Combined Influence of Grafting and Type of Protected Environment Structure on Agronomic and Physiological Traits of Single- and Cluster-Fruit-Bearing Cucumber Hybrids

Protected vegetable cultivation is a fast-growing sector in which grafting plays a crucial role for success. Cucumber is predominantly grown under protected conditions. The popular slicing (mini) cucumber comprises two segments, single- and cluster-fruit-bearing. In the present study, the performance of select fruit-bearing hybrids grafted as scions onto commercial Cucurbita hybrid rootstock ‘NS-55’ was evaluated under three different low-cost protected structures in arid regions. With respect to type of protected structure, cucumber performance was superior under a naturally ventilated polyhouse (NVP) than an insect net house (INH) or a shade net house (SNH). Micro-climate parameters inside NVP (air temperature, RH and PAR) were more congenial for cucumber than those in net houses, thereby facilitating improved physiology (chlorophyll fluorescence, chlorophyll and plant water potential) and leaf mineral status. Grafting invariably improved growth and yield parameters under all protected structures. Overall plant performance was better in the grafted cluster-fruit-bearing hybrid ‘Terminator’ than the single-fruit-bearing hybrid ‘Nefer’ or their non-grafted counterparts. Furthermore, NVP was found to be superior to net houses for water productivity, and grafted plants were more water use efficient than their counterpart non-grafted plants. Thus, NVP can be considered a suitable low-cost protected structure in conjunction with grafting to boost cucumber crop and water productivity in arid regions.

Dynamic aspects of plant water potential revealed by a microtensiometer

Water potential is a fundamental thermodynamic parameter that describes the activity of water. In this paper, we describe the continuous measurement of plant water potential, a reliable indicator of its water status, using a novel in situ sensor known as a microtensiometer in mature grapevines under field conditions. The microtensiometer operates on the principle of equilibration of water potentials of internal liquid water with an external vapour or liquid phase. We characterised the seasonal and diurnal dynamics of trunk water potentials (Ψtrunk) obtained from microtensiometers installed in two grapevine cultivars, Shiraz and Cabernet Sauvignon, and compared these values to pressure chamber-derived stem (Ψstem) and leaf (Ψleaf) water potentials as well as leaf stomatal conductance. Diurnal patterns of Ψtrunk matched those of Ψstem and Ψleaf under low vapour pressure deficit (VPD) conditions, but diverged under high VPD conditions. The highest diurnal values of Ψtrunk were observed shortly after dawn, while the lowest values were typically observed in the late afternoon. Differential responses of Ψtrunk to VPD were observed between cultivars, with Shiraz more sensitive than Cabernet to increasing VPD over long time scales, and both cultivars had a stronger VPD response than soil moisture response. On a diurnal basis, however, time cross correlation analysis revealed that Shiraz Ψtrunk lagged Cabernet Ψtrunk in response to changing VPD. Microtensiometers were shown to operate reliably under field conditions over several months. To be useful for irrigation scheduling of woody crops, new thresholds of Ψtrunk need to be developed.

L-band vegetation optical depth as an indicator of plant water potential in a temperate deciduous forest stand

<p>Vegetation optical depth (VOD) retrieved from microwave radiometry correlates with the total amount of water in vegetation. In addition to depending on overall biomass, the total amount of water in vegetation varies with relative water content, which is monotonically related to plant water potential, a quantity that drives plant hydraulic behavior. Thus there is a possible relationship between VOD and plant water potential. Previous studies have found evidence for that relationship on the scale of satellite pixels tens of kilometers across, but these comparisons suffer from significant scaling error. Here we used small-scale remote sensing to test the link between remotely sensed VOD and plant water potential. We placed an L-band radiometer on a tower above the canopy looking down at red oak forest stand during the 2019 growing season in the northeastern United States. We retrieved VOD with a single-channel algorithm based on continuous radiometer measurements and in-situ soil moisture data. We also measured water potentials of stem xylem and leaves on trees within the stand.</p><p>VOD exhibited a diurnal cycle similar to that of leaf and stem water potential, with a peak at approximately 5 AM. Over the whole growing season, VOD was also positively correlated with both the water potential of stem xylem and the xylem's dielectric constant (a proxy for water content). The presence of moisture on the leaves did not affect the observed relationship between VOD and xylem dielectric constant. We used our observed VOD-water potential relationship to estimate stand-level values for a radiative transfer parameter and a plant hydraulic parameter, which compared well with the published literature. Our findings support the use of VOD for plant hydraulic studies in temperate forests.</p>

L-band vegetation optical depth as an indicator of plant water potential in a temperate deciduous forest stand

