scholarly journals Estimating Vertical Distribution of Leaf Water Content within Wheat Canopies after Head Emergence

2021 ◽  
Vol 13 (20) ◽  
pp. 4125
Author(s):  
Weiping Kong ◽  
Wenjiang Huang ◽  
Lingling Ma ◽  
Lingli Tang ◽  
Chuanrong Li ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Water Content ◽  
Near Infrared ◽  
Field Experiments ◽  
Estimation Method ◽  
Middle Layer ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Growth Stages ◽  
Spectral Indices

Monitoring vertical profile of leaf water content (LWC) within wheat canopies after head emergence is vital significant for increasing crop yield. However, the estimation of vertical distribution of LWC from remote sensing data is still challenging due to the effects of wheat spikes and the efficacy of sensor measurement from the nadir direction. Using two-year field experiments with different growth stages after head emergence, N rates, wheat cultivars, we investigated the vertical distribution of LWC within canopies, the changes of canopy reflectance after spikes removal, the relationship between spectral indices and LWC in the upper-, middle- and bottom-layer. The interrelationship among vertical LWC were constructed, and four ratio of reflectance difference (RRD) type of indices were proposed based on the published WI and NDWSI indices to determine vertical distribution of LWC. The results indicated a bell shape distribution of LWC in wheat plants with the highest value appeared at the middle layer, and significant linear correlations between middle-LWC vs. upper-LWC and middle-LWC vs. bottom-LWC (r ≥ 0.92) were identified. The effects of wheat spikes on spectral reflectance mainly occurred in near infrared to shortwave infrared regions, which then decreased the accuracy of LWC estimation. Spectral indices at the middle layer outperformed the other two layers in LWC assessment and were less susceptible to wheat spikes effects, in particular, the newly proposed narrow-band WI-4 and NDWSI-4 indices exhibited great potential in tracking the changes of middle-LWC (R2 = 0.82 and 0.84, respectively). By taking into account the effects of wheat spikes and the interrelationship of vertical LWC within canopies, an indirect induction strategy was developed for modeling the upper-LWC and bottom-LWC. It was found that the indirect induction models based on the WI-4 and NDWSI-4 indices were more effective than the models obtained from conventional direct estimation method, with R2 of 0.78 and 0.81 for the upper-LWC estimation, and 0.75 and 0.74 for the bottom-LWC estimation, respectively.

Spectral assessments of wheat plants grown in pots and containers under saline conditions

2013 ◽  
Vol 40 (4) ◽  
pp. 409 ◽  
Author(s):  
Harald Hackl ◽  
Bodo Mistele ◽  
Yuncai Hu ◽  
Urs Schmidhalter
Keyword(s):  
Water Potential ◽  
Water Content ◽  
Aboveground Biomass ◽  
Leaf Water ◽  
Leaf Water Content ◽  
Spectral Indices ◽  
Fresh Weight ◽  
Normalised Difference Vegetation Index ◽  
Spectral Sensing ◽  
Reflectance Ratio

Spectral measurements allow fast nondestructive assessment of plant traits under controlled greenhouse and close-to-field conditions. Field crop stands differ from pot-grown plants, which may affect the ability to assess stress-related traits by nondestructive high-throughput measurements. This study analysed the potential to detect salt stress-related traits of spring wheat (Triticum aestivum L.) cultivars grown in pots or in a close-to-field container platform. In two experiments, selected spectral indices assessed by active and passive spectral sensing were related to the fresh weight of the aboveground biomass, the water content of the aboveground biomass, the leaf water potential and the relative leaf water content of two cultivars with different salt tolerance. The traits were better ascertained by spectral sensing of container-grown plants compared with pot-grown plants. This may be due to a decreased match between the sensors’ footprint and the plant area of the pot-grown plants, which was further characterised by enhanced senescence of lower leaves. The reflectance ratio R760 : R670, the normalised difference vegetation index and the reflectance ratio R780 : R550 spectral indices were the best indices and were significantly related to the fresh weight, the water content of the aboveground biomass and the water potential of the youngest fully developed leaf. Passive sensors delivered similar relationships to active sensors. Across all treatments, both cultivars were successfully differentiated using either destructively or nondestructively assessed parameters. Although spectral sensors provide fast and qualitatively good assessments of the traits of salt-stressed plants, further research is required to describe the potential and limitations of spectral sensing.

