“Halophytic Grasses of Pakistan: Physio-biochemical adaptive components of salinity tolerance

Physio-biochemical processes involved in stress tolerance of some potential desert grasses

Low availability of water due to either low rainfall or irrigation water has resulted into deserts in most regions of the world. Most of the deserts are naturally prone to multiple stresses primarily including drought, salinity, temperature extremes, nutrient deficiency, etc. In Pakistan, there are four major deserts, of which Cholistan desert experiences a myriad of environmental stresses causing different types of ecological niches. These specific types of ecological habitats, some rich in high levels of soluble salts, are colonized mainly with a variety of salt tolerant plants. Of them, grasses are of profound importance as they provide fodder to animals being rared within the desert. Moreover, these grasses being tolerant to drought and high temperature, are also highly tolerant to salinity as this menace occurs in patches in between the sand dunes. Salt tolerant grasses have been categorized into different categories from obligate halophytes through less salt tolerant. It is believed that highly salt tolerant grasses have been growing in their native habitats since a long span of time, so they must have evolved with time some prominent adaptive characteristics to tolerate to salinity stress. Most distinctive physio-biochemical and molecular adaptative features in the salt tolerant grasses were recorded to be inclusion of salts, sequestration of salts from the cytosol to the vacuole, retention of salts in roots thereby allowing low quantity of toxic salts to the upper plant parts, excretion of salts from leaf surface, maintenance of high tissue K/Na ratios, and enhanced manifestation of osmoregulation and oxidative defense system. However, the extent of expression of all these physio-molecular traits were found to be positively related with degree of salt tolerance of different grasses. Although considerable efforts are being made to comprehensively characterize and elucidate the mechanisms of salt tolerance in commercial crops using the advanced omics tools such as genomics, transcriptomics, proteomics, metabolomics, ionomics, etc., relatively little work has been done to fully uncover all such mechanisms in these grasses through the advanced technologies. Thus, future research needs to be focused on this issue, because some of these highly salt tolerant grasses are a good source of salt tolerance genes, that can be utilized to improve salinity tolerance of commercial crops.

Low availability of water due to either low rainfall or irrigation water has resulted into deserts in most regions of the world. Most of the deserts are naturally prone to multiple stresses primarily including drought, salinity, temperature extremes, nutrient deficiency, etc. In Pakistan, there are four major deserts, of which Cholistan desert experiences a myriad of environmental stresses causing different types of ecological niches. These specific types of ecological habitats, some rich in high levels of soluble salts, are colonized mainly with a variety of salt tolerant plants. Of them, grasses are of profound importance as they provide fodder to animals being rared within the desert. Moreover, these grasses being tolerant to drought and high temperature, are also highly tolerant to salinity as this menace occurs in patches in between the sand dunes. Salt tolerant grasses have been categorized into different categories from obligate halophytes through less salt tolerant. It is believed that highly salt tolerant grasses have been growing in their native habitats since a long span of time, so they must have evolved with time some prominent adaptive characteristics to tolerate to salinity stress. Most distinctive physio-biochemical and molecular adaptative features in the salt tolerant grasses were recorded to be inclusion of salts, sequestration of salts from the cytosol to the vacuole, retention of salts in roots thereby allowing low quantity of toxic salts to the upper plant parts, excretion of salts from leaf surface, maintenance of high tissue K/Na ratios, and enhanced manifestation of osmoregulation and oxidative defense system. However, the extent of expression of all these physio-molecular traits were found to be positively related with degree of salt tolerance of different grasses. Although considerable efforts are being made to comprehensively characterize and elucidate the mechanisms of salt tolerance in commercial crops using the advanced omics tools such as genomics, transcriptomics, proteomics, metabolomics, ionomics, etc., relatively little work has been done to fully uncover all such mechanisms in these grasses through the advanced technologies. Thus, future research needs to be focused on this issue, because some of these highly salt tolerant grasses are a good source of salt tolerance genes, that can be utilized to improve salinity tolerance of commercial crops.