Maize lateral root developmental plasticity induced by mild water stress. I: Genotypic variation across a high‐resolution series of water potentials

The effect of water stress during summer and recovery after rain on herbage accumulation, leaf growth components, stomatal conductance and leaf water relations of white clover (Trifolium repens cv. Haifa) and phalaris (Phalaris aquatica cv. Australian Commercial) was studied in an established mixed pasture under dryland (dry) or irrigated (wet) conditions. Soil water deficits under dry conditions reached 150 mm and soil water potentials in the top 20 cm declined to nearly -2 MPa after 50 days of dry weather. Water stress severely restricted growth of both species but then after rain fell, white clover growth rates exceeded those of phalaris. Under irrigation, white clover produced twice the herbage mass of phalaris but under dry conditions herbage production was similar from both species. Leaf appearance rates per tiller or stolon were slightly higher for white clover than phalaris but were reduced by 20% under water stress in both species. Leaf or petiole extension rates were more sensitive to water stress than leaf appearance rates and declined by 75% in phalaris and 90% in white clover. The ratio of leaf or petiole extension rates on dry/wet treatments was similar for both species in relation to leaf relative water contents, but in relation to leaf water potentials phalaris maintained higher leaf growth rates. Phalaris maintained a higher leaf relative water content in relation to leaf water potentials than did white clover and also maintained higher leaf water potentials in relation to the soil water potential in the top 20 cm. Stomata1 conductances for both species declined by 80-90% with increasing water stress, and both species showed similar stomatal responses to bulk leaf water potentials and leaf relative water contents. It is suggested that the poorer performance of white clover under water stress may be due principally to a shallower root system than phalaris and not due to any underlying major physiological differences. The white clover cultivar used in this study came from the mediterranean region and showed some different responses to water stress than previously published evidence on white clover. This suggests genetic variation in responses to water stress may exist within white clover. To maintain white clover in a pasture under dry conditions it is suggested that grazing practices aim to retain a high proportion of growing points.

Download Full-text

Photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress

Acta Amazonica ◽

10.1590/s0044-59672014000100007 ◽

2014 ◽

Vol 44 (1) ◽

pp. 67-77 ◽

Cited By ~ 2

Author(s):

Gracilene Fernandes da Costa Azevedo

Keyword(s):

Water Stress ◽

Higher Plants ◽

Field Capacity ◽

Outdoor Exposure ◽

Photosynthetic Parameters ◽

Bertholletia Excelsa ◽

Full Sunlight ◽

Carapa Guianensis ◽

Light Levels ◽

Mild Water Stress

Light and water are important factors that may limit the growth and development of higher plants. The aim of this study was to evaluate photosynthetic parameters and growth in seedlings of Bertholletia excelsa and Carapa guianensis in response to pre-acclimation to full sunlight and mild water stress. I used six independent pre-acclimation treatments (0, 90 (11h15-12h45), 180 (10h30-13h30), 360 (09h00-15h00), 540 (07h30-16h30) and 720 min (06h00-18h00)) varying the time of exposure to full sunlight (PFS) during 30 days, followed by whole-day outdoor exposure for 120 days. Before PFS, the plants were kept in a greenhouse at low light levels (0.8 mol m-2 day-1). The PFS of 0 min corresponded to plants constantly kept under greenhouse conditions. From the beginning to the end of the experiment, each PFS treatment was submitted to two water regimes: moderate water stress (MWS, pre-dawn leaf water potential (ΨL) of -500 to -700 kPa) and without water stress (WWS, ΨL of -300 kPa, soil kept at field capacity). Plants under MWS received only a fraction of the amount of water applied to the well-watered ones. At the end of the 120-day-period under outdoor conditions, I evaluated light saturated photosynthesis (Amax), stomatal conductance (g s), transpiration (E) and plant growth. Both Amax and g s were higher for all plants under the PFS treatment. Stem diameter growth rate and Amax were higher for C. guianensis subjected to MWS than in well-watered plants. The contrary was true for B. excelsa. The growth of seedlings was enhanced by exposure to full sunlight for 180 minutes in both species. However, plants of B. excelsa were sensitive to moderate water stress. The higher photosynthetic rates and faster growth of C. guianensis under full sun and moderate water stress make this species a promissory candidate to be tested in reforestation programs.

