Differences In Drought Resistance Research Articles

Genotypic Response of Common Bean (Phaseolus vulgaris L.) to Moisture Stress Conditions in Kenya

The aim of this study was to determine drought response of thirty bean genotypes under glasshouse and field conditions (Kenya) during 1994. The experiment was laid in a Randomized Complete Block in split-plots design with three replications. Significant (p<0.05) genotypic differences in drought resistance were observed under moisture stress conditions. Significant interaction (p<0.01) between variety and moisture level were observed both in the glasshouse and in the field. Drought resistant genotypes showed high relative water content in stress environment as compared to susceptible ones. They also took relatively longer time to wilt, consequently showing low soil water content at wilting and lower biomass reductions under moisture stress conditions. A significant negative correlation was obtained between days to permanent wilting and relative water with biomass reduction. Relative water content was positively and significantly correlated to stomatal conductance and days to permanent wilting. Correlation between stomatal conductance and biomass yield reduction was not significant. The responses relative water content and stomatal conductance, in certain conditions, were recognized as beneficial drought resistance indicators and may be used as selection criteria in bean breeding programme

Genetic engineering of drought-resistant tobacco plants by introducing the trehalose phosphorylase (TP) gene from Pleurotus sajor-caju

This study generated transgenic tobacco plants expressing trehalose phosphorylase of Pleurotus sajor-caju (PsTP) constitutively under the control of the cauliflower mosaic virus (CaMV) 35S promoter. Sixteen transgenic lines were selected by genomic Southern blot analysis for further study. Unlike yeast TPS1-transformed or Escherichia coli TPS1-transformed tobacco or potato, all of the PsTP transgenic tobacco lines showed normal growth phenotypes both in the culture tubes and soil mixture. The study measured the trehalose contents of PsTP-transformed tobacco plants as well as the wild type and empty vector-transformed control plants. Results showed that the PsTP transformant contained 6.3 μmol g−1 of plant tissues, while the wild type and the control plants had only minimal levels of trehalose. Because this study detected a significant amount of trehalose in PsTP transgenic tobacco plants, it decided to carry out a bioanalysis of the PsTP transgenic tobacco plants by drought treatment by not watering the plants for over 10 days. A significant difference in drought resistance was observed from the second nonwatering day between the transgenic and the control tobacco plants. The transgenic tobacco plants had normal growth and did not wither, while the wild type and the only empty vector-transformed control plants withered severely. Among all the transgenic lines, line 10-4 showed the strongest resistance to drought stress. It did not wither even after 10 days without watering. In addition, when the drought resistance of PsTP transgenic tobacco plants was tested using detached leaves, most transgenic plants, except one line, showed better capacity to retain water than the empty vector-transformed transgenic plant.

Responses of Acacia tortilis and Acacia xanthophloea to seasonal changes in soil water availability in the savanna region of Kenya

Comparative field studies were conducted on Acacia tortilis (Forsk.) Hyne and Acacia xanthophloea Benth. trees growing in a semi-arid environment in Kibwezi, Kenya, to assess root access to soil water at varying soil depths and how this may affect the expression of morphological and physiological traits developed during drought. Measurements of soil water content, leaf growth, shoot elongation, sap flow in the xylem of stems and branches, leaf water potential, leaf transpiration and stomatal conductance were carried out. Further, water use efficiency (WUE) over long-term periods was examined via carbon isotope discrimination (δ 13C) on leaves. Whole tree and leaf specific hydraulic conductance were determined from sap flux or leaf transpiration and the water potential gradient between soil (as predawn potential) and canopy, respectively. Leaf growth and shoot elongation depended on soil water availability (SWC) and plant tissue water status. A. xanthophloea showed greater (40 kg d −1) water use compared to A. tortilis trees of comparable sizes (20 kg d −1) during favorable conditions of SWC. Decline in SWC reduced water use and the onset and rate of decline in sap flux was determined by the rooting depth. A. xanthophloea showed earlier response (onset at SWC=0.24 m 3 m −3) to water stress than A. tortilis (onset at SWC=0.14 m 3 m −3). Midday depression in stomatal conductance and subsequent decline in transpiration during favorable SWC as observed in A. xanthophloea was attributed to increased hydraulic resistance and stomatal closure. Rooting patterns and root characteristics could account for the observed morphological and physiological differences between A. tortilis and A. xanthophloea as well as between small and large A. tortilis trees. However, seasonal responses were modified by species-inherent characteristics, which are expressed during drought. Access to deeper soil water resources and the abilities of trees to extract and efficiently transport water may explain differences in drought resistance among species and tree distribution in the arid savanna.

