In vitro saline sodic status of Camelina sativa cv. Blaine creek

Abstract

Salinity causes the disruption of the homeostatic balance of water potential and ion distribution in plants resulting in decreased availability of water to root cells and the plants tend to accumulate high concentrations of Na+ and Clin their vacuoles to protect their cytoplasmic water potential and metabolic imbalances. These metabolic imbalances cause oxidative stress1 and increased production of reactive oxygen species (ROS) – hydrogen peroxide (H2O2), hydroxyl radical (OH), and superoxide ions.2 Scavenging of ROS in plant cells occurs by an endogenous protective mechanism involving antioxidant molecules and enzymes.3,4 On the other hand, it is well known that current world population of 7.6 billion is expected to reach 8.6 billion in 2030, 9.8 billion in 2050 and 11.2 billion in 2100, according to a new United Nations report being launched today.5 The world economy grew by 2.6 percent a year to almost double in size between 1990 and 2014. During that period, global economic growth was driven mainly by low-income and middle-income countries, whose gross domestic product (GDP) grew by some 5.1 percent annually. China’s GDP grew at double that rate, by more than 10 percent year, and in 2014 the country accounted for 9 percent of global GDP, compared to just 2 percent in 1990.6 Salinity is one of the most severe environmental factors limiting the productivity of agricultural crops, because most crops are sensitive to salinity induced by high concentrations of salts in the soil.7 This brief presentation of data suggests that salt tolerant plants should be taken into consideration, since they could play an important role in biosaline agriculture.8 It also reduces photosynthetic activity by destruction of green pigments, lowering leaf area or by decreasing the activity of photosynthetic enzymes. Further, salinity affects the cell membranes and causes lipid peroxidation leading to higher accumulation of malondialdehyde (MDA).9 Soil salinity presents a notable challenge to agriculture, which may be a consequence of human activities, such as irrigation, or alterations in rainfall patterns that reduce leaching of salts and minerals from soils. Lands that were once highly fertile have become less productive due to increased salt levels.10 Furthermore, increasing pressure to use marginal lands for farming often means that growers struggle with naturally-occurring high levels of salt.11 The effect of salt on plant growth and productivity is dependent on salt type, concentration, sensitivity of the crop, and the capacity of the plants to tolerate or mitigate the effects of salts alone or in combination.12 For example, exposure to salt alters differentiation of the Casparian strip causing it to be unusually close to the root meristem13 which changes root architecture14 and the root gravitrophic response, halotropism.15 In addition, cell cycle inhibition as a result of salt stress causes cells in the meristem to stop dividing; cells elongate at the root tip, but do not divide16 and root size is reduced.17 The interest in the study of halophytes is still argued by theoretical reasons, and especially by the current context of human condition, regarded as a well-defined part of surrounding environment. Salinity has affected agriculture from millennia, having a deeply negative impact in agriculture and most likely, being involved in the fall of some ancient flourishing civilizations.8 Of the cultivated lands, about 340 million ha (23%) are saline (salt affected) and another 560 million ha (37%) are sodic (sodium-affected).18 Here are many different projections, suggesting that human population will increase over 8 billion by the year 2020 that will worsen the current scenario about food insecurity.19 There are often not sufficient reservoirs of freshwater available and most of the agronomical used irrigation systems are leading to a permanent increase in soil-salinity and slowly to growth conditions unacceptable for most of the common crops.20 Moreover, salinity causes an increase in the concentration of some leaf osmolites such as proline, betaine and free and bound polyamines.21 A previous study carried out by our group22 on a high oleic sunflower hybrid showed the oleic acid content to increase and the linoleic acid content to decrease with salinity increase.