Moderate Moisture Stress Research Articles

Exogenous Salicylic Acid Induced Drought Stress Tolerance in Immature Tea (<em>Camellia sinensis</em> L.) Plants

Salicylic acid (SA) has been known to induce drought tolerance in many plant species. In this study, we investigated the potential of exogenous application of SA to enhance drought tolerance in immature tea plants under glasshouse conditions at the Tea Research Institute in Talawakelle, Sri Lanka. One-year-old potted tea cultivars known for drought tolerance were used in the study. The plants were subjected to a drying cycle while being foliar sprayed with different concentrations of SA along with well-watered (WW), water-spray (WS) and no-spray (NS) treatments. Data were collected at 18 hours, 14 days after spraying (DAS), 21 DAS, and during the recovery after re-watering at 21 DAS. Based on the results obtained from the glasshouse study, the effective concentration of 150 mg L-1 SA was selected for further testing under field conditions in Talawakelle using three-year-old tea plants. The field experiment followed a randomized complete block design (RCBD) with three blocks. When the plants reached a moderate moisture stress level, they were foliar-sprayed with 150 mg L-1 SA, WS and NS treatments were included as controls. Data were collected at 7 DAS, 14 DAS, 21 DAS, and during the recovery phase after rain. The results showed that drought stress led to a decline in gas exchange parameters, relative water content, and an increase in the accumulation of osmolytes. However, the exogenous application of 150 mg L-1 SA significantly improved physiological processes such as gas exchange, osmolyte accumulation, and antioxidant activity, thus effectively enhancing drought tolerance in immature tea plants.

Evaluation of remobilization rate, grain yield and antioxidant content of maize in reaction to biochar and humic acid amounts under water deficiency stress

In order to investigate the effect of biochar and humic acid on the rate of remobilization, grain yield and antioxidant content of maize under water deficiency stress, an experiment was conducted as asplit-split plot in the form of a randomized complete blocks design with three replications in Ahvaz, southwest of Iran. The main plot involved water stress with three irrigation levels after depleting 30, 40 and 50% of field capacity, non-stress, moderate stress, and severe stress, respectively, asubplot withbiochar with 2 control levels (no use of biochar) and application of 4 tons in biochar hectares and another subplot having humic acid with 4 control levels (no use of humic acid) and application of 2, 4 and 6 liters per hectare of humic acid. The results showed that the effect of water deficit stress, biochar and humic acid on grain yield, remobilization rate, current photosynthesis, share of current photosynthesis, catalase and superoxide dismutase enzymes was significant at the level of 1% probability. The highest grain yield was related to irrigation treatment after depleting 40% of field capacity and application of 4 tons per hectare of biochar. In total, the use of 4 liters per hectare of humic acid in moderate moisture stress conditions due to its positive role on the growth and hence on the 42% increase in the yield, compared to severe stress treatment and no consumption of humic acid, can be recommended under arid and semi-arid conditions to save water consumption, and reduce the effects of water deficit stress.

Effect of soil moisture stress at booting and flowering stages on pollen development, pollination and fertilization in upland NERICA cultivars

Spikelet sterility induced by soil moisture stress during reproductive development greatly limits grain yield in upland rice. This study aimed to elucidate differences in responses to soil moisture stress for pollen development, pollination and fertilization among upland rice cultivars. A greenhouse experiment with a split-plot design was performed for five different soil moisture treatments (T1 to T5) as the main plots and three cultivars (NERICA 1, NERICA 4 and Yumenohatamochi) as subplots, each with three replicates. Plants in pots were grown under well-watered condition (T1) and various moisture stress conditions: moderate at the booting stage (T2), severe at the booting stage (T3), moderate at the flowering stage (T4) or severe at the flowering stage (T5). During the 9-day stress period, soil moisture was maintained at -10 to -20 kPa for moderate moisture stress or -20 to -49 kPa for severe moisture stress under controlled irrigation. NERICA 1 had fewer differentiated microspores and developed pollen grains in T2 and T3 and showed poorer anther dehiscence and fewer pollen grains on the stigma than did NERICA 4 and Yumenohatamochi. NERICA 4 showed a lower percentage of basal dehiscence in T4 and T5, causing fewer pollen grains to be deposited on the stigma than for NERICA 1 and Yumenohatamochi. The results indicate that the highly sensitive process of fertilization are pollen development in NERICA 1 and pollination in NERICA 4 under soil moisture stress