Mapping of Leaf Water Content Using Near-Infrared Hyperspectral Imaging

2013 ◽  
Vol 67 (11) ◽  
pp. 1302-1307 ◽  
Author(s):  
Sakura Higa ◽  
Hikaru Kobori ◽  
Satoru Tsuchikawa
Keyword(s):  
Water Content ◽  
Hyperspectral Imaging ◽  
Near Infrared ◽  
Leaf Water ◽  
Leaf Water Content

scholarly journals Critical Leaf Water Content for Maize Photosynthesis under Drought Stress and Its Response to Rewatering

2021 ◽  
Vol 13 (13) ◽  
pp. 7218
Author(s):  
Xingyang Song ◽  
Guangsheng Zhou ◽  
Qijin He
Keyword(s):  
Drought Stress ◽  
Water Content ◽  
Global Climate ◽  
Leaf Water ◽  
Extreme Weather Events ◽  
Leaf Water Content ◽  
Growth Stages ◽  
Stomatal Limitation ◽  
Jointing Stage ◽  
Maize Photosynthesis

Crop photosynthesis is closely related to leaf water content (LWC), and clarifying the LWC conditions at critical points in crop photosynthesis has great theoretical and practical value for accurately monitoring drought and providing early drought warnings. This experiment was conducted to study the response of LWC to drought and rewatering and to determine the LWC at which maize photosynthesis reaches a maximum and minimum and thus changes from a state of stomatal limitation (SL) to non-stomatal limitation (NSL). The effects of rehydration were different after different levels of drought stress intensity at different growth stages, and the maize LWC recovered after rewatering following different drought stresses at the jointing stage; however, the maize LWC recovered more slowly after rewatering following 43 days and 36 days of drought stress at the tasselling and silking stages, respectively. The LWC when maize photosynthesis changed from SL to NSL was 75.4% ± 0.38%, implying that the maize became rehydrated under physiologically impaired conditions. The LWCs at which the maize Vcmax25 reached maximum values and zero differed between the drought and rewatering periods. After exposure to drought stress, the maize exhibited enhanced drought stress tolerance, an obviously reduced suitable water range, and significantly weakened photosynthetic capacity. These results provide profound insight into the turning points in maize photosynthesis and their responses to drought and rewatering. They may also help to improve crop water management, which will be useful in coping with the increased frequency of drought and extreme weather events expected under global climate change.

Various responses of sunflower genotypes to water stress on newly reclaimed sandy soil

2013 ◽  
Vol 61 (1) ◽  
pp. 55-69
Author(s):  
A. Salem ◽  
A. Omar ◽  
M. Ali
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Transpiration Rate ◽  
Leaf Water ◽  
Oil Yield ◽  
Leaf Water Content ◽  
Growth Stages ◽  
Severe Drought ◽  
Water Supplies ◽  
Water Regimes

Water stress is a severe limitation for crop growth especially in arid and semi-arid regions of the world, as it has a vital role in plant growth and development at all growth stages. The aim of the present study was to evaluate the differential responses of twelve sunflower genotypes to three levels of water supply and select the most suitable one for such conditions. Two field experiments were conducted under adequate (7140 m3/ha), moderate (4760 m3/ha) and severe (2380 m3/ha) water regimes to evaluate the chlorophyll index, transpiration rate, leaf water content, plant height, head diameter, seeds/head, 1000-seed weight, seed and oil yield of the genotypes. Moderate and severe levels of drought had a significant impact on the transpiration rate, leaf water content, yield-contributing characters and oil yield of all the sunflower genotypes. However, the sunflower genotypes showed different responses to the different water regimes. The highest seed and oil yields were attained in L990 and Giza 102 in the case of adequate water supplies, while L38 was the best under moderate and severe drought conditions. On the basis of the results, sunflower genotype L990 could be recommended for growing when adequate water supplies are available, and L38 under moderate and severe water regimes to obtain high seed and oil yields.

scholarly journals Leaf water content estimation using top-of-canopy airborne hyperspectral data

2021 ◽  
Vol 102 ◽  
pp. 102393
Author(s):  
Rahul Raj ◽  
Jeffrey P. Walker ◽  
Vishal Vinod ◽  
Rohit Pingale ◽  
Balaji Naik ◽  
...  
Keyword(s):  
Water Content ◽  
Hyperspectral Data ◽  
Leaf Water ◽  
Leaf Water Content
Sign in / Sign up

Export Citation Format

Share Document