Download Full-text

Morphological Features and Biomass Partitioning of Lucerne Plants (Medicago sativa L.) Subjected to Water Stress

Agronomy ◽

10.3390/agronomy10030322 ◽

2020 ◽

Vol 10 (3) ◽

pp. 322

Author(s):

Yong-Zhong Luo ◽

Guang Li ◽

Guijun Yan ◽

Hui Liu ◽

Neil C. Turner

Keyword(s):

Water Stress ◽

Water Supply ◽

Lateral Root ◽

Dry Weight ◽

Agricultural Systems ◽

Root Dry Weight ◽

Severe Water Stress ◽

Medicago Sativa L ◽

Leaf Dry Weight ◽

Semi Arid

Drought is one of the major abiotic stresses affecting the morphological, physiological, and metabolic processes of plants, and hence their growth and production on a global scale. Lucerne (Medicago sativa L.) is one of the most popular pasture species in semi-arid regions and plays a critical role in sustaining agricultural systems in many areas of the world. In order to evaluate the effect of water deficits on the growth and biomass distribution in different tissues of lucerne, plant height, leaf dry weight, leaf number and area, root dry weight, taproot length and lateral root number, and stem dry weight were measured at four stages from the seedling to flowering stages under three water regimes: (i) adequate water supply (minimum soil water content 85% pot capacity (PC)), (ii) moderate water stress (65% PC), and (iii) severe water stress (45% PC), imposed under a rainout shelter. With limited water supply, plant height, leaf number, leaf area and dry weight, taproot length, and total biomass were reduced, while lateral root numbers increased. The number of smaller leaves and root dry weight increased under moderate water stress, whereas severe water stress reduced them. Leaf, stem, and total dry weight were all reduced by the water deficits, but leaf dry weight was reduced the most and root dry weight the least, so there was a redistribution of biomass towards the roots, increasing the root–shoot ratio. These results help us to understand the response of lucerce to water stress and assist in developing a foundation for the sustainable use of lucerne in semi-arid agricultural systems.

Download Full-text

Development in Cowpea (Vigna unguiculata). I. The Influence of Temperature on Seed Germination and Seedling Emergence

Experimental Agriculture ◽

10.1017/s0014479700025801 ◽

1996 ◽

Vol 32 (1) ◽

pp. 1-12 ◽

Cited By ~ 21

Author(s):

P. Q. Craufurd ◽

R. H. Ellis ◽

R. R. J. Summerfield ◽

L. Menin

Keyword(s):

Seed Germination ◽

Vigna Unguiculata ◽

Developmental Plasticity ◽

Seedling Emergence ◽

Genotypic Variation ◽

Thermal Time ◽

Influence Of Temperature ◽

Influence Of Temperature On ◽

Semi Arid

SUMMARYThe base (Tb), optimum (To) and ceiling (Tce) temperature for 50% seed germination and seedling emergence, and the thermal time at sub-optimal temperatures (θ1), were examined in experiments with a range of cowpea genotypes from different habitats and latitudes. There was substantial genotypic variation in seed germination for Tb and To, but not for Tce. There was no evidence that genotypes from semi-arid habitats had higher values of To or Tce, but estimates of Tb for seed germination were related to latitude and were highest in genotypes originating from close to the equator. The significance of these responses as a component of developmental plasticity in relation to the adaptation of cowpeas is discussed.