Drought resistance of native and introduced perennial grasses of south-eastern Australia

Perennial grasses are the key to the economic and environmental sustainability of pastures for livestock grazing in south-eastern Australia. Mortality of perennial grasses can occur during drought periods and there is anecdotal evidence of differences in drought resistance among species, but information on the basic ecophysiological responses of these species to drought is lacking. An experiment was conducted to determine the responses of 7 native and 3 introduced perennial grass species to continuous drought. Leaf survival during severe drought varied among the species nearly 4-fold, from 11 to 40 days, and was considered a measure of their overall drought resistance. All of the species had good dehydration tolerance, so the differences in drought resistance were related more to their dehydration avoidance traits, specifically to the amount of water available to the plant at the point where plant transpiration became minimal. The native species had both the longest and shortest leaf survival periods, with the introduced species ranking intermediate. Species exhibited various morphological traits that contributed to dehydration avoidance during severe drought, including leaf folding or rolling, rapid leaf shedding, and large amounts of cuticular wax. The results are discussed in terms of their implications for perennial grass persistence in south-eastern and in south-western Australia.

Differential Drought Responses of Faba Bean (Vicia faba L.) Inbred Lines

Drought responses of 19 inbred faba bean lines of different origin were studied in the field under rain shelters with and without irrigation. Inbred lines differed significantly in response to drought (P &lt; 0.01): those with a lower drought sensitivity index (SI) (more resistant) originated from the drought‐prone regions characterized by smaller plant size (r = 0.93), and more pods and seeds per plant (r ≥ 0.90) regardless of seed size, while lines with higher SI (more sensitive) were those which mainly exhibited higher yield under favourable conditions accompanied by a greater biomass. In a greenhouse experiment under mild drought (−0.15 MPa soil water potential), comparisons between relatively drought‐sensitive (Adriewaalse) and drought‐resistant (L7) inbred lines showed that Adriewaalse used 38 % more water than L7 and also produced 40 % more biomass. There was a stress‐induced decrease in osmotic potential (ψs) in both lines (by 0.72 and 0.50 MPa for Adriewaalse and L7, respectively) accompanied by decreased turgor in Adriewaalse and increased turgor in L7. The difference in drought‐induced solute accumulation between lines was diminished when solute accumulation due to water loss and growth inhibition was considered, which indicates that solute accumulation was the result of a concentration effect. Similarly, lower SI in the field was not the result of osmotic adjustment, as the relationship between SI and drought‐induced decrease in ψs was negative. The water use efficiency of both inbred lines increased markedly with increasing water deficit, though there was no difference between the lines. It was concluded that differences in drought resistance between these inbred faba bean lines were manifested through plant size‐induced water demand (avoidance) but were not associated with osmotic adjustment (tolerance).

Drought resistance of two hybrid Populus clones grown in a large-scale plantation.

Poplar hybrids were grown with irrigation in a large-scale plantation to investigate the mechanisms underlying clonal differences in drought resistance. Beginning in spring 1992, Populus trichocarpa x P. deltoides (TD) and P. deltoides x P. nigra (DN) cuttings received 46, 76, or 137 cm year(-1) of irrigation to supplement the 18-20 cm of annual precipitation, and all trees received the same fertilization regime. Stem volume, assessed as the square of stem diameter at breast height times tree height (D(2)H), and water relations of the trees were studied from the end of their second growing season until the end of their fifth growing season. By the end of the second growing season, stem volume of Clone TD was 40-146% larger than that of Clone DN, but stem volume growth was independent of irrigation in excess of 46 cm year(-1) in both clones. During the third growing season, stem volume growth of both clones was limited by both the 46- and 76-cm irrigation treatments, so that by the end of the third growing season trees in the 46-cm irrigation treatment were only half the size of trees in the 137-cm irrigation treatment. These treatment differences were maintained through the fifth growing season. Although stem volumes of Clone TD trees in the 76- and 137-cm irrigation treatments were larger than the corresponding values for Clone DN trees at the end of the third growing season (1994), these clonal differences gradually decreased in subsequent years and were not detectable after 5 years, because stem volume relative growth rate of Clone DN was greater than that of Clone TD in all treatments. Although both clones exhibited similar predawn leaf water potentials, Clone DN typically maintained higher midday leaf water potentials, suggesting better stomatal control of water loss. Clonal and treatment differences in osmotic potential at full turgor were minimal and could not explain the clonal differences in drought resistance. Root density and root density to stem volume ratio increased more in response to moderate drought in Clone DN than in Clone TD, resulting in enhanced drought resistance (high stem volume growth rate under moderate drought conditions) and an increased capacity to withdraw water from the soil. We conclude that the greater drought resistance of Clone DN compared with Clone TD was the result of the maintenance of a more favorable water balance by stomatal regulation and greater carbon allocation to roots during the early stages of drought. However, the low root density to stem volume ratio in Clone DN growing in the 46-cm irrigation treatment suggests that severe water limitation restricted the preferential allocation of carbon to belowground tissues, so that both root and shoot growth were constrained by severe drought.

