Nitrogen Deficiency Stress Research Articles

Combining ability of nitrogen deficiency stress indices for plant height in rapeseed varieties

Although an average plant height is more preferable in most of agronomic crops, less reduction of this trait in stress condition makes yield components and seed yield sustainable in rapeseed varieties. Combining ability, heterosis and heritability of plant height at application and non-application of nitrogen environments (Hp and Hs, respectively) and its related stress tolerance indices were detected in half F2 diallel crosses of six spring rapeseed varieties. Significant mean squares of general and specific combining abilities (GCA and SCA) were detected for Hp, Hs, mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI), indicating the importance of additive and non-additive genetic effects for them. A high narrow-sense heritability estimate was exhibited for STI, emphasizing the prime importance of additive genetic effects for this stress tolerance index. A significant correlation among Hp, Hs, MP, GMP and STI showed the efficiency of these stress indices for improving plant height in plant breeding programme. In comparison to SCA effects, most of the crosses had significant high parent heterosis for Hp, Hs and all the stress indices. RGS003 with a significant positive GCA effect of Hs was considered as a suitable parent for improving this trait and most of the combinations of this genotype had significant negative SCA effects.

Heritable alteration in DNA methylation induced by nitrogen-deficiency stress accompanies enhanced tolerance by progenies to the stress in rice ( Oryza sativa L.)

Cytosine methylation is responsive to various biotic- and abiotic-stresses, which may produce heritable epialleles. Nitrogen (N)-deficiency is an abiotic stress being repeatedly experienced by plants. To address possible epigenetic consequences of N-deficiency-stress, we investigated the stability of cytosine methylation in rice ( Oryza sativa L.) subsequent to a chronic (a whole-generation) N-deficiency at two levels, moderate (20 mg/L) and severe (10 mg/L), under hydroponic culture. MSAP analysis revealed that locus-specific methylation alteration occurred in leaf-tissue of the stressed plants (S 0) experiencing either level of N-deficiency, which was validated by gel-blotting. Analysis on three non-stressed self-fed progenies (S 1, S 2 and S 3) by gel-blotting indicated that ca. 50% of the altered methylation patterns in somatic cells (leaf) of the stressed S 0 plants were recaptured in S 1, which were then stably inherited to S 2 and S 3. Bisulfite sequencing of two variant MSAP loci with homology to low-copy retrotransposons on one stressed plant (S 0) and its non-stressed progenies (S 1 and S 2) showed that whereas one locus exhibited limited and non-heritable CHH methylation alteration, the other locus manifested dramatic heritable hypermethylation at nearly all cytosine sites within the assayed region. Intriguingly, when two groups of S 2 plants descended from the same N-deficiency-stressed S 0 plant were re-subjected to the stress, the group inheriting the modified methylation patterns showed enhanced tolerance to the N-deficiency-stress compared with the group bearing the original patterns. Our results thus demonstrate heritability of an acquired adaptive trait in rice, which was accompanied by epigenetic inheritance of modified cytosine methylation patterns, implicating an epigenetic basis underlying the inheritance of an acquired trait in plants.

THE POTENTIAL OF REMOTELY SENSED DATA TO PREDICT WHEAT YIELD UNDER MOISTURE AND NITROGEN DEFICIENCY STRESS

Moisture and nitrogen deficiency are major limiting factors for cereal production in many regions worldwide. Detecting stress in crops at an early growth stage is important if significant reductions in yield are to be averted. In this context, remote sensing has the potential of providing a rapid and accurate tool for precision farming in cereal production. This research was undertaken to investigate the potential of broad band and hyperspectral remote sensing for predicting grain yield of wheat (Triticum aestivum L.) under moisture and nitrogen deficiency stress. A controlled greenhouse experiment was conducted to (i) investigate the influence of moisture and nitrogen induced stress on wheat and the resulting spectral reflectance characteristics at the leaf and canopy scale (ii) assess the effectiveness of different vegetation indices to predict wheat grain yield and (iii) assess the possibility of distinguishing between moisture and nitrogen deficiency stressors. Strong significant correlations between crop grain yield and some vegetation indices were observed. Ratio Vegetation Index (RVI) and Simple Ratio (SR) were found to be sensitive to wheat grain yield (r > 0.80). The correlations with grain yield were found to be strongest at the grain filling stage. Principle Component Analysis (PCA) demonstrated low ability to distinguish between moisture and nitrogen deficiency stress.

Evaluation of In‐Season Nitrogen Management Strategies for Corn Production

Nitrogen is an important and costly input for corn (Zea mays L.) production. With rising prices and environmental concerns, producers are looking for ways to better manage N fertilization. A project designed to evaluate in‐season N management strategies for adjusting N rate was conducted in 30 Iowa cornfields from 2004 to 2006. Nitrogen rates applied preplant or early sidedress (PRE‐N) and corn plant sensing with a chlorophyll meter (CM) to detect N stress was used to determine as‐needed in‐season post sensing nitrogen application (POST‐N). Field‐length strips were replicated three times with six N treatments: zero‐N control, 67 kg N ha−1 (reduced PRE‐N rate), 67+ (reduced PRE‐N rate plus POST‐N), 134 kg N ha−1 (agronomic PRE‐N rate), 134+ (agronomic PRE‐N rate plus POST‐N), and 268 kg N ha−1 (PRE‐N non‐N limiting reference rate). Nitrogen deficiency stress sensing was partially successful, with 70 to 80% correct N deficiency detection. Mean yield increased 0.5 Mg ha−1 across all sites with the POST‐N applied to the 67 kg N ha−1 PRE‐N rate. The 67+ POST‐N strategy had a similar total N applied as the agronomic 134 kg N ha−1 PRE‐N rate, but the yield was 0.5 Mg ha−1 lower. This indicates yield potential loss and poor recovery from the POST‐N applications. Economic return comparisons indicated that the agronomic 134 PRE‐N rate and 134+ POST‐N in‐season strategy were similar and had higher return than the 67+ POST‐N strategy. The agronomic PRE‐N rate, with confirmation of N stress and determination of additional N need through plant sensing, was a more cost effective in‐season strategy than starting with the reduced PRE‐N rate.