Selection within Coffea arabica cv. Ruiru 11 for high cup quality

In recent years, consumer awareness about the quality of different coffees has increased and therefore production and supply of coffee with excellent quality attach more significance. As a result, many coffee producing countries include coffee quality assessment in their coffee variety development programmes. The present study was undertaken to evaluate the variation of cup quality traits and determine their associations with each other and with overall cup quality among the sibs of Coffea arabica L. cultivar Ruiru 11. In addition, the study targeted to select specific Ruiru 11 sibs with superior cup quality and wide adaptability based on assessment of 7 traits including fragrance, flavor, aftertaste, acidity, body, balance, preference and their total score. Thirty four full-sib families representing this hybrid cultivar grown in three different agro climatic zones of Kenya were used for the study. Rainfall amounts during various phases of berry development were used to explain the differences observed in the discriminating abilities of the locations for cup quality traits. The results showed that Ruiru 11 sibs were highly variable in all the cup quality traits except body. Site variations were also highly significant and the sibs were best differentiated in the sites where moderate moisture stress occurred during bean expansion and filling stages. Genotype by environment (G × E) interactions, were observed for all the traits except body. A highly significant positive correlation was registered between all traits. The study also demonstrated the existence of a high variation in cup quality among Ruiru 11 sibs. The most widely adapted Ruiru 11 sibs were identified to be R11-52, R11-117, R11-131, R11-107, R11-121, R11-11, R11-137 and R11-22. Key words: Arabica coffee, Ruiru 11 sibs, site variations, correlation coefficients, Kenya.

Morphology, Physiology, Survival, and Field Performance of Containerized Coastal Douglas Fir Seedlings Given Different Dormancy-induction Regimes

The effects of different dormancy-induction regimes on first-year containerized coastal Douglas fir [Pseudotsuga menziesii (Mirb.) Franco var. menziesii] seedling morphology and physiology in the nursery, as well as seedling survival and performance after one growing season in a common garden, were investigated. In early July, three dormancy-induction regimes were applied: moderate moisture stress (MS), short day (SD), and short day with moderate moisture stress (SD+MS). In early October, seedling height, root collar diameter, and shoot dry weight were unaffected by regime, but root dry weight was reduced in seedlings from the MS and SD+MS regimes compared with the SD regime. At this time, morphogenesis was completed in all terminal buds of seedlings from both SD regimes, whereas it continued in all terminal buds of seedlings from the MS regime. Furthermore, 25% to 88% of terminal buds from the SD regimes were endodormant, but none from the MS regime were endodormant. In March, budbreak occurred at the same time in seedlings from the two SD regimes and was earlier than in seedlings from the MS regime; root growth capacity was unaffected by regime. After one growing season, there were no regime differences in seedling survival, root collar diameter, shoot dry weight, root dry weight, length of the current-year leader, or number of needles on the leader.

High-throughput virus-induced gene-silencing approach to assess the functional relevance of a moisture stress-induced cDNA homologous to lea4

The abiotic stress-responsive cDNA database and their expression profiles suggest that stress genes are many and diverse. However, characterization and validation of their functional significance has been a constraint to assessing their role in imparting tolerance. Virus-induced gene silencing (VIGS) is a potential option for assessing the functional significance of stress genes. Here the effectiveness of VIGS to silence the expression of an ABA-responsive lea4 (late embryogenic abundant) gene involved in stress tolerance is documented. In the present study, low moisture-stress protocols were developed in such a way that the plants experienced the desired stress level when silencing the target stress gene using VIGS was at a maximum. The functional relevance of a groundnut (Arachis hypogaea) subtracted-stress cDNA clone putative lea4 was examined by VIGS in tomato. A 400 bp fragment of lea4 was cloned into tobacco rattle virus-based VIGS vector to trigger post-transcriptional gene silencing by Agrobacterium-mediated inoculation in tomato plants. In silenced plants only lea4 transcripts showed a substantial decline, whereas the expression of other known stress-responsive genes such as apx (ascorbate peroxidase) and elip (early light-induced protein) were unaltered. Under moderate moisture stress, the silenced plants showed enhanced susceptibility as measured by cell viability, superoxide radical activity, and cell osmotic adjustment. This approach illustrates the potential benefits of VIGS in identifying functional relevance of low moisture stress-responsive genes. It is also demonstrated that heterologous probes with a fairly high degree of homology to the native genes can be used to study the functional relevance of stress-responsive genes using VIGS.

