Osmotic Adjustment and Stomatal Response to Water Deficits in Maize

A pot experiment was carried out using five maize {Zea maysL.) cultivars under three soil moisture levels (MPa 0 to –0.05,–0.3 to –0.9 and –1.2 to –1.5) to investigatethe effects of water deficits on osmotic adjustment and stomatalconductance. The degree of leaf rolling and the sugar and nutrientconcentrations in leaf cell sap were measured. Leaf water potential and osmotic potential decreased and stomatalconductance decreased with increasing water deficits. Stomatalconductance correlated positively with leaf water potentialand osmotic potential. Degree of leaf rolling was lower in cultivarswhich maintained higher turgor. Osmotic adjustment of 0.08 to0.43 MPa was found under the lowest soil moisture level in fivecultivars used. Sugar and K were the major osmotic substancesin the maize plant. Sugar, K and Mg concentrations increasedunder water deficit, and correlated negatively with a decreasein osmotic potential. Key words: Zea mays L., leaf water relations, leaf rolling, osmotic adjustment, stomatal conductance, water deficit     

Response of Indoor-Grown Cassava to Water Deficits and Recovery of Leaf Water Potential and Stomatal Activity after Water Stress

Wilting of the leaves occurred in acropetal succession at leafwater potentials between –0.9 and –1.1 MPa. Onlysevere water stress caused the discoloration and abscissionof the basal leaves. Leaf resistance was independent of leafwater potential above –0.5 MPa but increased as the potentialdropped below this value. When the stressed plants were rewatered,leaf water potentials recovered rapidly within the first h.Subsequently, the rate of recovery declined gradually. The maximumvalue of leaf water potential after rewatering was dependenton the severity of the water stress.     

Stomatal Response of Citrus jambhiri to Water Stress and Humidity

Seven-month-old rough lemon (Citrus jambhiri Lush.) seedlings were subjected to high- and low-humidity treatments (vapor pressure deficits of 8.0 and 19.6 mbar) for 3 weeks. Half of each group was well supplied with water and half was subjected to a series of three drying cycles in which xylem pressure potential fell to below ?25 bar. The relationship between leaf conductance and xylem pressure potential was similar during each drying phase and was unaffected by atmospheric humidity. Several days elapsed after rewatering before normal stomatal opening occurred. When all the plants were subsequently kept well watered, leaf conductances decreased as the leaf-to-air vapor pressure difference was increased. However, the conductances of previously stressed plants were lower than those of unstressed plants, and consequently previously stressed plants had lower transpiration rates.     

Abaxial and Adaxial Stomatal Density, Stomatal Conductances and Water Status of Bean Primary Leaves as Affected by Paclobutrazol

The plant growth retardant, paclobutrazol at 8.5 or 17.0 μM concentrations effectively inhibited the stem elongation and primary leaf expansion of bean seedlings. Although the retardant reduced the relative water content in well-watered plants, the water and pressure potentials remained high in the primary leaves. K⁺, Na⁺, Mg²⁺ and Ca²⁺ contents in the primary leaves of the paclobutrazol-treated plants were not significantly different from those in the control. The stomatal density increased on both surfaces but the length of guard cells was not reduced significantly on the adaxial epidermes of the paclobutrazol-treated primary leaves. The inhibitory effect of paclobutrazol on the abaxial stomatal conductances became more pronounced with time during the light period but the adaxial surfaces displayed similar or slightly higher conductances than those of the control. The transpiration rate on a unit area basis did not change significantly or increased in the treated leaves thus the reduced water loss of paclobutrazol-treated plants was due to the reduced leaf area. Stomatal conductances of the adaxial surfaces responded more intensively to exogenous abscisic acid and the total leaf conductance decreased faster with increasing ABA concentration in the control than in the paclobutrazol-treated leaves. Paclobutrazol, an effective inhibitor of phytosterol biosynthesis, not only amplified the stomatal differentiation but increased the differences between the adaxial and abaxial stomatal conductances of the primary leaves.     

