Elevated CO2 accelerates flag leaf senescence in wheat due to ear photosynthesis which causes greater ear nitrogen sink capacity and ear carbon sink limitation

2009 ◽  
Vol 36 (4) ◽  
pp. 291 ◽  
Author(s):  
Chunwu Zhu ◽  
Jianguo Zhu ◽  
Qing Zeng ◽  
Gang Liu ◽  
Zubing Xie ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Leaf Senescence ◽  
Carbon Sink ◽  
Flag Leaf ◽  
Net Photosynthesis ◽  
Grain Filling ◽  
Flag Leaves ◽  
Sink Capacity ◽  
Sink Limitation ◽  
Grain Nitrogen

It was anticipated that wheat net photosynthesis would rise under elevated CO2, and that this would alter the progress of senescence due to the unbalance of carbohydrates and nitrogen. Our study showed that ear carbon sink was limited, and sugar was accumulated, hexokinase activities and levels of phosphorylated sugar were increased within the flag leaves, grain nitrogen sink capacity was enhanced, and flag leaf senescence was accelerated under elevated CO2. However, if the ear of the main stem was covered, these responses to elevated CO2 were absent, and the senescence of flag leaf was not accelerated by elevated CO2. Thus, it appeared that elevated CO2 accelerated the rate of flag leaf senescence, depending on ear photosynthesis. The ears have far higher enhancement of net photosynthesis than flag leaves, and the role of the flag leaf relative to the ear was declined in supplying C assimilation to grain under elevated CO2. This indicates that as CO2 rises, the grain sink needs the N more than C assimilate from flag leaf, so the declining rates of N% and soluble proteins concentration were markedly accelerated under elevated CO2 conditions. This suggests that, the large increase in ear net photosynthesis accelerated grain filling, accelerated remobilising N within flag leaf as the result of the greater grain nitrogen sink capacity. In addition, as the result of grain carbon sink limitation, it limited the export of flag leaf sucrose and enhanced sugar cycling, which was the signal to accelerate leaf senescence. Hence, elevated CO2 subsequently accelerates senescence of flag leaf.

POTENTIAL NET PHOTOSYNTHESIS IN FLAG LEAVES OF SEVERELY DROUGHT-STRESSED WHEAT CULTIVARS AND ITS RELATIONSHIP TO GRAIN YIELD

1974 ◽  
Vol 54 (4) ◽  
pp. 811-815 ◽  
Author(s):  
R. KAUL
Keyword(s):  
Desiccation Tolerance ◽  
Flag Leaf ◽  
Assimilation Efficiency ◽  
Relative Yield ◽  
Net Photosynthesis ◽  
Grain Filling ◽  
Triticum Aestivum L ◽  
Wheat Cultivars ◽  
Water Deficits ◽  
Flag Leaves

Six wheat cultivars grown in the field in 1973 showed continuously increasing water deficits which attained severe levels by the end of the season. The relative yield performance of five Triticum aestivum L. cultivars was predictable from the integrated net photosynthetic potential of their flag leaves. Grain productivity of a T. durum L. cultivar, Pelissier, was uniformly underestimated, likely because of poor desiccation tolerance of its flag leaf. It is suggested that Pelissier depended on the longevity of its heavily awned spike for additional grain filling. Results show that photosynthetic desiccation tolerance in severely stressed flag leaves of Pitic 62 ranks above that of Manitou, Cypress, and particularly Selkirk and Pelissier. Glenlea was comparable to Manitou and Cypress in flag leaf assimilation efficiency when subjected to early drought hardening, but exhibited less efficiency when subjected to water deficits late in development.