Selection for bean and liquor qualities within related hybrids of Arabica coffee in multilocal field trials

Summary The success of a new variety of Arabica coffee (Coffea arabica L.) depends to an important extent on its liquor and bean qualities. Selection for these traits is however constrained by the prevalence of large genotype-by-environment (G×E) interactions in conjunction with the low genetic variability characteristic of this species. The aim of this study was to assess the extent to which key bean and liquor traits are affected by the environments and could be combined in order to improve the efficiency of selection for coffee quality in a narrow genetic basis set of hybrids obtained from a set of related lines and collectively representing the Ruiru 11 cultivar. Twenty-one full-sib families representative of this hybrid cultivar grown in Kenya in five sites exhibiting strong edaphic and climatic differences were used for the study. Rainfall amounts during various phases of berry development were used to explain the differences observed in the discriminating abilities of the locations for bean and liquor traits. The results showed that these families were best differentiated for bean sizes in the site where moisture supply was optimal throughout berry expansion and filling stages, whereas discrimination on the basis of liquor traits were best observed in the site where moderate moisture stress occurred during bean filling stage. The overall precision in prediction of family values was low for liquor qualities; but a much more efficient selection for large bold beans, optimally based on the AA grade was shown to be possible. Selection indices for family selection were computed to realize a trade-off between genetic gains in bean size and liquor flavour.

Agronomic and physiological responses of sorghum, maize and pearl millet to irrigation

Sorghum, maize and pearl millet were grown for fodder on a sandy loam soil under four irrigation schedules (i.e. irrigation at ID/CPE = 1.0 (S 0), 0.6 (S 1), 0.3 (S 2), 0.15 (S 3), where ID is irrigation depth, and CPE is cumulative evaporation from a USWB Class-A pan) during the hot dry season (May–July). Dry matter yield did not differ significantly among the three species under wet condition (S 0), but sorghum was superior to maize under all levels of water deficit (S 1, S 2, S 3). Sorghum also outyielded pearl millet under moderate moisture stress (S 1, S 2), but dry matter yields in the two species were similar under drought condition (S 3). Water-use efficiency was highest under wet (S 0), moderately stressed (S 2) and severely stressed (S 3) conditions in maize, sorghum and pearl millet, respectively. Apparent water use was highest from the upper soil layers, especially under frequent irrigation (S 0). Among stressed plants (S 3), maize extracted more water than the other species from the top soil (0–45 cm) and sorghum from the sub-soil (45–135 cm), while pearl millet had small water uptake from all layers of the soil profile. Increased frequency of irrigation generally resulted in higher profile water content, leaf water potential ( ψ L), leaf osmotic potential ( ψ π ), leaf turgor potential ( ψ P), leaf diffusive conductance (K L), leaf area index (LAI), evapotranspiration (ET), canopy net photosynthesis (P N) and dry matter yield in all species. ψ π decreased over time after planting, and irrigation only partially arrested the reduction in ψ π . ψ P generally declined with ψ L and at a more rapid rate in maize than in sorghum and pearl millet. Maize had higher ψ L and lower K L than sorghum and pearl millet. K L was correlated with both profile water content and ψ P in all species. There was significant positive linear association amongst LAI, ψ P, ET and P N in the three species. Sorghum had, however, higher P N and ET per unit LAI than maize and pearl millet. The dry matter yield was also positively linearly related to ψ P, K L, ET and P N in ascending order of prediction. Thus, P N seems to be the best parameter for assessing dry matter production in the three species. The study has emphasized that sorghum should be grown as fodder crop under inadequate and irregular water supply in semi-arid regions.