栽培稻及其近缘野生种间杂交揭示杂草稻的起源

通过水稻种间、亚种间和品种间的杂交,在套袋隔离和自然授粉两种条件下,对其杂交亲本主要农艺性状类型及杂交后代群体中杂草稻发生频率、类型及主要特征以及杂草稻的发生趋势进行调查分析,直接验证和重演杂草稻起源的主要路径。杂草稻的主要特征为:颖壳褐色或金色,种皮红色,散穗、易落粒,中长芒或无芒。结果表明,如果以近缘野生种为亲本,在其F2群体中比较容易发生类似杂草稻的单株;杂交组合中杂草稻出现频率的大小依次为:杂草稻或野生稻/粳稻(44.16%)>杂草稻或野生稻/籼稻(27.84%)>籼稻/粳稻(3.30%)>籼稻/籼稻(1.41%)>粳稻/粳稻(0)。这一结果显示杂交亲本间遗传差异越大,在后代中出现杂草稻类型植株的频率就越高。套袋条件下,后代中杂草稻出现的频率为10.70%,而不套袋情况下为4.90%。     

Cell Membrane Stability and Leaf Surface Wax Content as Affected by Increasing Water Deficits in Maize

A field experiment was conducted with a water-stressed treatmentand well-watered control using eight maize (Zea mays L.) cultivars.Effects of water deficits on cell membrane stability (CMS) measuredby the polyethylene glycol (PEG) test, leaf surface wax content,and relative growth rate were investigated. Cytoplasmic lipidcontent was also analysed. Cell membrane stability and leaf surface wax content increasedwith the degrees of stress. Tolerance to drought evaluated asincrease in CMS under water deficit conditions was well differentiatedbetween cultivars and was well correlated with a reduction inrelative growth rate under stress. A negative correlation wasfound between percentage injury in the PEG test and leaf surfacewax content. High phospholipid contents were observed in tissuesof drought tolerant cultivars under water deficit conditions. Key words: Cell membrane stability, cytoplasmic lipid, drought tolerance, leaf surface wax, relative growth rate     

Stomatal Responses to Water Deficits and Abscisic Acid in Leaves of Sunflower Plants (Helianthus annuus L.) Grown under Different Conditions

The decrease in diffusive conductance of a leaf exposed to waterstress or to exogenous abscisic acid (ABA) was smaller in leavesof sunflower plants (Helianthus annuus L. cv. NK285) that hadbeen grown in a phytotron in humid air than in leaves of sunflowersgrown outdoors. Stomata of the phytotron-grown plants were slowerto close after detachment of a leaf than those of the outdoorplants. When stomata closed rapidly, as they did in detachedleaves and after treatment with ABA, the extent of closure wasvaried over the leaf's surface, in particular in the case ofphytotron-grown plants, and the extent of the heterogeneitywas greater in the phytotrongrown plants than in the outdoorplants. When stomata closed gradually, for example, under conditionsof limited moisture in the soil, closure occurred uniformlyover leaves of plants of both types. The smaller decrease indiffusive conductance of leaves from phytotron-grown plantsafter treatment with ABA resulted from the presence of patcheson the surface in which stomata remained open. The smaller decreaseof diffusive conductance in the phytotron-grown plants underconditions of limited moisture in the soil resulted from theuniformly lower responsiveness of stomata on a leaf to the decreasein water potential. When estimates are made of the intercellularconcentration of CO₂ (Ci) from gas-exchange measurements, heterogeneityin stomatal closure should be monitored when stomata close rapidly,in particular in plants grown in humid air, because heterogeneousstomatal closure can lead to overestimates of Ci. (Received April 18, 1994; Accepted May 25, 1995)     

Leaf Age as a Determinant in Stomatal Control of Water Loss from Cotton during Water Stress

