Stomatal Adjustment to Water Deficits in Three Tropical Grasses and a Tropical Legume Grown in Controlled Conditions and in the Field

1985 ◽  
Vol 12 (2) ◽  
pp. 131 ◽  
Author(s):  
MM Ludlow ◽  
MJ Fisher ◽  
JR Wilson
Keyword(s):  
Soil Water ◽  
Field Experiments ◽  
Panicum Maximum ◽  
Water Deficits ◽  
Buffel Grass ◽  
Heteropogon Contortus ◽  
Tropical Legume ◽  
Controlled Conditions ◽  
Leaf Photosynthetic Rate ◽  
Response To Water

Stomatal conductance (g) and leaf photosynthetic rate (P) of many species in the field are often less sensitive to water deficits than when grown in small pots under controlled conditions. This may result from stomatal adjustment in field-grown plants in response to water deficits that develop slowly, whereas adjustment does not occur under the rapid drying experienced by plants in small pots. To test this hypothesis we studied the response to water potential (Ψl) of g and P in three tropical C4 grasses, green panic (Panicum maximum var. trichoglume), buffel grass (Cenchrus ciliaris) and spear grass (Heteropogon contortus) and a tropical legume, Siratro (Macroptilium atropurpureum), grown under controlled conditions and in the field. Field experiments clearly showed that stomatal adjustment occurred so that g and P were progressively less sensitive to the decline in Ψl as water deficits increased during a long soil drying cycle. For example in one experiment, the Ψl at which P approached zero fell from - 1.9, -2.0 and -2.4 MPa to -4.0, -4.0 and -3.3 MPa for green panic, spear grass and buffel grass, respectively. This stomatal adjustment was reversed within 10 days after rewatering to the well watered condition. Little stomatal adjustment occurred in plants grown under controlled conditions in small pots in which both soil water and Ψl fell rapidly. However, if plants were grown in similar conditions but in large pots of soil so that soil water and Ψl decreased slowly, stomatal adjustment comparable with field-grown plants was observed. Siratro showed much less stomatal adjustment than the grasses and Ψl at which P approached zero only fell from - 1.2 to - 1-5 MPa.

Adaptation to Water Stress of the Leaf Water Relations of Four Tropical Forage Species

1980 ◽  
Vol 7 (2) ◽  
pp. 207 ◽  
Author(s):  
JR Wilson ◽  
MM Ludlow ◽  
MJ Fisher ◽  
E Schulze
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Water Relations ◽  
Bound Water ◽  
Leaf Tissue ◽  
Dry Weight ◽  
Panicum Maximum ◽  
Soil Drying ◽  
Buffel Grass ◽  
Heteropogon Contortus

Three tropical grasses, green panic (Panicum maximum var, trichoglume), spear grass (Heteropogon contortus) and buffel grass (Cenchrus ciliaris) and the tropical legume siratro (Macroptilium atropurpureum), were grown in plots in a semi-arid field environment. The water relations characteristics of leaves from plants subjected to a soil drying cycle were compared with those of unstressed leaves from plants in irrigated plots. Minimum water potentials attained in the stressed leaves were c. -44, - 38, - 33 and - 13 bar for the four species, respectively. The grass leaves adjusted osmotically to water stress, apparently through accumulation of solutes, so that there was a decrease in osmotic potential at full turgor (Ψπ100) of 5.5, 3.9 and 7.1 bar, and in water potential at zero turgor (Ψ0) of 8.6, 6.5 and 8.6 bar for green panic, spear grass and buffel respectively. Water stress appeared to increase slightly the proportion of bound water (B) and the bulk modulus of elasticity (ε) of the grass leaves, but it did not alter the relative water content at zero turgor (RWC0) or the ratio of turgid water content to dry weight of the tissue. The Ψπ100 and Ψ0 of stressed siratro leaves decreased by 2.5-4 bar and 3-5 bar respectively when subjected to soil drying cycles. These changes could be explained by the marked decrease in the ratio of turgid water content to dry weight of the leaf tissue rather than by accumulation of solutes. The values of RWC0 and ε for siratro leaves were not altered by stress but, in contrast to the grasses, B was apparently decreased although the data exhibited high variability. Adjustments in Ψπ100 and Ψ0 of stressed leaves of buffel grass and siratro were largely lost within 10 days of rewatering.