Download Full-text

Genotypic Variation in Wheat in Response to Water Stress and Abscisic Acid-Induced Accumulation of Osmolytes in Developing Grains

Journal of Agronomy and Crop Science ◽

10.1046/j.0931-2250.2003.00072.x ◽

2004 ◽

Vol 190 (1) ◽

pp. 39-45 ◽

Cited By ~ 37

Author(s):

H. Nayyar ◽

D. P. Walia

Keyword(s):

Abscisic Acid ◽

Water Stress ◽

Genotypic Variation ◽

Response To Water ◽

Developing Grains

Download Full-text

Making the invisible visible: using UAS-based high-resolution color-infrared imagery to identify buried medieval monastery walls

Journal of Unmanned Vehicle Systems ◽

10.1139/juvs-2014-0017 ◽

2015 ◽

Vol 3 (2) ◽

pp. 58-67 ◽

Cited By ~ 1

Author(s):

Jan Rudolf Karl Lehmann ◽

Keturah Zoe Smithson ◽

Torsten Prinz

Keyword(s):

Remote Sensing ◽

Water Stress ◽

High Resolution ◽

Vegetation Index ◽

Archaeological Site ◽

Unmanned Aerial Systems ◽

Surrounding Water ◽

Normalised Difference Vegetation Index ◽

Remote Sensing Techniques ◽

Aerial Systems

Remote sensing techniques have become an increasingly important tool for surveying archaeological sites. However, budgeting issues in archaeological research often limit the application of satellite or airborne imagery. Unmanned aerial systems (UAS) provide a flexible, quick, and more economical alternative to commonly used remote sensing techniques. In this study, the buried features of the archaeological site of the Kleinburlo monastery, near Münster, Germany, were identified using high-resolution color–infrared (CIR) images collected from a UAS platform. Based on these CIR images, a modified normalised difference vegetation index (NDVIblue) was calculated, showing reflectance spectra of vegetation anomalies caused by water stress. In the presented study, the vegetation growing on top of the buried walls was better nourished than the surrounding plants because very wet conditions over the days previous to data collection caused higher levels of water stress in the surrounding water-drenched land. This difference in water stress was a good indicator for detecting archaeological remains.

Download Full-text

Mapping Maize Water Stress Based on UAV Multispectral Remote Sensing

Remote Sensing ◽

10.3390/rs11060605 ◽

2019 ◽

Vol 11 (6) ◽

pp. 605 ◽

Cited By ~ 14

Author(s):

Liyuan Zhang ◽

Huihui Zhang ◽

Yaxiao Niu ◽

Wenting Han

Keyword(s):

Water Stress ◽

High Resolution ◽

Relative Humidity ◽

Air Temperature ◽

Vegetation Index ◽

Multispectral Imagery ◽

Crop Water ◽

Significant Difference ◽

Maturation Stages ◽

Crop Water Stress

Mapping maize water stress status and monitoring its spatial variability at a farm scale are a prerequisite for precision irrigation. High-resolution multispectral images acquired from an unmanned aerial vehicle (UAV) were used to evaluate the applicability of the data in mapping water stress status of maize under different levels of deficit irrigation at the late vegetative, reproductive and maturation growth stages. Canopy temperature, field air temperature and relative humidity obtained by a handheld infrared thermometer and a portable air temperature/relative humidity meter were used to establish a crop water stress index (CWSI) empirical model under the weather conditions in Ordos, Inner Mongolia, China. Nine vegetation indices (VIs) related to crop water stress were derived from the UAV multispectral imagery and used to establish CWSI inversion models. The results showed that non-water-stressed baseline had significant difference in the reproductive and maturation stages with an increase of 2.1 °C, however, the non-transpiring baseline did not change significantly with an increase of 0.1 °C. The ratio of transformed chlorophyll absorption in reflectance index (TCARI) and renormalized difference vegetation index (RDVI), and the TCARI and soil-adjusted vegetation index (SAVI) had the best correlations with CWSI. R2 values were 0.47 and 0.50 for TCARI/RDVI and TCARI/SAVI at the reproductive and maturation stages, respectively; and 0.81 and 0.80 for TCARI/RDVI and TCARI/SAVI at the late reproductive and maturation stages, respectively. Compared to CWSI calculated by on-site measurements, CWSI values retrieved by VI-CWSI regression models established in this study had more abilities to assess the field variability of crop and soil. This study demonstrates the potentiality of using high-resolution UAV multispectral imagery to map maize water stress.

Download Full-text