Screening for Drought Resistance in Spring Chickpea in the Mediterranean Region*

AbstractEven though chickpea (Cicer arietinum L.) is well adapted to growing on stored soil moisture in drought‐prone environments, drought is a major yield reducer in most chickpea‐growing regions. Little progress has been made in breeding for improved performance under drought stress for want of a reliable and repeatable method of screening for drought resistance. Therefore, a study was initiated in 1990 to develop a screening technique and a rating scale to evaluate germplasm for drought resistance. A spring date‐of‐planting experiment was conducted during spring from 1990 to 1992 at Tel Hayda (northern Syria) to see if the expression of genotypic differences in drought resistance should be accentuated. Simultaneously, a rating scale was developed. Using the screening technique and rating scale, over 4000 germplasm lines were evaluated from 1992 to 1995. The resulting screening technique involves delayed sowing by 3 weeks during spring at a relatively dry site (long‐term average annual rainfall of 328 mm), preliminary evaluation of materials on a rating scale of 1–9 to discard susceptible lines, and final evaluation of promising lines under stress (drought) and non‐stress (supplemental irrigation) conditions, selecting drought‐resistant lines which perform well under both conditions. In the 1–9 rating scale that was developed: 1 = no yield reduction as compared to a non‐stress control and 9 = all plants dry without producing any seed. Using this technique, 19 lines out of 4165 lines screened were identified as drought resistant, producing over 1 t ha−1 seed yield under drought conditions while being able to yield over 2t h−1 under non‐stress conditions. Resistant lines are being used by national programs in the Mediterranean region and by ICARDA for developing drought‐ and disease‐resistant. high‐yielding cultivars.

Effects of arbuscular mycorrhizal fungi and drought stress on growth and nutrient uptake of two wheat genotypes differing in drought resistance

The effects of an arbuscular mycorrhizal (AM) fungus and drought stress on the growth, phosphorus, and micronutrient uptake of two wheat genotypes exhibiting differences in drought resistance were investigated. Plants were grown on a low P (4 mg kg–1 soil) silty clay (Typic Xerochrept) soil-sand mix. Mycorrhizal infection was higher under well-watered than under dry soil conditions and the drought-resistant genotype CR057 had a higher mycorrhizal colonization than the drought-sensitive genotype CR006. Total and root dry matter yields and total root length were higher in mycorrhizal than in nonmycorrhizal plants of both genotypes. CR057 had higher total dry matter but not root dry matter than CR006 plants. The enhancement in total dry matter due to AM inoculation was 42 and 39% under well-watered and 35 and 45% under water-stressed for CR057 and and CR006, respectively. For both genotypes, the contents of P, Zn, Cu, Mn, and Fe were higher in mycorrhizal than in nonmycorrhizal plants and higher under well-watered than under dry soil conditions. The enhancement of P, Zn, Cu, Mn, and Fe uptake due to AM inoculation was more pronounced in CR006 than in CR057, particularly under water-stressed conditions. Thus CR006 benefitted from AM infection more than the CR057 under dry soil conditions, despite the fact that CR057 roots were highly infected. It appears that CR006 is more dependent on AM symbiosis than CR057.