Rate and duration of grain filling in relation to flag leaf senescence and grain yield in spring wheat (Triticum aestivum) exposed to different concentrations of ozone

2008 ◽  
Vol 110 (3) ◽  
pp. 366-375 ◽  
Author(s):  
Johanna Gelang ◽  
Håkan Pleijel ◽  
Ebe Sild ◽  
Helena Danielsson ◽  
Suhaila Younis ◽  
...  
Keyword(s):  
Triticum Aestivum ◽  
Grain Yield ◽  
Leaf Senescence ◽  
Spring Wheat ◽  
Flag Leaf ◽  
Grain Filling

scholarly journals Nitrogen deficiency regulates premature senescence by modulating flag leaf function, ROS homeostasis, and intercellular sugar concentration in rice during grain filling

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Shamsu Ado Zakari ◽  
Syed Hassan Raza Zaidi ◽  
Mustapha Sunusi ◽  
Kabiru Dawaki Dauda
Keyword(s):  
Grain Yield ◽  
Leaf Senescence ◽  
Flag Leaf ◽  
Grain Filling ◽  
Sugar Concentration ◽  
Premature Senescence ◽  
N Supply ◽  
Ros Homeostasis ◽  
N Assimilation ◽  
N Deficiency

Abstract Background Leaf senescence occurs in an age-dependent manner, but the rate and timing of leaf senescence may be influenced by various biotic and abiotic factors. In the course of stress, the function, composition, and different components of photosynthetic apparatus occur to be synthesized homogeneously or degraded paradoxically due to different senescence-related processes. Nitrogen (N) deficiency is one of the critical environmental factors that induce leaf senescence, and its incidence may curtail leaf photosynthetic function and markedly alter the genetic information of plants that might result in low grain yield. However, the physiological and genetic mechanism underlying N deficiency regulates premature senescence, and flag leaf function, ROS homeostasis, and intercellular sugar concentration in rice during grain filling are not well understood. In this paper, Zhehui7954 an excellent indica restorer line (wildtype) and its corresponding mutant (psf) with the premature senescence of flag leaves were used to study the effect of different N supplies in the alteration of physiological and biochemical components of flag leaf organ and its functions during grain filling. Results The results showed that the psf mutant appeared to be more susceptible to the varying N supply levels than WT. For instance, the psf mutant showed considerably lower Pn, Chl a, Chl b, and Car contents than its WT. N deficiency (LN) decreased leaves photosynthetic activities, N metabolites, but significantly burst O2•−, H2O2, and relative conductivity (R1/R2) concentrations, which was consistent with the expression levels of senescence-associated genes. Sucrose, glucose, and C/N ratio concentrations increased with a decrease in N level, which was closely associated with N and non-structural carbohydrate translocation rates. Increases in POD activity were positively linked with the senescence-related enhancement of ROS generation under LN conditions, whereas, SOD, CAT, and APX activities showed opposite trends. High N (HN) supply significantly inhibits the transcripts of carbohydrate biosynthesis genes, while N assimilation gene transcripts gradually increased along with leaf senescence. The psf mutant had a relatively higher grain yield under HN treatment than LN, while WT had a higher grain yield under MN than HN and LN. Conclusions This work revealed that the C/N ratio and ROS undergo a gradual increase driven by interlinking positive feedback, providing a physiological framework connecting the participation of sugars and N assimilation in the regulation of leaf senescence. These results could be useful for achieving a higher yield of rice production by appropriate N supply and plant senescence regulation.

Effects of varying nitrogen supply at different stages of the reproductive phase on spikelet and grain production and on grain nitrogen in wheat

1973 ◽  
Vol 24 (5) ◽  
pp. 647 ◽  
Author(s):  
RHM Langer ◽  
FKY Liew
Keyword(s):  
Leaf Area ◽  
Flag Leaf ◽  
Grain Filling ◽  
Solution Culture ◽  
Nitrogen Supply ◽  
Nitrogen Application ◽  
Stage Number ◽  
Leaf Area Duration ◽  
Three Stages ◽  
Grain Nitrogen

