Yield Response of Uniculm Wheat (Triticum aestivum L.) to Early and Late Application of Nitrogen: Flag Leaf Development and Senescence

Abstract

Nitrogen (N) supply increased flag leaf area by increasing cell number. N promoted initiation and development of floret primordia. N availability upto ear emergence affected fertile floret number more than spikelet number and increased the number of grains. Late application of nitrogen at 5 days after anthesis increased percentage nitrogen in grains, grain weight and grain number due to its effect on ability of floret to set grain. Larger number of florets and grains provided sink not only for carbon but also for nitrogen accumulation with high nitrogen availability. The accumulation of grain protein depended on the accumulation and partitioning of reduced N accumulated during the vegetative stage of growth and the relative contributions of nitrate assimilation and N redistribution during grain development in low as well as high nitrogen supply. Flag leaf of 'Gigas' wheat retained the ability to synthesize RuBPCO on induction of nitrate reductase by substrate supply at post anthesis stage. The reductions in proteolytic enzymes were coincident with loss of Chl, total soluble protein and nitrate reductase activity from the flag leaves.

Over-Expression of a Tobacco Nitrate Reductase Gene in Wheat (Triticum aestivum L.) Increases Seed Protein Content and Weight without Augmenting Nitrogen Supplying

“…In untransformed wheat, the nitrate reductase activities (NRA) of the leaf tissues [15], [16], basipetal part of the youngest ligule emergent leaf [28], third leaf [44], flag leaf [17] and even shoots [45] were found to be correlated more or less with yield and/or grain (flour) quality. We used the flag leaf for determining NRA and nitrate content of T 1 progeny, because its NRA was significantly correlated with both yield and grain protein content in winter wheat [17].…”

“…Nitrate (NO 3 − ) is the main N source for crops under normal field conditions [9], [12], [13] and its availability strongly affects crop productivity and food quality [14], especially in wheat [15]–[17]. The nitrate up-taken in plant is well known to be first reduced to nitrite and then to ammonium via the Glutamate synthesis cycle (GOGAT cycle) in two successive steps catalyzed by nitrate reductase (EC 1.6.6.1, NR) and nitrite reductase (EC 1.7.7.1, NiR) in cytosol and chloroplast, respectively [18].…”

“…Using biotechnology to introduce and over-express exogenous tobacco NR gene was tested for lowering nitrate content in the leaf and edible organs of dicotyledonous crops [20]–[27], but no information about the effect on seed protein content and grain weight was released. To the best of our knowledge, integration and over-expression of foreign NR gene have not been tested in wheat although its foliar NR activity was demonstrated significantly correlated with yield [17], [28], flour quality [16] and grain protein content [15], [17]. The purpose of the present work was to test whether or not introduction and expression of a foreign NR gene in wheat could increase N use efficiency and hence improve quality and/or yield without augmenting N supply, or could maintain quality and/or yield with a diminished use of N fertilizer.…”

Albumin content in bread wheat (Triticum aestivum L.) and durum wheat (Triticum durum Desf.) as affected by the environment

“…During April the stem elongation occurred, as the most intensive phase of plant growth, when the leaf area increased to five times compared to tillering, and when stages of organogenesis led to the formation of the number of the flowers and their fertility. Flag leaves in wheat, formed at the end of the stem elongation phase, are important part of source -sink relation through photo assimilate partitioning and amino acid remobilization (Kumari, 2011). In March, April and May, the most important climatic variable contributing to the GEI for albumins content was mean temperature (32.1, 32.4 and 42.3 %), and also relative humidity (40.1%) in June for bread wheat (Table 3).…”

“…Similarly, the mass of a thousand grains, as indicator of grain filling, was higher in 2010-2011 for 6.74% (data not shown), when May and June, when wheat grain filling occurred, had lower average daily temperature by 3.9% to 6.6% and higher amount of precipitation by 16.9% to 33.8%, depending on the location, in relation to the 2011-2012 growing season. The effect of high temperatures reduces the accumulation of total carbohydrates and leads to an increase in protein content due to the smaller grain size and dissolution of assimilated nitrogen, which is associated with the duration of the period when the plant is green after flowering (Kumari, 2011). Notes.…”