Vegetation optical depth (VOD) retrieved from microwave radiometry correlates with the total amount of water in vegetation, based on theoretical and empirical evidence. Because the total amount of water in vegetation varies with relative water content (as well as with biomass), this correlation further suggests a possible relationship between VOD and plant water potential, a quantity that drives plant hydraulic behavior. Previous studies have found evidence for that relationship on the scale of satellite pixels tens of kilometers across, but these comparisons suffer from significant scaling error. Here we used small-scale remote sensing to test the link between remotely sensed VOD and plant water potential. We placed an L-band radiometer on a tower above the canopy looking down at red oak forest stand during the 2019 growing season in central Massachusetts, United States. We measured stem xylem and leaf water potentials of trees within the stand and retrieved VOD with a single-channel algorithm based on continuous radiometer measurements and measured soil moisture. VOD exhibited a diurnal cycle similar to that of leaf and stem water potential, with a peak at approximately 05:00 eastern daylight time (UTC−4). VOD was also positively correlated with both the measured dielectric constant and water potentials of stem xylem over the growing season. The presence of moisture on the leaves did not affect the observed relationship between VOD and stem water potential. We used our observed VOD–water-potential relationship to estimate stand-level values for a radiative transfer parameter and a plant hydraulic parameter, which compared well with the published literature. Our findings support the use of VOD for plant hydraulic studies in temperate forests.

The Impacts of Drought Stress and Phytophthora cinnamomi Infection on Short-Term Water Relations in Two Year-Old Eucalyptus obliqua

The effects of drought stress, Phytophthora cinnamomi infection and their interaction on water relations and growth were examined for 28 days on two year-old potted trees of Eucalyptus obliqua (L’Hér.). There were significant effects of drought stress on plant photosynthesis, stomatal conductance, biomass accumulation, plant water potential at turgor loss point and the bulk modulus of elasticity. E. obliqua was successfully infected but the trees showed only mild symptoms. Infection with P. cinnamomi led to a significant reduction in the root biomass and root-to-shoot ratio in well-watered and droughted plants but did not impact water relations. There was no observable cumulative effect of drought and P. cinnamomi infection. There are multiple potential reasons why P. cinnamomi infection did not lead to drought-like symptoms in E. obliqua, including short experimental duration, delayed infection symptoms, potential resistance of E. obliqua and a possible lower aggressiveness of the P. cinnamomi strain. Hence, our results indicate that P. cinnamomi infection will not always lead to immediate short-term symptoms, and that plants that are mildly symptomatic respond very similar to drought stress compared to non-infected trees.

Effect of hail net on the water potential of an apple orchard

Apple production has seen a decline in yields in recent years, primarily due to ecological factors such as drought, water stress, water scarcity, uneven rainfall distribution, frost damage and hail damage. Ecological factors that are harmful to the plant can be eliminated by human intervention, irrigation or the use of hail net. In our study, we investigated the positive effects of hail net on the development of plant water potential as the vegetation progressed, in non-irrigation area with temperature and humidity. Water potential values were determined using a field osmometer. Confirmed the positive effect of the ice protection net in the apple orchard of Early Gold and Golden Reinders. Our results were supported by statistical analyzes our results.

L-band vegetation optical depth as an indicator of plant water potential in a temperate deciduous forest stand

Vegetation optical depth (VOD) retrieved from microwave radiometry correlates with the total amount of water in vegetation, based on theoretical and empirical evidence. Because the total amount of water in vegetation varies with relative water content (as well as with biomass), this correlation further suggests a possible relationship between VOD and plant water potential, a quantity that drives plant hydraulic behavior. Previous studies have found evidence for that relationship on the scale of satellite pixels tens of kilometers across, but these comparisons suffer from significant scaling error. Here we used small-scale remote sensing to test the link between remotely sensed VOD and plant water potential. We placed an L-band radiometer on a tower above the canopy looking down at red oak forest stand during the 2019 growing season in central Massachusetts, United States. We measured stem xylem and leaf water potentials of trees within the stand, and retrieved VOD with a single-channel algorithm based on continuous radiometer measurements and measured soil moisture. VOD exhibited a diurnal cycle similar to that of leaf and stem water potential, with a peak at approximately 5 AM. VOD was also positively correlated with both the measured dielectric constant and water potentials of stem xylem over the growing season. The presence of moisture on the leaves did not affect the observed relationship between VOD and stem water potential. We used our observed VOD-water potential relationship to estimate stand-level values for a radiative transfer parameter and a plant hydraulic parameter, which compared well with the published literature. Our findings support the use of VOD for plant hydraulic studies in temperate forests.