Endogenous Abscisic Acid Content Research Articles

Jasmonic acid, polyamine, and antioxidant levels in apple seedlings as affected by Ultraviolet-C irradiation

The effect of UV-C irradiation on jasmonates, abscisic acid (ABA), polyamines and antioxidant activities was investigated in apple plants (Malus domestica Borkh.). The EC50 values of O2 –-scavenging activity in the UV-C treated leaves were lower than those in the untreated control. In addition, total ascorbic acid and polyphenolic concentrations in the UV-C treated leaves were generally higher than those in the untreated control. Although the endogenous ABA concentrations were not significantly different between the untreated control and UV-C treatment, the endogenous jasmonic acid, putrescine, and spermine concentrations in the UV-C treated plants were higher than those in the untreated control. However, the application of PDJ before UV treatment inhibited the rise of endogenous jasmonate and putrescine concentrations. The increase of ascorbic acid was also inhibited by PDJ application before UV treatment. These facts suggest that the increase of jasmonates and polyamines may be associated with UV-C stimulation, and UV-C irradiation may be effective for increasing antioxidant activity in apple leaves.

Characterization of a single recessive yield trait mutant with elevated endogenous ABA concentration and deformed grains, spikelets and leaves

The characterization of yield trait mutants is important for understanding the regulation of grain yield formation in staple food crops. Meh0239 is a yield trait-related mutant identified from a mutant library of the common wheat cultivar Wangshuibai created by ethylmethyl sulfide (EMS) treatment of dry seeds. To shed some light on the nature of this mutation, it was investigated morphologically, physiologically, anatomically and genetically. The mutant plant showed obvious phenotypic differences in comparison with the wild type, starting at the seedling stage, including reduced plant height, wider and shorter leaves, shortened spikes, spikelets and grains and a more compact spikelet distribution. Also, seeds produced in the mutant germinated more slowly. Meh0239 contained a significantly higher level of abscisic acid (ABA) but lower levels of indole-3-acetic acid (IAA), methyl jasmonate (MeJA) and zeatin riboside (ZR) in flag leaves. Cells of all types in the leaf epidermis appeared shorter along the axial direction. The bulliform cells and long cells on the adaxial leaf surface were abnormal in shape. A genetic analysis using two F 2 segregating populations indicated that a single recessive mutation in wheat chromosome 7DS, about 3.1 cM distal from Xwmc506, caused these variations. Because of the pleiotropic nature of this gene and its relation with yield trait formation, we named it Yt1 for yield trait related 1.

Quantification of free and conjugated abscisic acid in five genotypes of barley ( Hordeum vulgare L.) under water stress conditions

The goal of the present study was to obtain new insights into the mechanisms underlying drought stress adaptations in barley plants. For this purpose we evaluated changes in endogenous abscisic acid (ABA) and its glucose ester conjugate (ABAGE), as well as changes in proline content, water relations and growth parameters of five barley genotypes with different drought resistance characteristics. Different responses among the five genotypes studied (Ardahoui, Pakistan, Rihane, Manel ad Roho) led to changes in their pattern of growth and development under drought conditions. Water stress induced a reduction in relative water content, as well as an increase in proline content and endogenous ABA concentrations in all tested genotypes. The lack of water led to a 2-fold increase in proline content for var. Rihane and to a 5-fold increase in endogenous ABA for cv. Ardhaoui. Also, increases in endogenous ABAGE in all genotypes except for cv. Ardhaoui were observed. Our results show that changes in ABA and ABAGE correlated with variations in proline content and growth parameters of these genotypes which present different mechanisms to cope with water stress. We also suggest that new regulatory mechanisms implying ABA mobilization can be of great importance in adaptation of barley to drought.

