Effect of changed source/sink relations on proteolytic activities and on nitrogen mobilization in field-grown wheat (Triticum aestivum L.)

Nitrogen mobilization and the pattern of proteolytic enzymes were investigated in leaves and glumes of field-grown winter wheat (Triticum aestivum L.) during maturation. Source/sink relations were changed by removal of the ear, the flag leaf or the lower leaves shortly after anthesis. Removal of the ear was most effective, resulting in delayed senescence of the flag leaf with the chlorophyll, aminopeptidase and carboxypeptidase activities remaining high in contrast to the control, whereas neutral endopeptidase activity increased more slowly. No major changes were observed in the second leaf from the top in plants with either ears or flag leaves removed. Nitrogen mobilization and proteolytic activities in glumes and the remaining leaves were influenced only slightly by leaf removal. In earless plants, nitrogen was transported from the second leaf into the leaf sheath and stem, but in the flag leaf the total reduced nitrogen remained high and free amino groups increased. The increase in endopeptidase activity was influenced by the source/sink relations. However, the accumulation of amino groups and the increasing endopeptidase activity in the flag leaf of earless plants suggest that the nitrogen sink capacity did not greatly control protein degradation; it remains to be seen whether phytohormones, accumulated amino acids or other factors delayed the increase in endopeptidase activit

Comparison of flag leaf and ear photosynthesis with biomass and grain yield of durum wheat under various water conditions and genotypes

Photosynthetic activity of cereals has traditionally been studied using leaves, thus neglecting the role of other organs such as ears. Here, we studied the effects of water status and genotypes on the photosynthetic activity of the flag leaf blade and the ear of durum wheat. The various parameters related to the photosynthetic activity were analysed in relation to the total above-ground plant biomass and grain yield at maturity. Four local varieties plus two cultivars adapted to the semiarid areas of South Morocco were grown in pots in a greenhouse. Five different water treatments were maintained from the beginning of stem elongation to maturity, when shoot biomass and grain yield were recorded. The net photosynthesis (A), stomatal conductance (gs) and transpiration (T) of the ear and the flag leaf were measured at anthesis. In both organs these factors decreased significantly with water deficit, whereas the A/T and A/gs ratios increased. The genotype effect was also significant for all traits studied. Whole-organ photosynthesis was much higher in the ear than in the flag leaf in well-watered conditions. As water stress developed, photosynthesis decreased less in the ear than in the flag leaf. Whole-ear photosynthesis correlated better than flag leaf photosynthesis with biomass and yield. Nevertheless, the relationships of the whole flag leaf with biomass and yield improved as the water stress became more severe, suggesting a progressive shift of yield from sink to source limitation. For all water regimes the ratios A/gs and A/T of the ear also showed a higher (negative) correlation with both biomass and yield than those of the flag leaf. The results indicate that the ear has a greater photosynthetic role than the flag leaf in determining grain yield, not only in drought but also in the absence of stress

The phenotypic expression of QTLs for partial resistance to barley leaf rust during plant development

Partial resistance is generally considered to be a durable form of resistance. In barley, Rphq2, Rphq3 and Rphq4 have been identified as consistent quantitative trait loci (QTLs) for partial resistance to the barley leaf rust pathogen Puccinia hordei. These QTLs have been incorporated separately into the susceptible L94 and the partially resistant Vada barley genetic backgrounds to obtain two sets of near isogenic lines (NILs). Previous studies have shown that these QTLs are not effective at conferring disease resistance in all stages of plant development. In the present study, the two sets of QTL–NILs and the two recurrent parents, L94 and Vada, were evaluated for resistance to P. hordei isolate 1.2.1 simultaneously under greenhouse conditions from the first leaf to the flag leaf stage. Effect of the QTLs on resistance was measured by development rate of the pathogen, expressed as latency period (LP). The data show that Rphq2 prolongs LP at the seedling stage (the first and second leaf stages) but has almost no effect on disease resistance in adult plants. Rphq4 showed no effect on LP until the third leaf stage, whereas Rphq3 is consistently effective at prolonging LP from the first leaf to the flag leaf. The changes in the effectiveness of Rphq2 and Rphq4 happen at the barley tillering stage (the third to fourth leaf stages). These results indicate that multiple disease evaluations of a single plant by repeated inoculations of the fourth leaf to the flag leaf should be conducted to precisely estimate the effect of Rphq4. The present study confirms and describes in detail the plant development-dependent effectiveness of partial resistance genes and, consequently, will enable a more precise evaluation of partial resistance regulation during barley developmen