The stomatal resistance of individual leaves of young cotton plants (Gossypium hirsutum L. var. Stoneville 213) was measured during a period of soil moisture stress under conditions of constant evaporative demand. When plants were subjected to increasing soil water stress, increases in stomatal resistance occurred first on the lower leaves and the stomata on the upper surfaces were the most sensitive to decreasing leaf-water potential. Stomatal closure proceeded from the oldest leaves to the youngest as the stress became more severe. This apparent effect of leaf age was not due to radiation differences during the stress period. Radiation adjustments on individual leaves during their development altered the stomatal closure potential for all leaves, but did not change the within-plant pattern. Our data indicate that no single value of leaf water potential will adequately represent a threshold for stomatal closure in cotton. Rather, the stomatal resistance of each leaf is uniquely related to its own water potential as modified by age and radiation regime during development. The effect of age on stress-induced stomatal closure was not associated with a loss of potassium from older leaves. Increases in both the free and bound forms of abscisic acid were observed in water-stressed plants, but the largest accumulations occurred in the youngest leaves. Thus, the pattern of abscisic acid accumulation in response to water stress did not parallel the pattern of stomatal closure induced by water stress.     

Comparison of Embryo Development in Wild and Cultivated Arachis Species

Embryo development following selfing was investigated in twowild diploid peanut species, Arachis batizocoi Krap. et Greg.(coll. K 9484) (2n = 20) and A. duranensis Krap. et Greg. nom.nud. (coll. K 7988) (2n = 20), and one cultivated tetraploidspecies, A. hypogaea L. NC-Ac 18000 (2n = 40). Rates of pegelongation and sequences of embryo development for each specieswere compared. Peg elongation rates were similar for the twowild species, but for A. hypogaea it was only one-third to one-halfthat of the diploid species. Embryos in A. hypogaea showed slightlymore rapid cell division than in the wild species. The observedvariation in reproductive development between the wild and cultivatedspecies indicate that different control mechanisms may governdevelopment in the different species and may be at least partiallyresponsible for failure to produce viable interspecific hybridsat various ploidy levels. The observations are also importantfor determining the time at which embryos of different speciesof Arachis will reach the appropriate stage of development forsuccessful culture on an artificial medium during embryo rescueprocedures. Peanut, Arachis hypogaea, wild species, embryo, peg     

Chloroplast DNA Diversity in Populations of Wild and Cultivated Barley

Chloroplast DNA (cpDNA) diversity was found within and among populations (245 accessions total) of wild barley, Hordeum vulgare L. ssp. spontaneum Koch from Israel and Iran. Three polymorphic restriction sites (HindIII, EcoRI, BclI) which define three distinct cpDNA lineages were detected. One lineage is common to populations in the Hule Valley and Kinneret of northern Israel, and in Iran. The second lineage is found predominantly in the Lower Jordan Valley and Negev. The distribution of the third lineage is scattered but widespread throughout Israel. Sixty two accessions of cultivated barleys, H. vulgare L., were found, with two exceptions, to belong to just one cpDNA lineage of wild barley, indicating that the cpDNA of cultivated barley is less variable than its wild ancestor. These results demonstrate the need for assessing intraspecific cpDNA variability prior to choosing single accessions for phylogenetic constructions at the species level and higher.     

黑水缬草野生变家植及其栽培技术

本文描述了黑水缬草的植物形态及生活习性;重点介绍了黑水缬草野生转家植的研究与实践,文章中叙述的套袋收集种子的方法很有实用价值;采用变温结合赤霉素处理种子,打破黑水缬草的种子休眠技术,提高了出芽率,取得了较为理想的效果:文章中还阐述了二次移栽和病虫害防治及采收加工的关键技术。     

Control of Growth and Reproduction in Cultivated and Wild Rice by Light Quality and Dark Period

