Water Potential

Three different drought stress levels (water potential of the nutrient solution, Ψs=− 0.6,− 1.2 and− 1.8 MPa, respectively), and a control treatment (Ψs=− 0.1 MPa), were applied during 2 weeks to three almond species, followed by 3 weeks of recovery. The selected test species were Prunus dulcis (Miller) D. Webb (bitter almond) and two wild almond species, P. lycioides (Spach) CK Schneider and P. scoparia (Spach) CK Schneider. All three are species native to Iran, and can be used as rootstock, but only P. dulcis is actually used for ...

• Alterations in plant chemistry underpin a suite of physiological adaptations to arid conditions. Qualitative and quantitative differences in leaf chemistry are found in the genus Eucalyptus correlating with physiological adaptation to aridity. ... • Here we investigate seasonal ...

Agave tequilana stem explants were used to produce adventitious shoots under a set of different water potentials induced by different concentrations of gelrite in the medium. At high water potentials all shoots were vitrified; as the medium water potential became more negative the degree of vitrification decreased but the number of shoots per explant also diminished. The enzymes NADH and NAD-GDH (EC. 1.4. 1.2) were measured along the water potential gradient. GDH activity was high in the non-vitrified tissues and decreased ...

Photinia plants produced in 11.4-liter polyethylene containers using a pine bark-based medium were transplanted into a well-drained sand and irrigated on alternate days. Polyethylene barriers were placed under half the root balls at transplanting to limit gravitational water loss. Plant water potential was measured diurnally between irrigations, and root growth was determined at 4-month intervals. Plants with barriers averaged higher cumulative daily water stress than control plants over the year, although predawn and minimum water potentials were similar. Growth index and trunk diameter were similar for the plants over barriers and controls, but the former were taller after 1 year. Plants with barriers had twice the horizontal root growth into the landscape site as control plants, resulting in twice the root mass in the landscape after 1 year.

Most maize (Zea mays L.) in México is cultivated under rainfed conditions with a high frequency of drought stress periods during silking, a stage which is very sensitive to water deficits. Since the effect of drought depends on the genotype, in this study we compared four maize lines (L6, L13, L14 and L16), which had previously shown contrasting responses to osmotic stress in vitro. Two water regimes were imposed: watering (every 10 d) and drought stress (without irrigation from 48-97 d after planting). Variables measured were grain yield, soil moisture, hydric potential and their components in leaves and female inflorescence, photosynthetic rate, aboveground biomass, days to flowering, and leaf and young ear concentration of soluble sugars. Yield data were used to calculate the drought susceptibility index (DSI). Based on yield and DSI, L14 and L16 behaved as tolerant lines to drought stress, while lines L6 and L13 were susceptible. Tolerant lines showed lower reductions in kernel ...

The environmental requirements leading to germination were determined by three common species found during
the June-October 2009 rainy season in a peri-urban site from Morelia, Michoacán, Mexico, where the construction of
a campus of the Universidad Nacional Autónoma de México (UNAM) was underway. In particular, we evaluated
responses in the laboratory to low-temperature stratification, day/night air temperature, and water potential for the
native Onagraceae Lopezia racemosa and Ludwigia octovalvis, and the exotic Rumex crispus. Low-temperature stratification
had no effect on germination by Polygonaceae L. racemosa, for which maximum germination averaging 88% was
optimal at 25/15 and 30/20 C. Germination at 21 d was halved at –0.5 MPa and completely inhibited at –1.0 MPa.
The seeds of L. octovalvis were also insensitive to low temperature stratification and their germination never exceeded
70%, with the two highest temperatures of 30/20 and 35/25 C being the optimum. For this species germination was
maximal at 0.0 MPa, decreasing significantly under every treatment with a minimum germination of 21% for seeds
incubated at –0.1 MPa. Germination for the exotic R. crispus was delayed by low-temperature stratification, although
all its seeds germinated regardless of the temperature or water potential treatment. While the environmental requirements
for germination of ephemeral species often match the typical climate of their growing season, the differential
responses found for the species considered in the present study provide some insight into the mechanisms leading to
changes in species composition for communities from disturbed environments, including the displacement of native
species and the proliferation of exotic, potentially invasive plants.