Effects of Timing of Drought Stress on Abscission and Dry Matter Partitioning of Short‐duration Pigeonpea

AbstractShoot dry mass partitioning and cumulative abscission of leaf, flowers and pods were determined for nine short‐duration pigeonpea genotypes grown with adequate soil moisture throughout growth (control), or subjected to water stress during the late vegetative and flowering (stress 1), flowering and early pod development (stress 2), or pod fill (stress 3) growth stages. The total cumulative dry mass of abscised plant parts was lower for determinate genotypes, but it increased to a greater extent under water stress than that for indeterminate genotypes, with stress 2 having the greatest and stress 3 die least effects. The dry mass contribution of pods to total abscission was ≤ 5%, and not signiflcantiy affected by water stress, while the contribution of leaves increased and mat of flowers decreased. Stress 3 had no significant effects on abscission dry mass totals or components. Reduction in shoot dry mass under water stress was most pronounced for genotypes in die early pod development stage, and the dry mass contribution of leaves generally decreased and that of pods increased under stress 1 and stress 2. With similar abscission levels, the shoot dry mass of genotype ICPL 151, was similar to, or greater than, that of hybrid ICPH 9, under stress 1 and stress 2, and the contribution of pods to shoot dry mass was lower for hybrid ICPH 9 under both stress treatments. Genotypic differences in drought resistance were likely due to differences in the leaf area maintenance during, and in the recovery of dry mass and pod production following, water stress periods.

Morphological responses of seedlings of four species of Salicaceae to drought

The riparian distribution patterns of floodplain species are affected by fluctuations in water level. Rapidly declining water levels in river banks during the growing period of plants can result in limited availability of water, particularly on coarse substrates. Differences in drought resistance among Salix alba, Salix triandra, Salix viminalis, and Populus nigra, four species dominating river banks along the River Rhine, could explain part of the riparian distribution patterns. Mortality and growth responses of seedlings grown under well-watered and dry conditions were studied in a greenhouse experiment. Drought-induced mortality was 0% in S. alba and P. nigra, 37.5% in S. triandra, and 62.5% in S. viminalis, which correlated with differences in water-loss characteristics of the species studied: S. triandra and S. viminalis had much higher transpiration rates under well-watered conditions than S. alba and P. nigra. Decreased shoot to root ratios were observed in all species after 3 weeks of drought. The increase after drought of the root length to leaf area ratio was greatest for P. nigra, indicating that this species has a relatively efficient water economy. Specific leaf areas of draughted plants decreased in S. alba and P. nigra, reflecting smaller transpiration areas. Drought also affected root distributions, resulting for all four species in deeper rooting and increased root length in deeper soil layers. Salix viminalis and S. triandra showed the greatest increase in root length in deep soil layers. We concluded that P. nigra is most resistant to drought followed by S. alba and then S. triandra and S. viminalis, and that these differences are reflected in the distribution patterns of these species observed on the banks of the River Rhine. Keywords: drought resistance, Salix, Populus, root distribution, transpiration, leaf conductance.

THE ECOLOGY OF ELEVATIONAL POSITIONS IN PLANTS: DROUGHT RESISTANCE IN FIVE MONTANE PINE SPECIES IN SOUTHEASTERN ARIZONA

We subjected seedlings of five pine species from the Chiricahua Mountains, Arizona to drought in the greenhouse to assess the relationships among elevational position, drought resistance, and biomass allocation. In comparison with upper elevation species, lower elevation species survived longer and experienced less depression of photosynthesis in response to the imposed drought. During the last week of the 29‐d drought, internal water potential decreased little in lower elevation species but dropped precipitously in upper elevation species. Thus, relative drought resistance and elevational position of these pines seem associated with the ability of seedlings to survive drought by maintaining favorable plant water potential. Lower elevation and more drought‐resistant species allocated less biomass to roots than did other species, a fact suggesting, contrary to assumptions of recent plant community models, that biomass allocation was unimportant in species differences in drought resistance.

Differences in drought resistance among 3 deciduous oak species grown in large boxes

Le but de ce travail etait d'expliquer les grandes differences de croissance et de deperissement observees en foret suite a des secheresses, entre le chene pedoncule (Quercus robur L) et le chene sessile (Q petraea Liebl). De plus, le chene rouge d'Amerique (Q rubra L) a ete compare aux 2 chenes indigenes. Les effets d'un deficit hydrique edaphique controle sur la croissance et les relations hydriques de jeunes plants de ces 3 especes, cultives dans de grandes cuves, ont ete etudies. Les plants etaient assez âges pour avoir pu developper des systemes racinaires normaux (.)

Germination and establishment of Sahelian rangeland species : II. Effects of water availability.

