Gas exchange, Chlorophyll Fluorescence and Pigments of Noni (Morinda citrifolia L.) under Salt Stress

A M W Cova,Leandra B De Oliveira,André D Azevedo Neto,Rogério F Ribas,Hans R Gheyi,Renata V Menezes

doi:10.5539/jas.v10n2p318

A M W Cova, Leandra B De Oliveira + Show 4 more

Open Access

https://doi.org/10.5539/jas.v10n2p318

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Abstract

Noni is a fruit crop well adapted to different soil and climatic conditions. Aiming to evaluate the physiological responses to salinity, noni seedlings were grown in two levels of NaCl (0 and 100 mM) in nutrient solution and the effects of salt stress on gas exchange, chlorophyll a fluorescence, photosynthetic pigments, relative water content and membrane integrity were assessed after 1, 10, 20, 30 and 40 days of salt stress. The experimental design was a completely randomized in 2 × 5 factorial arrangement with four replications. Salinity did not affect the intrinsic efficiency of water use, but reduced net assimilation of CO2, stomatal conductance, transpiration, carboxylation efficiency and contents of chlorophyll a, b, and total carotenoids. Salinity caused no major changes in chlorophyll fluorescence, however the stressed plants showed a decrease in photoprotection capacity by the cycle of xanthophylls. Salinity did not affect the water status of the leaves, but damages to the integrity of the membranes were observed due to duration of salt exposure. The data indicate that noni presents stomatal closure as a mechanism of salinity tolerance, reducing water loss by transpiration and maintaining the water status.

Highlights

The increase in salinity of the soil solution beyond the tolerance capacity of the plants is an obstacle to agricultural production, particularily in irrigated soils of arid and semi-arid regions
Considering the medicinal importance of noni, its adaptive capacity, and the lack of information on its growth in saline environment, this study aimed to evaluate the gas exchange, the chlorophyll a fluorescene, and the pigment contents in noni plants under stress, for a better understanding of the tolerance mechanisms to salt stress of this species
The shoot dry mass of the noni plants increased during the experimental period (Figure 1)

Summary

Introduction

The increase in salinity of the soil solution beyond the tolerance capacity of the plants is an obstacle to agricultural production, particularily in irrigated soils of arid and semi-arid regions. In Brazil, the semi-arid region occupies an area of 969,589.4 km, located mainly in the Northeast part of the country (Brazil, 2007). In these areas, the scarce availability of water associated with use of brackish groundwater in irrigation, and climatic conditions, decreases the agricultural production, which is one of the main environmental obstacles to agricultural development in the region. Crops in arid and semi-arid regions are often irrigated with poor quality water at certain time of the year, since in most areas it is the only source of water. Plants need to use physiological and biochemical mechanisms to face the jas.ccsenet.org

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