Plants of wheat cv. Arawa confined to the main shoot were grown in solution culture in a glasshouse. Nitrogen supply was either high (150 p.p.111.) or low (15 p.p.m.) at three stages of development: between the double-ridge stage and floret initiation, between then and ear emergence, or after ear emergence, giving eight treatment combinations. Spikelet numbers were increased only by raising nitrogen supply at the doubleridge stage. Number of grains per spikelet also responded to treatment during the same period, but was greatest when high nitrogen was given until ear emergence. This response depended on the position of the spikelet within the ear, and the basal and terminal spikelets contributed least when nitrogen supply was low. Individual grain weight responded less to treatment than grain numbers. Nitrogen application had a large effect on leaf area duration, but the grain/leaf ratio (G) was depressed. Since their appeared to be no nitrogen effects on photosynthesis per unit flag leaf area, it is suggested that grain yield was controlled mainly by the capacity of the ear to accept carbohydrate, depending on the number of sites available for grain filling. Percentage grain nitrogen increased with lateness of nitrogen application. However, raising nitrogen supply before ear emergence and then decreasing it again also affected grain nitrogen in the ear, which suggests redistribution during grain filling

scholarly journals Differential Flag Leaf and Ear Photosynthetic Performance Under Elevated (CO2) Conditions During Grain Filling Period in Durum Wheat

2020 ◽  
Vol 11 ◽  
Author(s):  
Angie L. Gámez ◽  
Rubén Vicente ◽  
Rut Sanchez-Bragado ◽  
Iván Jauregui ◽  
Rosa Morcuende ◽  
...  
Keyword(s):  
Triticum Turgidum ◽  
Tricarboxylic Acid Cycle ◽  
Flag Leaf ◽  
Grain Filling ◽  
Good Evidence ◽  
Sugar Accumulation ◽  
Flag Leaves ◽  
Gross Photosynthesis ◽  
Respiration Rates ◽  
The Impact

Elevated concentrations of CO2 (CO2) in plants with C3 photosynthesis metabolism, such as wheat, stimulate photosynthetic rates. However, photosynthesis tends to decrease as a function of exposure to high (CO2) due to down-regulation of the photosynthetic machinery, and this phenomenon is defined as photosynthetic acclimation. Considerable efforts are currently done to determine the effect of photosynthetic tissues, such us spike, in grain filling. There is good evidence that the contribution of ears to grain filling may be important not only under good agronomic conditions but also under high (CO2). The main objective of this study was to compare photoassimilate production and energy metabolism between flag leaves and glumes as part of ears of wheat (Triticum turgidum L. subsp. durum cv. Amilcar) plants exposed to ambient [a(CO2)] and elevated [e(CO2)] (CO2) (400 and 700 μmol mol–1, respectively). Elevated CO2 had a differential effect on the responses of flag leaves and ears. The ears showed higher gross photosynthesis and respiration rates compared to the flag leaves. The higher ear carbohydrate content and respiration rates contribute to increase the grain dry mass. Our results support the concept that acclimation of photosynthesis to e(CO2) is driven by sugar accumulation, reduction in N concentrations and repression of genes related to photosynthesis, glycolysis and the tricarboxylic acid cycle, and that these were more marked in glumes than leaves. Further, important differences are described on responsiveness of flag leaves and ears to e(CO2) on genes linked with carbon and nitrogen metabolism. These findings provide information about the impact of e(CO2) on ear development during the grain filling stage and are significant for understanding the effects of increasing (CO2) on crop yield.

Studies of grain production in Sorghum bicolor (L. Moench). VII.* Contribution of plant parts to canopy photosynthesis and grain yield in field stations

1976 ◽  
Vol 27 (2) ◽  
pp. 235 ◽  
Author(s):  
KS Fischer ◽  
GL Wilson ◽  
I Duthie
Keyword(s):  
Grain Yield ◽  
Flag Leaf ◽  
Net Photosynthesis ◽  
Grain Filling ◽  
Carbon Dioxide Exchange ◽  
Relative Importance ◽  
Leaf Position ◽  
Canopy Photosynthesis ◽  
Photosynthetic Rates ◽  
Plant Parts

