Maize crop is the third most important cereal crop, mostly grown for food, feed and fodder purpose. In spite of the fact the crop is susceptible to salt stress but exhibits a considerable genotypic variability for salt tolerance. The present study was carried out to determine to which extent the maize genotypes with contrasting morphological traits respond to salt stress. Seven days old seedlings of thirty maize genotypes were exposed to NaCl stress of EC less than 4 (control), equal to 8 and 12 dS m-1 for further 28 days in a temperature controlled greenhouse. The salt stress imposition was completed in two increments every other day from the date of planting. At the age of 35 days, the seedlings were evaluated for contrasting morphological traits. The genotypes exhibited considerable variations for each of the 10 measured morphological and ionic traits. PCA was employed to identify the most suitable morphological trait to be used as selection criterion for salt tolerance. Based on the PCA results, dry shoot weight (DSW) was used to classify thirty maize genotypes into salt-tolerant-T, moderately tolerant-MT and salt sensitive-S groups. Two (2) out of thirty genotypes i.e. SB-9617 and FH-949 had the highest average of percent dry shoot weight (PDSW) values > 70% were classified as salt tolerant (T). The fifteen (15) genotypes showed average of PDSW values in the range of 55-69.9 % were classified as moderately tolerant (MT) by indicating the sequence order of salt tolerance as YH-1898 > MMRI-yellow > S-2002 > FH-988 > FH-1292 > HC-12 > MS-2018 > NCEV-1270-7 > Pahari > Pearl White > FH-1114 > NCEV-1270-3 > Iqbal > NCEV-1297 > DK-6724. However, thirteen (13) out of total thirty (30) genotypes attained the average PDSW values <55% were classified as salt sensitive (S) following the sequence order as NCEV-1530-9 > Composite > FRI-22 > Azam > MS-2015 > P-1543 > Neelum > Afgoi > Malka-2016 > MS-1501 > HNG > NCEV-1270-5 > NCEV-7004. It was also noticed that the declared salt tolerance was positively correlated with dry shoot weight (DSW), shoot length (SL), stem diameter (SD), fresh shoot weight (FSW), fresh root weight (FRW), dry roots weight (DRW), root length (RL), leaf area per plant (LA), number of leaves per plant (NL) and K+/Na+ ratio. The highest positive Pearson correlation coefficients were determined in LA vs SD (r=0.900), DSW vs SD (r=0.899), SL vs DSW (r=0.891), SL vs FSW (r=0.890) and DSW vs FSW (r=0.887). Additionally, the salt tolerant (T) group of genotypes maintained higher K+/Na+ ratios compared to moderately tolerant (MT) and salt sensitive (S) groups. The results clearly showed that dry shoot weight (DSW) could be viable option to classify maize genotypes into different salt tolerance groups and to identify the most suited and best adapted salt tolerant genotype for cultivation in saline soils. Furthermore, this scientific information could help the plant scientists to improve and develop the new salt tolerant cultivar.
This paper is based on the idea that the hydrographical conditions in the Bornholm Basin, and any other basin, can be understood from knowledge of general hydromechanical principles and basin-specific factors. Published results on the variability of the vertical stratification are shown and discussed. Such analyses demonstrate the residence time of water at different depth levels. Different modes of currents forced by winds and by stratification gradients at open vertical boundaries are presented. Vertical mixing is discussed and published results for the Bornholm Basin are shown. An experiment demonstrates that the diffusive properties of the enclosed basin, i.e. below the sill depth of the Słupsk Furrow, can be computed quite well from the horizontal mean vertical diffusivity obtained from historical hydrographical observations. A published two decades long simulation of the vertical stratification shows that the through flow and modification of new deepwater in the Bornholm Basin can be well described based on existing knowledge regarding crucial hydromechanical processes. It also suggests, indirectly, that there should be a weak anticyclonic circulation above the sill depth, which is supported by current measurements.
In pot experiments carried out in 2005 and 2006, tolerance to sodium chloride salinity of 4 cultivars of perennial ryegrass (Lolium perenne) (‘Nira’, ‘Stadion’, ‘Ronija’, ‘Darius’) was studied. Three concentrations of NaCl in medium (earth + sand): 0.0 mM (control); 50 mM; 100 mM, were used in the investigations. In three successive crops of grass, fresh weight yield of leaves, stomatal conductance, photosynthesis intensity, content of chlorophyll and PS II maximum quantum yield (Fv/Fm) were determined. The obtained results showed that perennial ryegrass is a species tolerant to NaCl salinity. Among the studied cultivars, cv. ‘Ronija’ showed the highest tolerance, whereas cv. ‘Nira’ showed the lowest. The growth of perennial ryegrass plants under salinity conditions was limited by low stomatal conductance of leaves and photosynthesis, but not by the photosynthetic activity of chlorophyll and its contents.