Leaf-applied sodium chloride promotes cadmium accumulation in durum wheat grain

Cadmium (Cd) accumulation in durum wheat grain is a growing concern. Among the factors affecting Cd accumulation in plants, soil chloride (Cl) concentration plays a critical role. The effect of leaf NaCl application on grain Cd was studied in greenhouse-grown durum wheat (Triticum turgidum L. durum, cv. Balcali-2000) by immersing (10 s) intact flag leaves into Cd and/or NaCl-containing solutions for 14 times during heading and dough stages. Immersing flag leaves in solutions containing increasing amount of Cd resulted in substantial increases in grain Cd concentration. Adding NaCl alone or in combination with the Cd-containing immersion solution promoted accumulation of Cd in the grains, by up to 41%. In contrast, Zn concentrations of grains were not affected or even decreased by the NaCl treatments. This is likely due to the effect of Cl complexing Cd and reducing positive charge on the metal ion, an effect that is much smaller for Zn. Charge reduction or removal (CdCl2 0 species) would increase the diffusivity/lipophilicity of Cd and enhance its capability to penetrate the leaf epidermis and across membranes. Of even more significance to human health was the ability of Cl alone to penetrate leaf tissue and mobilize and enhance shoot Cd transfer to grains, yet reducing or not affecting Zn transfer

Effect of Spermine and Spermidine on Wheat Plants Irrigated with Waste Water: Conductive Canals of Flag Leaf and Peduncle in Relation to Grain Yield

A pot experiment was conducted to evaluate the beneficial effect of grain presoaking in spermine (0.15 mM), spermidine (0.3 mM) and their interaction on waste water tolerance of wheat plants (Triticum aestivum L.) variety Sakha 94. In general, waste water caused significant increases in the leaf thickness and ground tissue thickness in flag leaves as well as metaxylem vessel area, xylem vessel area, vascular bundle area in flag leaf and peduncle of main shoot of wheat plants. On the other hand leaf thickness and ground tissue thickness appeared to decrease at concentration 100% of waste water. Irrigation of wheat plants with waste water at all examined concentrations decreased phloem area in flag leaves and peduncle of main shoot of wheat plants. The application of spermine, spermidine or their interaction induced some modifications in the anatomical features of the flag leaf and peduncle of main shoot which appeared to be an adaptive response to heavy metals in applied waste water. Furthermore, Irrigation of wheat plants with waste water stress decreased significantly grain yield / plant. The applied polyamines appeared to alleviate the effect of heavy metals stress in waste water on grain yield. The effect was more pronounced with spermine +spermidine treatment. For anatomical features, the economic yield of wheat plants appeared to be positively correlated with the phloem area but negatively correlated with vascular bundle area and xylem area in flag leaf and peduncle of main shoot

Differences in the Morphological Characteristics of the Land Races of the Soft and Emmer Wheat in Relation to the Modern Varieties

For the organic farmers there is important question which varieties of wheat are right for organic farming in Less Favoured Areas. Modern varieties of wheat are bred in the conditions of conventional (high imput) farming. That is why the organic farmers asked about the suitability of land races of soft wheat (Triticum aestivum L.) or different species like emmer wheat grown in the past (Triticum dicoccum SCHUEBL). The paper results from the study of fourty land races, two intermediate and ten modern varieties of soft wheat in comparison to ten land races of emmer wheat at two locations in the Czech Republic. We evaluated tuft shape, length of plant, length and width of flag leaf, length and density of spike and awnedness. The modern varieties of soft wheat are characterised by a high level of uniformity. Their tuft shape is erect or semi-erect and length of plant is 60-70 cm, it does not rise the weed competitiveness. On the other hand, they have a medium or long flag leaf whose width is narrow or medium. Length of spike is medium or long. On the other hand, emmer wheat land races have the same tuft shape as forgoing modern varieties. Length of plant (89-119 cm) is the positive aspect of the weed competitiveness. Their flag leaf is narrow, but it is compesated by its length. The spike is shorter than the spike of modern varieties of soft wheat, but it is effectivelly compensated by an increased density. Intermediate wheat land races are characterised by looselly spreading tuft shape which puts the weeds down, but on the other hand, it favours the mildew because of the microclimate of soil. Its flag leaf is very short and narrow. Length of spike is medium and it is lax dense. The group of land races of soft wheat is characterised by a high diversity. The tuft shape is most frequently semi-erect. The length of plant varies from 60 to 120 cm, it usually ranges from 90 to 110 cm. Flag leaf is usually long or very long, but its width is very narrow or narrow. The spike is often long, but lax dense. Some of the evaluated varieties of landraces are proved to be suitable for organic farming from the point of view of the morphological characteristics

Morphophyziological and Anatomical Characteristics of Leaves in Accessions of Wild Einkorn (Triticum boeoticum Boiss.)