Cloning and expression analysis of cDNAs for ABA 8′-hydroxylase during sweet cherry fruit maturation and under stress conditions

Abscisic acid (ABA) plays a key role in various aspects of plant growth and development, including adaptation to environmental stress and fruit maturation in sweet cherry fruit. In higher plants, the level of ABA is determined by synthesis and catabolism. In order to gain insight into ABA synthesis and catabolism in sweet cherry fruit during maturation and under stress conditions, four cDNAs of PacCYP707A1 — PacCYP707A4 for 8′-hydroxylase, a key enzyme in the oxidative catabolism of ABA, and one cDNA of PacNCED1 for 9-cis-epoxycarotenoid dioxygenase, a key enzyme in the ABA biosynthetic pathway, were isolated from sweet cherry fruit ( Prunus avium L.). The timing and pattern of PacNCED1 expression was coincident with that of ABA accumulation, which was correlated to maturation of sweet cherry fruit. All four PacCYP707As were expressed at varying intensities throughout fruit development and appeared to play overlapping roles in ABA catabolism throughout sweet cherry fruit development. The application of ABA enhanced the expression of PacCYP707A1 — PacCYP707A3 as well as PacNCED1, but downregulated the PacCYP707A4 transcript level. Expressions of PacCYP707A1, PacCYP707A3 and PacNCED1 were strongly increased by water stress. No significant differences in PacCYP707A2 and PacCYP707A4 expression were observed between dehydrated and control fruits. The results suggest that endogenous ABA content is modulated by a dynamic balance between biosynthesis and catabolism, which are regulated by PacNCED1 and PacCYP707As transcripts, respectively, during fruit maturation and under stress conditions.

Effect of brassinosteroids on drought resistance and abscisic acid concentration in tomato under water stress

The effect of brassinosteroid (BR) on relative water content (RWC), stomatal conductance (g s), net photosynthetic rate ( PN), intercellular CO 2 concentration (Ci), lipid peroxidation level, activities of antioxidant enzymes and abscisic acid concentration (ABA) in tomato ( Lycopersicon esculentum) seedlings under water stress was investigated. Two tomato genotypes, Mill. cv. Ailsa Craig (AC) and its ABA-deficient mutant notabilis ( not), were used. Water stress was achieved by withholding water and both the AC and not plants were treated with 1 μM 24-epibrassinolide (EBR) or distilled water as a control. The RWC, g s, Ci and PN were significantly decreased under water stress. However, EBR treatment significantly alleviated water stress and increased the RWC and PN. EBR application also markedly increased the activities of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide dismutase) while it decreased g s, Ci and the contents of H 2O 2 and malondialdehyde (MDA). Interestingly, ABA concentration in AC and not plants was markedly elevated after EBR treatment although the increasing rate and amplitude of ABA in not plants treated by EBR was significantly lower than those in AC plants. Our study suggested that amelioration of the drought stress of tomato seedlings may be caused by EBR-induced elevation of endogenous ABA concentration and/or the activities of antioxidant enzymes.

Exogenous Gibberellic Acid Reprograms Soybean to Higher Growth and Salt Stress Tolerance

The agricultural industry is severely affected by salinity due to its high magnitude of adverse impacts and worldwide distribution. We observed the role of exogenous gibberellic acid (GA(3)) in salinity alleviation of soybean. We found that GA(3) application significantly promoted plant length and plant fresh/dry biomass while markedly hindered by NaCl induced salt stress. The adverse effect of salt stress was mitigated by GA(3), as growth attributes significantly recovered, when GA(3) was added to salt stressed soybean plants. Elevated GA(3) treatments increased daidzein and genistein contents (commonly known as phytoestrogens) of soybean leaves under control and salt stress conditions. Phytohormonal analysis of soybean showed that the level of bioactive gibberellins (GA(1) and GA(4)) and jasmonic acid increased in GA(3) treated plants, while the endogenous abscisic acid and salicylic acid contents declined under the same treatment. GA(3) mitigated the adverse effects of salt stress by regulating the level of phytohormones, thus aiding the plant in resuming its normal growth and development. The presence of GA(1) and GA(4) showed that both early-C13-hydroxylation and non-C13-hydroxylation pathways of GA biosynthesis are functional in soybean. It was concluded that GA(3) ameliorates the adverse effects of salt stress and restores normal growth and development of soybean.