In order to understand the vegetation dynamics of Sahelian rangelands, the effects of water availability on germination were investigated under controlled conditions in climate rooms. Mixtures of seeds from species that occur in the same habitats but have different seed characteristics were exposed to different watering treatments. Responses to the treatments in the climate room were comparable to those observed in the field situation. However, induction time was generally some-what longer, and in some cases the germination rate was lower. The size, frequency, and timing of showers decisively influenced the ratio between the proportions of the various species among the seedlings that established. In general, conditions were favourable for fast germinating species with rainfall patterns without serious intermittent periods of drought, whereas the conditions became favourable for the slower germinating species after dry periods had eliminated the seedlings of the fast germinating species. Large differences in drought resistance were found among seedlings of different species. This causes more differentiation in establishment of species. Seed losses during the pre-emergence phase were also important. These losses can be very high, especially for the fastest germinating species. The dynamics observed in field situations could be explained on the basis of germination characteristics and drought resistance.

Accumulation of free amino acids in the shoots and roots of three northern conifers during drought.

The effects of drought on the free amino acid pools in 21- to 23-week-old seedlings of black spruce (Picea mariana (Mill.) Britt.), white spruce (Picea glauca (Moench.) Voss) and jack pine (Pinus banksiana Lamb.) were followed during soil drying. Although water and pressure potentials were sensitive to water deficits, large changes in osmotic potential were not recorded until after the development of severe drought. Total soluble amino nitrogen in the shoots and roots of the three species rose as turgor declined, with peak concentrations attained late in the drought period when the pressure potentials of the shoots approached zero. All white spruce seedlings were alive at zero turgor and showed large decrements in osmotic potential, but concentrations of free amino nitrogen in the roots and shoots showed only modest increases, reaching 125 to 150% of their control values. In contrast, large numbers of black spruce and jack pine were dead or severely damaged at zero turgor, and only small changes in osmotic potential were detected during soil drying. Nevertheless, concentrations of soluble amino nitrogen in both species reached 150 to 200% of control values a few days before the seedlings died. Alanine, arginine, aspartic acid/asparagine, glutamic acid/glutamine, glycine, hydroxyproline and proline were the major components of the free amino acid pools under both water-stressed and non-stressed conditions, with the largest and most consistent increases observed in the roots of all three conifers. Although proline was an important and dynamic component of the free pools, absolute concentrations were commony equalled or exceeded by other free amino acids in the roots and shoots and nearly always exceeded by the concentration of aspartic acid/asparagine in both tissues. Differences in drought resistance among the three conifers were not reflected by unique patterns of amino acid accumulation or by large differences in absolute concentrations of the free amino acid pools.

Comparative ecophysiology of Larix kaempferi (Lamb.) Carr. and Abies veitchii Lindl. 1. Seedling establishment on bare ground on Mt. Fuji

It is well known that plant species can establish themselves and grow only in a limited environment, known as the habitat. This indicates that each species lacks certain types of characteristics which enable it to become established beyond its habitat. By monitoring the fate of introduced seeds or transplants, some investigators have tried to ascertain the reasons why plants cannot become established outside their original habitats (Cavers and Harper, 1967; Gross and Werner, 1982; Goldberg, 1985; Barnes, 1985). Other workers have compared seedlings germinated in their own habitats with those germinated outside the habitat (Tobiessen and Werner, 1980). However, they have rarely succeeded in identifying the environmental factors and the plant characteristics directly responsible for the elimination of species from non-original habitats. An example of habitat segregation of saplings can be seen on Mt. Fuji at about 2300 m above sea level. Saplings of Larix kaempferi, a pioneer tree species, are relatively common on the bare ground. On the other hand, saplings of Abies veitchii, a seral species invading developed Larix forests (Nakamura, 1985), are found only rarely within the species groups invading bare ground. These facts indicate that A. veitchii lacks certain characteristics which enable it to become established on bare ground. The first of the present investigations was a sowing experiment on bare ground in the field, and the second was a pot experiment designed to detect any differences in drought resistance between the above two species. From the results of these two investigations, I concluded that the absence of A. veitchii from bare ground was due to its lower drought resistance.

Different strategies of drought resistance in three Mediterranean sclerophyllous trees growing in the same environmental conditions.