The aim of this study was to assess the degree of variation between 32 accessions of wild einkorn (Triticum boeoticum Boiss.) on the basic morphophysiological and anatomical characteristics of the flag and subflag leaves. The experiment was carried out during 2016 – 2017 growing seasons in the randomized block design in four replications and 10 m2 plot size. Significant differences among the accessions for all studied characters were recorded. The epidermis of the studied 32 accessions was constructed by strongly elongated prosenhyme cells with flexous walls. The stomatas were with oval to elliptic shape, about 1.5 times longer than wide. The most variable character was the total chlorophyll content. Accessions with numbers B6E0416, B6E0413, B6E0398 and B6E0392 had the largest amount of chlorophyll pigments exceeding the average standard almost twice. The water-to-biomass ratio in the flag leaf was the greatest for B6E0378, B6E0389 and B6E0401, while for the subflag leaves B6E0379, B6E0401 and B6E0385 were with the highest amount of water per unit of dry mass. The correlation between intensity of transpiration and the fresh and dry mass of leaves were slightly negative for flag leaf and slightly positive for subflag leaf. The water content of the subflag leaf had a stronger influence on the morphophysiological parameters compared to the water content of the flag leaf. PC-analysis grouped accessions according to similarity on the basis of investigated morphophysiological and physiological characters in two components in the factor plane

Osmotic adjustment in wheat flag leaf in relation to flag leaf area and grain yield per plant

BackgroundSalinity stress causes ion toxicity and osmotic imbalances, leading to oxidative stress in plants. Antioxidants are considered ameliorators of saline stress and could develop salinity tolerance in crop plants. To ascertain the role of antioxidants in inducing osmotic adjustment in salt stressed wheat flag leaf in terms of compatible solutes accumulation, water relations parameters and osmotic adjustment as well as flag leaf area and grain yield per plant, in addition, flag leaf anatomy were examined.ResultsSalt stress up to 11.5 dSm-1 causes a significant reduction in water potential, osmotic potential, as well as relative water content, and water content. On the other hand, turgor potential and osmotic adjustment were significantly increased due to inducing increasing the higher accumulation of compatible osmolytes which leads to decreasing flag leaf area and grain yield per plant.Application of both antioxidants, in particular, ascorbic acid increased significantly flag leaf area, and grain yield per plant due to osmotic adjustment and maintaining leaf turgor potential as a consequence of increasing leaf water potential, water content and relative water content as compared to control plants. On the other hand, application of both antioxidants under all salinity levels, nullify the harmful effects of salinity on flag leaf area and grain yield per plant due to increasing osmolyte accumulation, maintaining turgor potential and osmotic adjustment.Anatomically, increasing salinity levels decreased thickness of leaf blade at midrib region, thickness of mesophyll tissue, tangential dimension of midrib vascular bundle, thickness of upper and lowerepidermis, thickness of big motor cell, and tangential dimension of big xylem vessel. Treatment with either ascorbic acid or tocopherol at 100 mg/L and their interactions with salinity increased all the above mentioned parameters in both nonsalinized and salinized plants. Ascorbic acid is the most effective in this concern.ConclusionIn conclusion, wheat plants responded to an increased ion influx in their cells by increasing the osmolytes synthesis and accumulation under salt stress, which further increased with antioxidants treatment and helped in maintaining the osmotic balance

Estimates of genetic components and regression analysis for grain yield and various morphological traits in bread wheat (Triticum aestivum L.)

The present study was conducted to estimate the gentic components and regression analysis for grain yield and various morphological traits in bread wheat involving 10 parents and their 45 F1s (half diallel) during 2012- 13 and 2013-14. Significant additive (D) and dominance (H1) variance for the traits indicated that expression of these traits is control by both additive and dominance gene action. Average degree of dominance (H1/D)1/2 were more than unity for the traits (peduncle length, flag leaf area, productive tillers, biological yield, grain yield, harvest index) indicating the preponderance of over dominance gene action. The estimates of h2 were positive and significant for days to ear emergence, peduncle length, productive tillers, biological yield and grain yield indicated dominance of genetic components in F1s. Positive and significant values of F were estimated for days to ear emergence, days to 50% flowering, spike length, flag leaf area and grain yield in F1s indicating the preponderance of dominance and positive genes in the parents involved. The theoretical value (0.25) of (H2/4H1) for all the traits indicated asymmetrical distribution of positive and negative genes. The proportion of dominant and recessive alleles indicated presence of dominant alleles in the parents. The traits showing more than 30% narrow sanse heritability could be rewarding for further improvement in grain yield in bread wheat. Regression analysis indicated that the traits (days to ear emergence, days to 50% flowering, peduncle length, flag leaf area, productive tillers, harvest index, biological yield and grain yield) control by over dominance type of gene action. The parent RAJ 4246 contained maximum dominant genes for days to ear emergence and days to 50% flowering; HD 2733 for spike length and flag leaf area and HD 2824 for productive tillers, biological yield and grain yield used as donors in multiple traits breeding programme to develop high yielding wheat genotypes