Effect of abscisic acid on symbiotic nitrogen fixation activity in the root nodules of Lotus japonicus

The phytohormone abscisic acid (ABA) is known to be a negative regulator of legume root nodule formation. By screening Lotus japonicus seedlings for survival on an agar medium containing 70 μM ABA, we obtained mutants that not only showed increased root nodule number, but also enhanced nitrogen fixation. The mutant was designated enf1 (enhanced nitrogen fixation 1) and was confirmed to be monogenic and incompletely dominant. In long-term growth experiments with M. loti, although some yield parameters were the same for both enf1 and wild-type plants, both the dry weight and N content of 100 seeds and entire enf1 plants were significantly larger compared than those traits in wild-type seeds and plants. The augmentation of the weight and N content of the enf1 plants most likely reflects the increased N supplied by the additional enf1 nodules and the concomitant increase in N fixation activity. We determined that the endogenous ABA concentration and the sensitivity to ABA of enf1 were lower than that of wild-type seedlings. When wild-type plants were treated with abamine, a specific inhibitor of 9-cis-epoxycarotenoid dioxygenase (NCED), which results in reduced ABA content, the N fixation activity of abamine-treated plants was elevated to the same levels as enf1. We also determined that production of nitric oxide (NO) in enf1 nodules was decreased. We conclude that endogenous ABA concentration not only regulates nodulation, but also nitrogen fixation activity by decreasing NO production in nodules.

Effect of silicon on growth and salinity stress of soybean plant grown under hydroponic system

Silicon (Si) is abundant in the soil, yet its role in plant biology has been poorly understood. The role of Si in soybean growth and its effectiveness in salt stress alleviation was investigated. Sodium metasilicate (Na2SiO3) was given as Si source to hydroponically grown soybean (Glycine max (L.) Merr.). The plant growth attributes, i.e. plant height, plant fresh and dry biomass, chlorophyll contents and endogenous gibberellins (GAs) level improved with 2.5 mM Si, while endogenous abscisic acid (ABA) and free proline contents were not affected as compared to control. Sodium chloride (NaCl) significantly decreased growth attributes and endogenous gibberellins levels but markedly enhanced ABA and proline contents of soybean leaves. An addition of Si to salt stressed plants substantially alleviated the adverse effects of NaCl on growth, as it enhanced endogenous gibberellins, while reduced the levels of ABA and proline. GAs analysis of soybean leaves also showed that both early C13 hydroxylation and non C13 hydroxylation pathways of gibberellin biosynthesis were operating in soybean. The major GA biosynthesis pathway was identified as non C13 hydroxylation, which led to the formation of bioactive GA4. Current study suggests that Si application alleviates the detrimental effect of salinity stress on growth and development of soybean.

Shade and Plant Location Effects on Germination and Hormone Content of Palmer Amaranth (Amaranthus palmeri) Seed

Experiments were conducted to investigate the effects of shading on and location of the mother plant on germination and hormone content of Palmer amaranth seed. Increasing the shading from 0 to 87% decreased germination of fresh, viable seeds in dark from 25 to 12%. Abscisic acid (ABA) content of seeds from plants in 0% shade increased from 13.3 ng g−1dry seed to 19.1 ng g−1dry seed with 87% shade. Shading of the mother plant did not influence the 1,000-seed weight of Palmer amaranth. Seeds that matured in the top and middle third of the mother plant had 67 to 78% greater germination than those that matured in the bottom third of the mother plant. Endogenous gibberellic acid (GA) content of seeds did not differ between locations on the mother plant; however, the ABA content of seeds produced on the bottom third of the plant was 46 and 59% higher than the ABA content of seeds produced at the middle and top third of the plant, respectively. Endogenous ABA or GA content of seeds and 1,000-seed weight had no relationship with seed germination over and above the treatment effects. This research suggests that shading and plant location can influence germination of fresh, viable seeds of Palmer amaranth, which will be a dormancy strategy for seed dispersal over time.

The accumulation and transport of abscisic acid insoybean (Glycine max L.) under aluminum stress