Measurements have been made of leaf conductance to water vapour, relative water content and water potential in Olea oleaster Hoffmgg et Link, Ceratonia siliqua L. and Laurus nobilis L., three evergreen sclerophyllous trees growing in Sicily at sea level. Measurements were made hourly in May and September 1986. Although all the three species are regarded as components of a homogeneous group (sclerophylls) and they all showed a high degree of sclerophylly, the strategies they adopted to withstand drought were completely different. Olea oleaster behaved as a 'drought-tolerating' species. Drought was 'avoided' by Ceratonia siliqua by a 'water-spending' strategy and by Laurus nobilis by a 'water-saving' strategy combined with the capability of recovering even minimal water losses by dropping leaf water potential drastically. Such differences in drought resistance are discussed in terms of differences in the bulk elastic modulus of leaf cells and wood anatomy.

Differences in Drought Resistance between Two Corn Hybrids. I. Water Relations and Root Length Density1

AbstractCorn (Zea mays L.) hybrids are often selected for near optimal conditions of water availability, yet frequently are grown under less than ideal soil moisture. Different responses among corn hybrids to drought stress have been observed, but the physiological and morphological differences that confer drought resistance or susceptibility are not well understood. The objective of this study was to identify differences in leaf water relations, stomatal activity, and root length density distribution between two corn hybrids known to differ in their response to water stress. During the 1983 and 1984 growing seasons, two corn hybrids (Pioneer Brands 3192 and 3165) were subjected to three water management treatments: irrigated, rainfed, and stress during vegetative (1983) or reproductive (1984) growth. During periods of water stress, hybrid 3192 wilted 2 to 3 days sooner and maintained leaf water potentials (ΨL) and leaf turgor potentials (Ψp) that were 0.2 to 0.5 MPa and 0.1 to 0.3 MPa lower, respectively, than those of hybrid 3165. Water stressed plants of hybrid 3192 closed their stomata earlier during periods of water stress, but the relationship between leaf diffusive resistance and Ψp was similar for both hybrids, with stomata beginning to close as Ψp decreased below 0.4 MPa. Regardless of the stage of ontogeny, hybrid 3165 always maintained a lower Ψp at a given ΨL than hybrid 3192. However, the primary difference observed between the two hybrids was the ability of hybrid 3165 to simply avoid tissue desiccation by maintaining higher ΨL and Ψp. The deeper rooting profile of hybrid 3165 may have contributed to the maintenance of higher ΨL and Ψp during water stress.

Differences in Drought Resistance between Two Corn Hybrids. II. Component Analysis and Growth Rates1

AbstractRelatively little research has been conducted to evaluate differing responses to water stress among genotypes of the same species. The objective of this study was to identify differences in growth and development of plant parts resulting from water stress imposed on two corn (Zea mays L.) hybrids that had been observed to differ in their sensitivity to water stress. During 1983 and 1984, two corn hybrids (Pioneer Brands 3192 and 3165) were subjected to three water management treatments: optimal irrigation, rainfed, and stress during vegetative (1983) or early reproductive (1984) growth. Growth analysis revealed few differences between hybrids for leaf area index, and crop and seed growth rates when well‐watered or stressed during vegetative growth, except that hybrid 3192 showed more rapid early growth. When well‐watered, grain yield of hybrid 3192 was the same (1983) or higher (1984) than grain yield of hybrid 3165. However, the two hybrids differed in their ability to resist severe water stress. The greater grain yield of hybrid 3165 in the rainfed treatment was associated with relatively smaller reductions in crop growth rate, total biomass accumulation, seed number, effective filling period, and harvest index with stress when compared to hybrid 3192. The greater crop growth rate and final biomass and grain yield of hybrid 3165 during severe stress most likely resulted from the maintenance of higher leaf water and turgor potentials and lower leaf diffusive resistances that were apparently mediated by higher root length densities in deeper zones of the soil profile as described in a companion paper.

生態型の異なるメロンの耐乾性の差異

生態型の異なるメロンの耐乾性の差異

Effect of temperature on drought resistance and growth of cotton plants

In cotton plants (Gossypium hirsutum L. cv. B.J.A.) the temperature of the roots affected both root and shoot growth, as did the temperature of the shoot. Drought resistance increased when the temperature imposed on roots (27°C) was lower than that imposed on shoots (17°C); the result was a decrease in both transpiration and flow of root sap. Stomatal characteristics as measured by density, index and resistance, depended only on shoot temperature. Differences in drought resistance, depended only on shoot temperature. Differences in drought resistance seem to be a result of changes in transpiration flow modulated by the amount of absorbed water.