to produce 70% more food to cater to the growing population regardless of the detrimental effects of climate change, mainly drought. In plants, water deprivation (WD) induces osmotic stress, leading to the over-accumulation of reactive oxygen species (ROS), which disrupt cellular homeostasis and impede plant growth and productivity. However, plants have evolved complex physiological and biochemical mechanisms to adapt to drought stress. Thus, sustainable agriculture is possible by cultivating climate-smart crops such as Amaranthus as an alternative food source. Amaranthus belongs to the Amaranthaceae family, which comprises over 70 species renowned for their high nutrient and antioxidant content, fast growth, and stress tolerance traits; however, its drought tolerance mechanism is not yet fully understood. Therefore, this study aims at understanding the effect of short-term water deprivation on A. caudatus genotypes including Red Garnet (RG), Love-Lies-Bleeding (LLB), and Ponytail (PT) grown in potting soil under greenhouse conditions.

METHODS

Three A. caudatus genotypes were established for 2 weeks and then subjected to 7 days of water deprivation under controlled greenhouse conditions. The morpho-physiological parameters measured included fresh and dry weight, relative water content (RWC), and shoot length. ROS accumulation was detected using histochemical staining. Biochemical responses, including proline, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and total soluble sugars (TSS), were quantified.

RESULTS AND DISCUSSION

Under water deprivation (WD), the genotypes exhibited distinct morpho-physiological and biochemical responses compared to well-watered (WW) controls. Red Garnet (RG) showed an increase in shoot length from 8.24 cm to 10.67 cm, while Ponytail (PT) displayed a slight increase from 4.55 cm to 4.60 cm, and Love-Lies-Bleeding (LLB) experienced a decrease from 4.69 cm to 4.01 cm. Fresh weight increased across all genotypes under WD, rising from 1575 mg to 1744.45 mg in RG, from 622.22 mg to 1143.33 mg in LLB, and from 510 mg to 933.22 mg in PT. Relative water content (RWC) remained relatively stable in RG and PT but increased in LLB from 47.83 mg to 58.11 mg. Reactive oxygen species (ROS) accumulation was evident under WD, with H₂O₂ quantification showing increases from 0.18 to 0.19 nmol/g FW in RG and from 0.17 to 0.21 nmol/g FW in LLB, while in PT it showed a decrease from 0.17 µmol/g to 0.14 µmol/g. Proline content increased in RG (51.5 to 56.28 µmol/g FW) and PT (30.77 to 43.09 µmol/g FW) but remained largely unchanged in LLB (39.86 to 40.55 µmol/g FW). Malondialdehyde (MDA) increased in PT from 14.01 to 15.83 mmol/g FW, with smaller changes observed in RG and LLB.