scholarly journals Onion Response to Water Stress

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 837D-837
Author(s):  
Clinton C. Shock ◽  
Erik B.G. Feibert ◽  
Lamont D. Saunders
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Marketable Yield ◽  
Water Deficits ◽  
Yield And Quality ◽  
Highly Sensitive ◽  
Granular Matrix ◽  
Response To Water

Six soil water potential irrigation criteria (–12.5 to –100 kPa) were examined to determine levels for maximum onion yield and quality. Soil water potential at 0.2-m depth was measured by tensiometers and granular matrix sensors (Watermark Model 20055, Irrometer Co., Riverside, Calif.). Onions are highly sensitive to small soil water deficits. The crop needs frequent irrigations to maintain small negative soil water potentials for maximum yields. In each of 3 years, yield and bulb size increased with wetter treatments. In 1994, a relatively warm year, onion yield and bulb size were maximized at –12.5 kPa. In 1993, a relatively cool year, onion marketable yield peaked at –37.5 kPa due to a significant increase in rot during storage following the wetter treatments.

Agronomic and Physiological Responses of Soybean and Sorghum Crops to Water Deficits I. Growth, Development and Yield

1978 ◽  
Vol 5 (2) ◽  
pp. 159 ◽  
Author(s):  
GA Constable ◽  
AB Hearn
Keyword(s):  
Soil Water ◽  
Physiological Responses ◽  
Dry Weight ◽  
Grain Filling ◽  
Water Deficits ◽  
Factors Affecting ◽  
Growth Development ◽  
Response To Water ◽  
Area Development ◽  
Leaf Area Development

The aim of the work reported in this series of four papers was a better understanding of crop response to water deficits in an area where water available for irrigation is limited. In part I, data on the effect of frequency of irrigation, applied post-flowering, on the growth, leaf area development and yield of soybean, cvv. Bragg and Ruse, and sorghum, cv. TX610, are evaluated. Sorghum outyielded both irrigated and rainfed soybeans (5400 versus 2800 and 1800 kg ha-1, respectively). Soil water deficits during pod filling in soybeans caused early leaf death and cessation of pod filling, thus decreasing yield. Irrigation at approximately 90 mm and 135 mm soil water deficit resulted in similar yields. In sorghum and in Ruse soybeans, there was a significant (17-25%) loss in stem dry weight during grain filling, which may have been caused by the relocation of stored assimilates. In Bragg soybeans, only the rainfed plants had a loss in stem dry weight during grain filling. Differences in crop dry weight occurred later than predicted by photosynthesis measurements. Several factors could have contributed to this discrepancy, and we highlight the need for a greater understanding of the contribution from lower leaves and also of the factors affecting the storage and remobilization of reserve assimilates during grain filling.

Genetic variability in sunflower cultivars under drought. I. Yield relationships

1986 ◽  
Vol 37 (6) ◽  
pp. 573 ◽  
Author(s):  
E Fereres ◽  
C Gimenez ◽  
JM Fernandez
Keyword(s):  
Field Experiments ◽  
Yield Component ◽  
Yield Potential ◽  
High Yield ◽  
Seed Number ◽  
Water Deficits ◽  
Viable Seeds ◽  
Yield Responses ◽  
Response To Water ◽  
High Yield Potential

Field experiments were conducted between 1981 and 1983 at Cordoba, Spain, to evaluate the yield responses to drought of 53 sunflower genotypes. There was substantial variability among genotypes both in dryland yield and in yield potential, estimated as the yield under frequent irrigation. No association was found between yield potential and the drought susceptibility index, suggesting that drought resistance and high yield potential may be combined in improved sunflower cultivars. Water deficits reduced harvest index (HI) in all genotypes but the decrease in HI varied among genotypes. Excellent correlations were found between HI and grain yield under dryland conditions for genotypes with similar length of season. The reduction in HI due to water deficits was mostly due to adjustments in seed number with less variation in individual seed weight. In turn, the reduction in seed number was due to a combination of reduced head size and of the area having viable seeds. The length of season of the genotypes apparently affected the yield component adjustments in response to water deficits.