Growth and morphology of western red cedar seedlings as affected by photoperiod and moisture stress

One-year-old container-grown seedlings of western red cedar (Thujaplicata Donn) were subjected to short days (8 h) and moisture stress, applied separately and in combination, and compared with untreated seedlings. The treatments were applied at various times during the growing season and lasted 2 and 4 weeks. Short days slowed height growth only when applied during the most rapid period of shoot elongation in late June and early July. Short days combined with moisture stress always reduced the final height regardless of the time and duration of applied treatments. Moderate moisture stress applied alone in mid-August hastened root dry weight gain but did not affect other morphological characters. The applied treatments had no lasting effects upon mitotic activity of terminal shoot apices and resulted in no differences in the timing of fall cessation of mitotic activity. The study describes details of the 1st-year growth of containerized western red cedar seedlings that were not subjected to the above specified treatments. It reports on growth rates for several morphological characters, such as height, number of stem units, root collar diameter, and shoot and root dry weights. Also, apical transitions in leaf initiation, stomatal distribution on leaf and cotyledon surfaces, and leaf wax features are described.

Effects of moisture stress on stomatal resistance and photosynthetic rate in cotton ( Gossypium hirsutum) 1. Controlled levels of stress

The effects of moisture stress on stomatal resistance and on photosynthetic rate were studied in cotton ( Gossypium hirsutum L., cv. Acala SJ-2) under field conditions with drip irrigation in 1984 and in 1985. Moisture stress was evaluated by measuring the minimum midday leaf water-potential, which was kept at two levels (−1.6 and −2.4 MPa) during each of two phenological periods. Stomatal resistance increased and photosynthetic rate decreased as a result of moisture stress. The correlation between stomatal resistance and radiation was lower when the plants were subjected to moisture stress. An exponential asymptotic relationship was found between photosynthetic rate and stomatal resistance. Stomata were found to limit the photosynthetic process in well-watered plants or in midly stressed plants, while mesophyll resistance was the main factor reducing it under more severe moisture stress. In the moisture-stressed plants, mesophyll resistance increased more than did stomatal resistance, and this was associated with a higher internal CO 2 concentration in the leaf ( C i) and a lower ratio of photosynthetic rate to C i. Under moderate moisture stress the maximum photosynthetic rate was attained at an earlier leaf age, while a more severe stress resulted in a lower photosynthetic rate at all leaf ages.

Interaction Between Moisture Stress and Potato Leafhopper (Homoptera: Cicadellidae) Damage in Alfalfa

The combined and independent consequences of moisture stress and potato leafhopper (PH), Empoasca Fabe Harris, injury on alfalfa, Medic ago saliva L., quality were investigated under controlled conditions. Plant water potentials, percentage of crude protein, and free amino acid profiles were determined in PLH-infested and non infested alfalfa exposed to three soil moisture deficit levels. Results suggest an interaction between moisture stress and PH injury. PH feeding had no effect on water potentials of either severely water-stressed or amply watered plants. However, PLH-infested alfalfa under mild soil moisture deficits (-0.07 omega pascals [MPa] soil moisture tension) showed a reduced ability to imbibe water compared with non infested plants. Although PH feeding and soil moisture deficit independently decreased crude protein levels in alfalfa, PH feeding and moderate moisture stress (-0.5 to -1.2 ma soil water tension), when combined, reduced crude protein levels further than moderate moisture stress alone. Individual free amino acid concentrations, in general, were reduced, but praline concentrations showed marked increases caused by both types of stress. In one trial, total amino acid concentrations were significantly reduced by PH feeding alone. Soil water deficits and PH feeding, individually or combined, reduced total amino acid concentrations when praline was subtracted from the total. Plant water potential, percentage crude protein, and free amino acid concentration are indirect measures of alfalfa growth. Because these parameters apparently are influenced by PH feeding and water stress, independently and by interaction, these factors should be considered when determining economic injury levels and thresholds for PH in alfalfa.

Injury and Yield Response of Soybean to Chronic Doses of Ozone and Soil Moisture Deficit1

A 2‐yr field study was performed near Raleigh, NC, to determine injury and yield response of soybean [Glycine max (L.) Merr. ‘Davis’] to long‐term O3 exposure and soil moisture deficit. Two levels of soil moisture [well‐watered (WW) and water‐stressed (WS)] were tained by differential irrigating during periods of low precipitation. Open‐top field chambers were used to expose plants to different levels of O3 for 109 days. The 1983 season was drier and hotter than the 1984 season. In 1983, plants in the WS plots were under moderate to severe moisture stress from shortly after planting (V2) until midway through flowering (R3) and they yielded approximately half as much as those in the WW plots. In 1984, plants in the WS plots were under moderate moisture stress during flowering and pod‐fill stages and they yielded 20% less than those in the WW plots. In 1983, there was a significant relationship between O3 concentration and yield in the WW plots, but not in the WS plots. In 1984, similar linear responses to O3 occurred at both levels of soil moisture. Compared to yield in the charcoal‐filtered‐air (control) treatment (2‐yr 7 h day−1 mean O3 concentration of 0.027 μL L−1), predicted yield loss for WW plots at ambient O3 levels (2‐yr 7 h day−1 mean of 0.054 μL L−1) was 12% in 1983 and 14% in 1984. The predicted loss value for the WS plants in 1984 was 12%.