One cultivated and two wild rice varieties have been subjectedto variation in photoperiod and light quality by daily exposureof the seedlings at the four-leaf stage to 8 h of natural daylightfollowed by white incandescent, red, green or blue light for2,4 or 8 h in a temperature and humidity-controlled growth chamber.In some cases far-red irradiation was applied after white orred for 1 and 2 h. The treatments caused marked differencesin growth and reproduction between the cultivated and wild rices.The cultivar Dudkalmi showed extensive tillering after far-redexposure. Earliest flowering was observed with a 16-h dark periodboth in the cultivated and wild rices. Failure of floweringwith and 8-h day and 8-h artificial light of different wavelengthscould be overcome by red or far-red of 1-h duration. The lightquality interacted differently with the dark period in the accelerationof flowering in the three varieties. In another experiment theeffects of interruption of the dark period by a light periodof 2 h after from 4–12 h of darkness in a 24-h cycle werestudied in the two wild rice varieties. Light of different wavelengthsinterposed in the dark period caused variation in tiller numberand stem length in comparison to an uninterrupted dark periodof 16 h. The effect at the beginning of the dark period wasearlier flowering; flowering was delayed by interruption at4 h and inhibited after 8 h but accelerated after a 10- to 12-hdark period. The results are discussed in the light of the significanceof the dark period and light quality in regulating hormone balanceand phytochrome reactions.     

Age-related Changes in Stomatal Response to Cytokinins and Abscisic Acid

Kinetin and zeatin(100 mmol m^–3)reversald the ABA-mediated(100mmol ^m-2)closure of stomata of young maize leaves but did notaffect stomatal apertures of these leaves when applied alone.As leaves aged, kinetin or zeatin alone promoted increased stomatalapertures, while abscisic acid (ABA) applied alone had a reducedeffect on stomata. Even with older leaves, cytokinins reversadthe effect of ABA on stomata. Maize, stomata, abscisic acid, kineusc, zeatin, Zea mays     

Stomatal length and frequency as a measure of ploidy level in black wattle, Acacia mearnsii (de Wild)

The length and frequency of stomata on leaf surfaces were examined as rapid techniques for future identification of ploidy level of Acacia mearnsii (de Wild). Diploid (2 n  = 2 x  = 26) and tetraploid (2 n  = 4 x  = 52) plants were germinated from chipped seed at 25°C and grown under nursery conditions. After one month, measurements showed that the mean stomatal length was 27.17 ± 0.474 µm for diploids and 40.24 ± 0.521 µm for tetraploids and these differed significantly from each other ( P  < 0.001). The frequency of stomata per leaf surface was shown to decrease significantly ( P  < 0.001) as the ploidy level increased, with a mean of 22.11 ± 0.495 for diploids and 10.26 ± 0.495 for tetraploids. It was concluded that stomatal length and stomatal frequency are rapid indirect methods to identify ploidy level in black wattle.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 177–181.     

Direct Control of SPEECHLESS by PIF4 in the High-Temperature Response of Stomatal Development

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Quantitative Comparison of Ginsenosides and Polyacetylenes in Wild and Cultivated American Ginseng

Quantitative comparison of seven ginsenosides in wild and cultivated American ginseng revealed that the Rg₁/Rd ratio presented a significantly large difference between cultivated and type‐I (one of the defined chemotypes) wild American ginseng, facilitating this ratio as a characteristic marker for differentiating these two groups. Similarly, the ratio (Rg₁+Re)/Rd, and the ratio of protopanaxatriol (PPT)‐type ginsenosides to protopanaxadiol (PPD)‐type ginsenosides showed a large difference between these two groups. On the other hand, type‐II wild samples were found to have high Rg₁/Rb₁ and Rg₁/Re ratios and low panaxydol/panaxynol ratio, which is entirely different from Type‐I American ginseng, but is very similar to that of Asian ginseng. This not only suggests that the chemotype should be taken into consideration properly when using these parameters for differentiating American and Asian ginseng, but also indicates that type‐II wild American ginseng may have distinct pharmacological activities and therapeutic effects.     

Different Effects of Wild and Cultivated Soybean on Rhizosphere Bacteria

Microbiology - Wild varieties of plants have stronger stress resistances than their cultivated relatives, and rhizosphere bacteria play an important role in improving the environmental...