Leaf water potentials of pasture plants in a semi-arid subtropical environment

1975 ◽  
Vol 15 (76) ◽  
pp. 645 ◽  
Author(s):  
DCI Peake ◽  
GD Stirk ◽  
EF Henzell
Keyword(s):  
Water Stress ◽  
Leaf Water ◽  
Panicum Maximum ◽  
Research Station ◽  
Buffel Grass ◽  
Heteropogon Contortus ◽  
Drought Avoidance ◽  
Water Potentials ◽  
Severe Water Stress ◽  
Pasture Plants

Leaf water potentials (�1) were measured on pasture plants at the Narayen Research Station in southern Queensland. The main findings were: 1. There were marked differences between species in the value of �1, measured during drought. Lucerne (Medicago sativa cv. Hunter River) and buffel grass (Cenchrus ciliaris cv. Biloela) usually showed a lower (i.e. more negative) �1 than Siratro (Macroptilium atropurpureum cv. Siratro), when they were grown together in a mixed pasture. Siratro seemed to possess a useful degree of drought avoidance. High drought resistance was observed in buffel grass; this was attributed to its tolerance of water stress. Green panic (Panicum maximum var. trichoglume cv. Petrie) was found to have as low a �1 as lucerne during drought when the two species were grown with Siratro in a mixed pasture. 2. The plants were under severe water stress before all the available water was removed from the deeper soil horizons. 3. �1 was lower in nitrogen-fertilized buffel grass or spear grass (Heteropogon contortus), than in the corresponding unfertilized controls. 4. The vapour-exchange and dye-marker densiometric methods gave different values for �1 in buffel grass, green panic and Siratro; the vapour exchange technique recorded lower, i.e, more negative figures than the other method when the plants were under severe water stress. The two methods gave similar values for lucerne. The relation between the values obtained for buffel grass by the two methods was affected by nitrogen fertilization. The reaction of sown pasture plants to drought at Narayen is discussed.

Changes in Levels of Solutes During Osmotic Adjustment to Water Stress in Leaves of Four Tropical Pasture Species

1981 ◽  
Vol 8 (1) ◽  
pp. 77 ◽  
Author(s):  
CW Ford ◽  
JR Wilson
Keyword(s):  
Water Stress ◽  
Organic Acids ◽  
Osmotic Adjustment ◽  
Inorganic Ions ◽  
Arid Environment ◽  
Low Molecular Weight ◽  
Panicum Maximum ◽  
Buffel Grass ◽  
Heteropogon Contortus ◽  
Macroptilium Atropurpureum

Three tropical grasses, green panic (Panicum maximum var. trichoglume), buffel grass (Cenchrus ciliaris), and spear grass (Heteropogon contortus), and a tropical legume, siratro (Macroptilium atropurpureum), were field-grown in a semi-arid environment. One set of plants was well watered, while another set was subjected to a continuous 35-day drying cycle. Samples of specific leaves were taken at the beginning, middle and end of the drying cycle, and 1, 5 and 14 days after rewatering. The major low-molecular-weight solutes which accumulated in the grasses during water stress were the inorganic ions sodium (green panic), potassium (buffel and spear grass) and chloride (all grasses). Accumulation of these ions largely accounted for the osmotic adjustments determined from a previous study of water relations of the leaves. Concentrations of the minor constituents glucose and fructose increased only slightly in the stressed grasses, whereas levels of sucrose, the major carbohydrate component, increased substantially, particularly in spear grass. Inositol accumulated to a small extent in spear grass. Differences between the grasses were evident in the organic acid spectrum and also in changes in concentration of organic acids due to water stress. In water-stressed tissue, malate levels increased in green panic and spear grass but were reasonably constant in buffel grass. Aconitate concentrations (not detected in buffel grass) decreased in stressed green panic, but increased in spear grass. Oxalate (only trace quantities in spear grass) was a major component in green panic and buffel grass, but did not appear to vary with increase in water stress. Succinate accumulated only in stressed spear grass. The contribution of carbohydrates and organic acids to the osmotic adjustment was relatively small. Proline accumulated to varying degrees in all stressed grasses. Betaine occurred only in trace amounts in spear grass, but accumulated substantially in green panic and buffel grass. Water-stressed leaves of siratro did not accumulate inorganic ions, sugars, organic acids, proline or betaine, but pinitol levels increased. Implications of the results relating osmotic adjustment to changes in chemical composition are discussed.