A method based on 14CO2 uptake and carbon dioxide exchange in sorghum canopies at medium and high density populations allowed the estimation of photosynthesis by plant parts (heads, and leaves at each level of insertion) after anthesis. The relative importance of corresponding parts did not differ between populations, nor did photosynthetic rates per unit leaf area. The latter did decline with successive leaf position down the canopy but were generally compensated by increasing area of these leaves. Averaged over the two populations, which differed little, the heads provided 14% of canopy photosynthesis, and the flag leaf and leaves 2, 3 and 4 were responsible for 21, 24, 21 and 13% respectively. Greater leaf areas per unit land area in the higher population, for each leaf position, resulted in higher total canopy photosynthesis. Previous studies having shown that net photosynthesis after heading corresponds closely to grain yield, the relative importance of plant parts to overall net photosynthesis may be regarded as their relative contribution to grain filling. A direct estimate of their importance in this regard, based on another method, showed the head to contribute 17%, and the next four leaves 17, 25, 20 and 17%. Factors controlling photosynthetic rates of parts are discussed, and the estimates of the importance of photosynthetic sites to grain filling are compared with those reported in previous work. _____________________ *Part VI, Aust. J. Agric. Res., 27: 35 (1976).

COMPARATIVE DATA ON THE RATE OF PHOTOSYNTHESIS, RESPIRATION, AND TRANSPIRATION OF DIFFERENT ORGANS IN AWNED AND AWNLESS ISOGENIC LINES OF WHEAT

1972 ◽  
Vol 52 (6) ◽  
pp. 965-971 ◽  
Author(s):  
I. D. TEARE ◽  
J. W. SIJ ◽  
R. P. WALDREN ◽  
S. M. GOLTZ
Keyword(s):  
Flag Leaf ◽  
Wheat Yield ◽  
Net Photosynthesis ◽  
Triticum Aestivum L ◽  
Isogenic Line ◽  
Photosynthetic Rates ◽  
Flag Leaves ◽  
Isogenic Lines ◽  
Respiration Rates ◽  
The Difference

Net photosynthesis, respiration, and transpiration were determined on heads and flag leaves of two isogenic lines of wheat (Triticum aestivum L. em Thell) by measuring the difference in CO2 and water-vapor concentrations between the incoming and outgoing air streams of an open cuvette system. Net photosynthetic rates (mg CO2 dm−2 hr−1) of the awnless, awned, and awned-clipped heads were not significantly different, but the amount of photosynthesis (mg CO2 hr−1) per head was greater for the awned than for the awnless isogenic line. Net photosynthetic rates of the heads were 20–26% of the net photosynthetic rates of the flag leaves. Respiration rates were nearly two times greater for the awnless and awn-clipped heads than for the awned head. Respiration rates of the heads were 1.7 and 3.0 times greater than the respiration rates of the flag leaves of the awned and awnless isogenics, respectively. Transpiration per head was 34 and 43% of the transpiration per flag leaf for awnless and awned isogenics, respectively. Comparing P/T ratios showed that the awnless isogenic head had a 20% greater water-use efficiency than the awned. This study not only confirmed the work of others, by associating awnedness with increased wheat yield, but also showed how the chlorophyll-containing area of the head is related to photosynthesis, respiration, and transpiration.

Rate and duration of grain filling in relation to flag leaf senescence and grain yield in spring wheat (Triticum aestivum) exposed to different concentrations of ozone

2000 ◽  
Vol 110 (3) ◽  
pp. 366-375 ◽  
Author(s):  
Johanna Gelang ◽  
Hakan Pleijel ◽  
Ebe Sild ◽  
Helena Danielsson ◽  
Suhaila Younis ◽  
...  
Keyword(s):  
Triticum Aestivum ◽  
Grain Yield ◽  
Leaf Senescence ◽  
Spring Wheat ◽  
Flag Leaf ◽  
Grain Filling
Sign in / Sign up

Export Citation Format

Share Document