The effect of moderate moisture and nutrient stress on bud formation and growth of container-grown white spruce seedlings

Piceaglauca (Moench) Voss seedlings were grown in controlled environment rooms following germination with a combination of fluorescent and incandescent lamps (ratio, 1.4:1) providing 390 μmol s−1 m−2 of photosynthetically active radiation over a 24-h photoperiod. Moderate moisture and nutrient stress treatments were applied to separate seedling groups (10 weeks from germination) for a 2-week period during the initial free growth phase when mean seedling shoot length had reached 12 cm. Photoperiod was then reduced to 8 h. Both periodic moisture stress (reaching −1.72 MPa) and nutrient withdrawal (N, P, K) were effective in inducing terminal bud formation in container-grown white spruce seedlings under nonlimiting photoperiod and the number of needle primordia subsequently formed in the terminal bud under short days was significantly reduced. However, decreased needle complements in the stressed seedlings did not result in reduced shoot growth in the second growing season. Free growth following extension of the preformed shoot compensated for the reduced amount of predetermined foliage.

Effect of Moisture Stress on Wild Oat (Avena fatua) Response to Diclofop

The effect of moderate moisture stress on the activity of the methyl ester of diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} applied to wild oat (Avena fatuaL.) and the influence of morphological and physiological factors on the activity of the herbicide on stressed plants were investigated in growth-room experiments. Wild oat was grown in very fine sandy loam brought to a gravimetric soil moisture content (SMC) of 20% (water potential of -0.3 bars) or 10% (-6.5 bars) prior to herbicide treatment. The activity of diclofop on wild oat was slightly, but significantly, reduced when the SMC was increased from 10 to 20% immediately after spraying. Maintaining the SMC at 10% after spraying further reduced the activity of the herbicide. Wild oat plants grown at 20% SMC had 22% greater leaf area and retained 23% more herbicide than plants grown at 10% SMC. Penetration of the methyl ester of14C-diclofop into wild oat grown at 20 or 10% SMC did not differ significantly 12, 24, or 48 h after application. Stressed and unstressed plants did not differ significantly in the metabolism of the methyl ester of14C-diclofop. However, growth at a low SMC prior to treatment decreased the proportion of the radiolabeled herbicide recovered in the apex, third leaf, and tillers of wild oat. This may partially account for the reduced activity of this herbicide on wild oat subjected to moisture stress.

Changes in mitotic index during onset of dormancy in Douglas-fir seedlings

A method is presented for rapid determination of the mitotic index in terminal buds of Douglas-fir, Pseudotsugamenziesii (Mirb.) Franco. Fertilization at planting increased mitotic index but fertilized seedlings entered dormancy at the same time as unfertilized seedlings. Cold storage, prior to dormancy, reduced mitotic index rapidly and was related to reduced height growth the following year. The effects of moderate moisture stress and seed source on mitotic index were slight.

Some effects of rust infection and moisture stress on growth, diffusive resistance and distribution pattern of labelled assimilates in sunflower

Greenhouse experiments, where sunflower plants (cv. Peredovic) were inoculated with Puccinia helianthi at the vegetative stage of plant growth, showed that the effect of rust on growth parameters varied according to the moisture stress to which plants were subjected. Rust infection caused a marked reduction in the diffusive resistance of leaves in darkness. However, the diffusive resistance in light of leaves not stressed or subjected to mild moisture stress was unaffected by rust infection. In uninfected plants subjected to moderate moisture stress, the diffusive resistance in light increased markedly, whereas in rust-infected leaves it remained the same as in leaves not stressed or subjected to mild moisture stress. Carbon-14 uptake by the first pair of true leaves of non-stressed plants or those subjected to mild moisture stress was unaffected by a low level of rust infection (9% disease rating). Carbon-14 uptake by uninfected leaves was reduced when they were subjected to moderate moisture stress. Rust infection and moderate moisture stress caused a reduction in the rate of translocation of labelled assimilate from leaves fed with 14CO2 and also altered the distribution pattern of labelled translocate to various sinks.