scholarly journals Large-scale transcriptomics to dissect 2 years of the life of a fungal phytopathogen interacting with its host plant

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Elise J. Gay ◽  
Jessica L. Soyer ◽  
Nicolas Lapalu ◽  
Juliette Linglin ◽  
Isabelle Fudal ◽  
...  
Keyword(s):  
Host Plant ◽  
Large Scale ◽  
Field Experiments ◽  
Plant Residues ◽  
Plant Infection ◽  
Effector Genes ◽  
Controlled Conditions ◽  
Niche Adaptation ◽  
Depth Analysis ◽  
Fungal Genes

Abstract Background The fungus Leptosphaeria maculans has an exceptionally long and complex relationship with its host plant, Brassica napus, during which it switches between different lifestyles, including asymptomatic, biotrophic, necrotrophic, and saprotrophic stages. The fungus is also exemplary of “two-speed” genome organisms in the genome of which gene-rich and repeat-rich regions alternate. Except for a few stages of plant infection under controlled conditions, nothing is known about the genes mobilized by the fungus throughout its life cycle, which may last several years in the field. Results We performed RNA-seq on samples corresponding to all stages of the interaction of L. maculans with its host plant, either alive or dead (stem residues after harvest) in controlled conditions or in field experiments under natural inoculum pressure, over periods of time ranging from a few days to months or years. A total of 102 biological samples corresponding to 37 sets of conditions were analyzed. We show here that about 9% of the genes of this fungus are highly expressed during its interactions with its host plant. These genes are distributed into eight well-defined expression clusters, corresponding to specific infection lifestyles or to tissue-specific genes. All expression clusters are enriched in effector genes, and one cluster is specific to the saprophytic lifestyle on plant residues. One cluster, including genes known to be involved in the first phase of asymptomatic fungal growth in leaves, is re-used at each asymptomatic growth stage, regardless of the type of organ infected. The expression of the genes of this cluster is repeatedly turned on and off during infection. Whatever their expression profile, the genes of these clusters are enriched in heterochromatin regions associated with H3K9me3 or H3K27me3 repressive marks. These findings provide support for the hypothesis that part of the fungal genes involved in niche adaptation is located in heterochromatic regions of the genome, conferring an extreme plasticity of expression. Conclusion This work opens up new avenues for plant disease control, by identifying stage-specific effectors that could be used as targets for the identification of novel durable disease resistance genes, or for the in-depth analysis of chromatin remodeling during plant infection, which could be manipulated to interfere with the global expression of effector genes at crucial stages of plant infection.

Effects of moisture supply in the dry season and subsequent defoliation on persistence of the savanna grasses Themeda triandra, Heteropogon contortus and Panicum maximum

1992 ◽  
Vol 43 (2) ◽  
pp. 241 ◽  
Author(s):  
JJ Mott ◽  
MM Ludlow ◽  
JH Richards ◽  
AD Parsons
Keyword(s):  
Growing Season ◽  
Close Correlation ◽  
Dry Season ◽  
Carbon Gain ◽  
Panicum Maximum ◽  
Wet Season ◽  
Themeda Triandra ◽  
Heteropogon Contortus ◽  
Moisture Conditions ◽  
Sheath Material

The close correlation between grazing-induced mortality and major climatic patterns in Australian savannas, led us to the hypothesis that moisture conditions during the dry, non-growing season could affect sensitivity to grazing in the subsequent growing season. Using three widespread savanna species (Themeda triandra, Heteropogon contortus and Panicum maximum), this hypothesis was tested experimentally and the mechanisms controlling this response examined and quantified. In T. triandra drought during the dry season led to major mortality in defoliated plants in the next growing season. This mortality was caused by a synchrony of tillering at the commencement of the wet season, leaving few buds for replacement once parent tillers were killed by defoliation. T. triandra was also the most sensitive species to defoliation. This sensitivity was due to the poor ability of the plant to maintain positive carbon gain after defoliation. Several factors contributed to this poor ability, including: low total photosynthetic rate, low specific leaf area, and a large proportion of sheath material with poor photosynthetic capacity remaining after cutting. Both H. contortus and P. maximum growing under irrigated and fertilized conditions did not display any effects of previous moisture treatments when defoliated during the next wet season and were much less sensitive to defoliation than T. triandra.

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