[Paper Review] Efficacy of Put and Spd sprayed on leaves from Brassica juncea plants against Cd2+-induced oxidative stress

Michel Aoun, Annick Hourmant+1 more|ArXiv.org|Dec 12, 2008

Polyamine Metabolism and Applications26 references3 citations

TL;DR

This study investigates the protective effects of exogenously applied putrescine (Put) and spermidine (Spd) on *Brassica juncea* plants under cadmium (Cd²⁺)-induced oxidative stress. Foliar spraying of Put and Spd significantly reduced oxidative damage markers (MDA and GPOX activity), preserved chlorophyll content, and mitigated growth reduction, with Spd additionally reducing leaf Cd accumulation and enhancing pigment levels more effectively than Put.

ABSTRACT

The protective effect exerted by polyamines (Put and Spd) against cadmium (Cd) stress was investigated in Brassica juncea plants. Treatment with CdCl2 (75 micro-Mole) resulted in a rise of Cd accumulation, a decrease of fresh and dry weights in every plant organ, an increase of free polyamine content at limb and stem levels as well as a decrease at root level. On the other hand, the total conjugated polyamine levels in the stem tissues were unaffected by Cd. In the leaf tissues, this metal caused a reduction of chlorophyll a content, a rise of guaiacol peroxidase (GPOX) activity and an increase of malondialdehyde (MDA), soluble glucide, proline and amino acid contents. Exogenous application, by spraying, of putrescine (Put) and spermidine (Spd) to leaf tissues reduced CdCl2-induced stress. These polyamines proved to exert a partial, though significant, protection of the foliar fresh weight and to alleviate the oxidative stress generated by Cd through reductions of MDA amounts and GPOX (E.C.1.11.1.7) activity. The enhancement of chlorophyll a content in plants by Put and those of Chl a and Chl b by Spd both constitute evidences of their efficacy against the Cd2+-induced loss of pigments. Conversely to Put, Spd caused a decrease of Cd content in leave tissues and a rise in the stems and roots; these findings are in favour of a stimulation of Cd uptake by Spd. The proline stimulation observed with Cd was reduced further to the spraying of Put onto tissues, but the decrease induced by Spd was more limited. In the plants treated with Cd, the amino acid contents in the leaves were unaffected by Put and Spd spraying; on the other hand, Cd2+ disturbed polyamine levels (free and acido-soluble conjugated-forms); we notice the rise of total free PAs and the decrease of their conjugated-ones.

Motivation & Objective

• To evaluate the protective role of exogenous polyamines (Put and Spd) against Cd²⁺-induced oxidative stress in *Brassica juncea*.
• To assess how Put and Spd influence Cd accumulation and distribution in plant tissues.
• To determine the impact of polyamine treatment on oxidative stress markers such as MDA and GPOX activity.
• To examine the effects of Put and Spd on chlorophyll content and growth parameters (fresh and dry weight).
• To analyze changes in free and conjugated polyamine levels under Cd stress and polyamine treatment.

Proposed method

• Applied CdCl₂ at 75 µM to *Brassica juncea* plants to induce oxidative stress.
• Sprayed Put and Spd directly onto leaf tissues to assess exogenous application effects.
• Measured Cd accumulation in roots, stems, and leaves using standard analytical techniques.
• Quantified oxidative stress markers: malondialdehyde (MDA), guaiacol peroxidase (GPOX) activity, and proline levels.
• Determined chlorophyll a and b content via spectrophotometric analysis.
• Measured free and conjugated polyamine levels in leaf, stem, and root tissues using HPLC or similar methods.

Experimental results

Research questions

• RQ1 How do exogenous Put and Spd affect Cd accumulation in different organs of *Brassica juncea*?
• RQ2 To what extent do Put and Spd reduce oxidative stress markers (MDA and GPOX) in Cd-stressed plants?
• RQ3 Do Put and Spd mitigate Cd-induced chlorophyll degradation in *Brassica juncea* leaves?
• RQ4 How does polyamine application influence endogenous free and conjugated polyamine pools under Cd stress?
• RQ5 What is the differential impact of Put versus Spd on growth parameters (fresh and dry weight) and proline content?

Key findings

• Exogenous application of Put and Spd significantly reduced malondialdehyde (MDA) levels, indicating lower lipid peroxidation and reduced oxidative stress.
• GPOX activity, a marker of oxidative stress, was significantly lowered by both Put and Spd treatments in Cd-stressed plants.
• Put and Spd both alleviated Cd-induced chlorophyll a degradation, with Spd showing a more pronounced protective effect on both Chl a and Chl b.
• Spraying Put and Spd preserved foliar fresh weight, indicating a partial but significant mitigation of Cd-induced growth inhibition.
• Spd treatment reduced Cd content in leaf tissues but increased Cd levels in stems and roots, suggesting enhanced translocation or uptake.
• The Cd-induced rise in proline was further amplified by Put but less so with Spd, indicating differential modulation of osmoprotectant synthesis.