Leaf gas films delay salt entry and enhance underwater photosynthesis and internal aeration of Melilotus siculus submerged in saline water

A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M.siculus survived complete submergence of 1 week at low salinity (up to 50molm-3 NaCl), but did not recover following de-submergence from 100molm-3 NaCl. The leaf gas films protected against direct salt ingress into the leaves when submerged in saline water, enabling underwater photosynthesis even after 3d of complete submergence. By contrast, leaves with the gas films experimentally removed suffered from substantial Na+ and Cl- intrusion and lost the capacity for underwater photosynthesis. Similarly, plants in saline water and without gas films lost more K+ than those with intact gas films. This study has demonstrated that leaf gas films reduce Na+ and Cl- ingress into leaves when submerged by saline water - the thin gas layer physically separates the floodwater from the leaf surface. This feature aids survival of plants exposed to short-term saline submergence, as well as the previously recognized beneficial effects of gas exchange under water

A simple and versatile 2-dimensional platform to study plant germination and growth under controlled humidity

We describe a simple, inexpensive, but remarkably versatile and controlled growth environment for the observation of plant germination and seedling root growth on a flat, horizontal surface over periods of weeks. The setup provides to each plant a controlled humidity (between 56% and 91% RH), and contact with both nutrients and atmosphere. The flat and horizontal geometry of the surface supporting the roots eliminates the gravitropic bias on their development and facilitates the imaging of the entire root system. Experiments can be setup under sterile conditions and then transferred to a non-sterile environment. The system can be assembled in 1-2 minutes, costs approximately 8.78$per plant, is almost entirely reusable (0.43$ per experiment in disposables), and is easily scalable to a variety of plants. We demonstrate the performance of the system by germinating, growing, and imaging Wheat (Triticum aestivum), Corn (Zea mays), and Wisconsin Fast Plants (Brassica rapa). Germination rates were close to those expected for optimal conditions

Transfer of the barrier to radial oxygen loss in roots of Hordeum marinum to wheat (Triticum aestivum): evaluation of four H-marinum-wheat amphiploids

Wide hybridization of waterlogging-tolerant Hordeum marinum with wheat (Triticum aestivum) to produce an amphiploid might be one approach to improve waterlogging tolerance in wheat. Growth, root aerenchyma and porosity, and radial oxygen loss (ROL) along roots were measured in four H. marinum–wheat amphiploids and their parents (four accessions of H. marinum and Chinese Spring wheat) in aerated or stagnant nutrient solution. A soil experiment was also conducted. Hordeum marinum maintained shoot dry mass in stagnant nutrient solution, whereas the growth of wheat was markedly reduced (40% of aerated control). Two of the four amphiploids were more tolerant than wheat (shoot dry masses of 59–72% of aerated controls). The porosity of adventitious roots when in stagnant solution was higher in H. marinum (19–25%) and the four amphiploids (20–24%) than in wheat (16%). In stagnant solution, adventitious roots of H. marinum formed a strong ROL barrier in basal zones, whereas, in wheat, the barrier was weak. Two amphiploids formed a strong ROL barrier and two formed a moderate barrier when in stagnant solution. This study demonstrates the transfer of higher root porosity and a barrier to ROL from H. marinum to wheat through wide hybridization and the production of H. marinum–wheat amphiploids.A. I. Malik, A. K. M. R. Islam and T. D. Colme

The effect of saline hypoxia on growth and ion uptake in Suaeda maritima

The widely occurring annual halophyte Suaeda maritima experiences fluctuating salt and oxygen concentration during tidal cycles in salt marshes and shows tolerance of extreme hypoxia. The effect of saline waterlogging on growth and ion accumulation was investigated in tanks in a glasshouse where tidal flow was simulated, and in an aerated and hypoxic saline nutrient solution in a controlled environment cabinet. Laboratory data were compared with data from a survey of growth in two salt marshes. Plants in the nutrient solution grew equally well in the alternative nitrogen sources, NO(3)(-) and NH(4)(+). Hypoxia, produced in the nutrient solution by nitrogen bubbling in the absence of turbulence and using stagnant agar, reduced root growth; hypoxia in waterlogged pot media in the glasshouse also reduced shoot growth and net K(+) uptake but increased net uptake of Na(+) and Cl(-). (22)Na(+) influx into shoots was only significantly reduced by hypoxia when combined with a sudden increase in salt concentration to 200 mM NaCl. S. maritima appears to be well adapted to tolerate severely hypoxic growth conditions