Responses of sugar beet ( Beta vulgaris L.) to drought and nutrient deficiency stress

The responses of two sugar beet genotypes, 24367 (putative drought tolerant) and N6 (putative drought intolerant), to drought and nutrient deficiency stress were investigated in an attempt to identify reliable and sensitive indicators of stress tolerance. In glasshouse-grown plants of both genotypes, relative water content (RWC) of the leaves decreased and leaf temperature increased in response to drought stress. Genotype differences in response to drought included leaf RWC, glycine betaine accumulation, alteration of shoot/root ratio and production of fibrous roots. Thus, in comparison to N6, genotype 24367 lost less water from leaves, produced more fibrous roots, produced more glycine betaine in shoots and tap roots and had a much reduced shoot/root ratio in response to withholding water for up to 215 h. The hydraulic conductance and sap flow of sugar beet seedlings grown in nutrient culture decreased when subjected to nitrogen deficiency stress. Under nitrogen sufficient conditions sap flow was greater in 24367 than in N6. The results indicate that genotype 24367 is more tolerant to stresses induced by water and nitrogen deficiency and that increased fibrous root development may be a major factor in increasing sap flow via a concomitant enhancement of aquaporin activity.

Changes in chlorophyll fluorescence quenching and pigment composition in the green alga Chlorococcum sp. grown under nitrogen deficiency and salinity stress

Changes in the in vivo chlorophyll fluorescencequenching, photosynthesis and pigment composition werefollowed in the green alga Chlorococcum sp.during exposure of the culture to nitrogen deficiencyand salinity stress with the aims to study theinterrelations between changes in physiological andphotochemical parameters and xanthophyll-cyclepigments content during adaptation to stress, and toevaluate the capacity of this green alga to producesecondary carotenoids in tubular photobioreactors.Exposure of Chlorococcum to nitrogendeficiency, 0.2 M NaCl and high irradiance outdoorscaused a strong depression of the photosyntheticactivity and of photochemical quantum yield ofPSII (Fv/Fm). These changes wereaccompanied by an increase of the non-photochemicalquenching coefficient (NPQ), of the amount ofxanthophyll-cycle pigments and of thecarotenoid/chlorophyll ratio. As a result of exposureto stress conditions, cell division completelystopped, although an increase in the biomass dryweight could be detected due to an increase in thecell size. These processes were followed, with acertain delay (15–20 h), by massive appearance ofsecondary carotenoids that reached the maximum (about50% total carotenoids) after 2–3 days of cultivation.The results show that despite of the lower carotenoidcontent (2 mg g-1 dry wt) as compared with Haematococcus, Chlorococcum can be apotentially interesting strain for secondarycarotenoid production because of its higher growthrate.

Effects of nitrogen deficiency and soil moisture stress on growth of pasture grasses at Samford, south-east Queensland. 1. Results of field experiments

Two field experiments were carried out at Samford during 1958, 1959, and 1960 using three grasses, nitrogen fertilizer, and supplementary irrigation. Attention was concentrated on grass growth during September to December, a period that is particularly important for livestock that have been grazed on poor quality feed during winter. Nitrogen deficiency was more important than soil moisture stress in limiting growth of grass under natural rainfall. Nitrogen fertilizer caused large increases in yield each year, and maximum yields above 10,000 lb of d y matter an acre were produced by uninterrupted growth up to December or January-four or five times the yields of the unertilized plots. Differences between the yields of the three grasses were small compared with the size of the nitrogen response. In the spring of 1960-61, which was the driest of the three seasons during this investigation, soil moisture stress reduced growth of nitrogen-fertilized Rhodes grass (Chloris gayana Kunth.) up to mid-December one-third. It was observed that fertilized Rhodes grass withdrew water more rapidly and to a greater depth than Rhodes grass without added nitrogen.

Effects of nitrogen deficiency and soil moisture stress on growth of pasture grasses at Samford, south-east Queensland. 2. Calculation of the expected frequency of dry periods by a water budget analysis

A water-budget analysis was carried out using the Penman formula to assess the long-term effectiveness of rainfall at Samford. The analysis successfully predicted the occurrence of every important period of soil moisture stress that was recorded by direct measurement during a field experiment. It tended to over-estimate the length of dry periods, but the calculated drought days were related reasonably closely to effects on grass growth. Analysis of 100 years' rainfall, using the records for Brisbane and Samford, predicted that periods of soil moisture stress will occur during the months of October, November and December in slightly more than half the years at Samford. It was calculated that the average effect of dry weather between September 1 and December 1 would be to reduce yields of nitrogen-fertilized Rhodes grass (Chloris gayana Kunth.) by about 20 per cent. A major depression of yield by, drought, i.e. a reduction to less than 50 per cent of yield with adequate water, is expected with an average frequency of slightly less than 1 year in 10. Under the climatic conditions of Samford there seems to be little justification for supplementary irrigation of nitrogen- fertilized grasses. It is suggested that water resources could be better used on pasture legumes such as white clover.