Effect of moisture stress on the ethephon response in tomatoes

Potted plants (cultivar ‘Napoli’) were maintained at 3 levels of moisture (continuously moist, moderate moisture stress and severe moisture stress) and sprayed to run-off with 3 levels of ethephon (0, 250 and 500 p.p.m.) in factorial combination, in order to examine the effect of moisture status on the ethephon-accelerated ripening-response in tomatoes. The largest increases in ripening-rate occurred where plants were moderately stressed and sprayed with 250 p.p.m. ethephon, or where plants were kept continuously moist and sprayed with 500 p.p.m. ethephon. No substantial increase in ripening-rate occurred at higher levels of either ethephon or moisture stress. Leaf senescence was rapid in all treatments other than the moderately stressed and continuously moist controls. In some of the water-stressed treatments a partial recovery of plant water potential occurred as a result of reduced transpiration due to rapid and extensive leaf loss.

Water Consumption of Cucumbers during Vegetative and Reproductive Stages of Growth1

Abstract The best irrigation schedule for pickling cucumbers (Cucumis sativus L.) involved removal of between 48 and 64% of the available water in the upper 90 cm of the soil profile between irrigations. The ratio (Kc) of consumptive water use to evaporation pan loss reached a maximum of 1.5 during the early harvest season. Moderate moisture stress had no significant effect on the grade or number of poorly developed fruit. Transpiration rate (ml/cm2), leaf area, water use pattern, and total water use were compared in greenhouse and growth chamber environments for fruiting and nonfruiting cucumbers. Transpiration rate was higher and leaf area smaller for fruiting plants. Fruit production did not significantly affect total water consumption or the seasonal water use pattern.

Variation in Drought Tolerance in Eucalyptus viminalis Labill

Six-month-old seedlings of two low rainfall populations of Eucalyptus viminalis showed greater resistance to desiccation and were less damaged by sustained drought than seedlings from two high rainfall populations. The more resistant seedlings did not simply avoid drought by quickly closing stomata, but were capable of maintaining relatively high rates of transpiration under moderate moisture stress. The two populations from moist habitats wilted at a higher relative turgidity of leaves than did the populations from the drier habitats. Furthermore, for populations from one dry habitat and one moist habitat, changes in relative turgidity in relation to water potential of leaves during drying were not significantly different. It is suggested that the greater tolerance of the low rainfall populations to drought is related to physiological resistance of the protoplasm to desiccation. Some differences in drought resistance were also noted between the two low rainfall populations. Young seedlings (3 months old) from a population on a deep basalt-derived soil were less resistant than young seedlings from a neighbouring population on a shallower granite soil. It is suggested that the selection for drought tolerance at the granite site has been more severe than at the basalt site.

Growth Patterns of Irrigated Sugarbeet Roots and Tops1

AbstractElectronic growth sensors were used in the field near Amarillo, Texas, to obtain continuous records on strip chart recorders of the root and top growth of irrigated sugarbeets (Beta vulgaris). The purpose of the study was to characterize the typical diurnal variation in growth rate of the crop and to determine its growth response to variations in ambient atmospheric and soil conditions. The growth sensors were potentiometers, either constructed in the form of slidewire discs or adapted from commercial linear transducers. The root sensors were operated by a pulling action of a noose surrounding the root. The height sensors were rotating slidewire discs attached with fine wires to leaf tips.The growth patterns of sugarbeet roots and tops were very similar with most of the growth occurring at night. The main difference was a decrease in size of roots during the daytime that did not occur with leaves.On a typical day with few clouds in July or August and with the plants under a moderate moisture stress, the growth rate of roots and tops accelerated suddenly about an hour before sunset and reached a peak or maximum point around sunset. Growth continued at a high rate during the night. The growth rate of roots usually reached a secondary peak between midnight and sunrise. The growth rate of roots and tops decreased rapidly after 7 to 8 A.M. and little or no growth took place during the middle of the day. The normal dear−day growth pattern was altered by high moisture stress as well as by cloudiness and rain showers.