Abscisic acid (ABA) plays an important role in mediating some biotic and abiotic stresses. In the present study, to better understand the relationship of ABA production and Aluminum (Al)-resistance in plants, Al-resistance genotype (Jiyu70) of soybean was adopted to investigate the accumulation and transport of ABA in plants exposed to Al. Results showed that exogenous application of ABA and ABA synthesis inhibitor-fluridone respectively increased and reduced endogenous ABA content in root apices of soybean, and results in the corresponding reduction and aggravation of Al toxicity. Increasing of either Al concentration (0–50 μM) or treatment duration (0–12 h, 30 μM Al) cause a higher inhibition of root elongation and ABA accumulation in root apices of soybean. Al-induced enhancement of endogenous ABA production not only was in roots but also in leaves, whereas La3+ (behaves similarly as Al3+ at the level of cell surface) only increased ABA accumulation in roots. In split-root experiments, Al treatment in two parts of roots (Part A, + Al; Part B, + Al) both decreased root elongation and increased ABA accumulation in root apices of soybean. Whereas when only part A of roots was exposed to Al (Part A, + Al; Part B, -Al), endogenous ABA content in root apices increased in part A but inversely in part B, but root elongation inhibition only was found in part A. Using [3H]-ABA radioisotope technique, it was found that [3H]-ABA can transport at the rate of more than 3.2 cm·min−1 in the whole plants, and this can be accelerated by Al supply. In addition, [3H]-ABA tended to distribute in the root part under Al stress. Together, these results suggest that ABA may play an important role in regulating Al resistance of soybean as an Al-stress signal.

Enhanced nodulation and nitrogen fixation in the abscisic acid low-sensitive mutant enhanced nitrogen fixation1 of Lotus japonicus.

The phytohormone abscisic acid (ABA) is known to be a negative regulator of legume root nodule formation. By screening Lotus japonicus seedlings for survival on an agar medium containing 70 microM ABA, we obtained mutants that not only showed increased root nodule number but also enhanced nitrogen fixation. The mutant was designated enhanced nitrogen fixation1 (enf1) and was confirmed to be monogenic and incompletely dominant. The low sensitivity to ABA phenotype was thought to result from either a decrease in the concentration of the plant's endogenous ABA or from a disruption in ABA signaling. We determined that the endogenous ABA concentration of enf1 was lower than that of wild-type seedlings, and furthermore, when wild-type plants were treated with abamine, a specific inhibitor of 9-cis-epoxycarotenoid dioxygenase, which results in reduced ABA content, the nitrogen fixation activity of abamine-treated plants was elevated to the same levels as enf1. We also determined that production of nitric oxide in enf1 nodules was decreased. We conclude that endogenous ABA concentration not only regulates nodulation but also nitrogen fixation activity by decreasing nitric oxide production in nodules.

Development of Drought‐Tolerant Canola (Brassica napus L.) through Genetic Modulation of ABA‐mediated Stomatal Responses

ABSTRACTCanola is one of the most important oilseed crops, and its seed yield and quality are significantly affected by environmental stresses such as drought. The phytohormone abscisic acid (ABA) is induced by drought and triggers stomatal closure to reduce transpiration, which accounts for >90% of water loss in plants. The ABA‐mediated stomatal response is a dosage‐dependent process that can be achieved by either increasing the endogenous ABA concentration or by sensitizing the responsiveness of guard cells to the hormone. We summarize the recent breakthroughs in the understanding of key molecular components that regulate the homeostasis and sensing of ABA, and their potential applications in genetic engineering for drought tolerant canola. In particular, the α and β subunits of protein farnesyltransferase have been identified as negative regulators of ABA‐mediated stomatal responses, and their effectiveness as the targets for engineering drought tolerance and yield protection has been confirmed in canola in the field. Further development of the drought stress tolerance property in the crop will likely have a fundamental impact on its productivity in many regions of the world.

Abscisic acid and 3-indolacetic acid levels during the reinvigoration process of Pinus radiata D. Don adult material

The maturation and phase change processes in woody species have not been completely clarified, specially the role of growth regulators during the maturation phase. Understanding their role better will allow to comprehend the physiological aspects of the species, which would allow to chose the optimal management conditions in forestry programs and make them more useful. In the present study, the endogenous content of abscisic acid (ABA) and 3-indolacetic acid (IAA) were quantified by high performance liquid chromatography, in the reinvigoration process of elite Pinus radiata material, during the development of homomicrografts (P. radiata/P. radiata) and heteromicrografts (P. radiata/Pinus caribaea), developed under in vitro conditions. The results showed an increase in the endogenous content of ABA through time and a decrease in the content of IAA. Significant differences were found in the endogenous content of ABA, where the maximum values were detected at 120 days of micrograft culture, being similar to the values obtained in juvenile buds. As well, significant differences were also detected in the endogenous content of IAA in the micrografted buds during all the development phases, compared with adult buds. However, no significant differences were detected in the endogenous content of ABA and IAA, regarding the type of rootstock employed. Considering the endogenous content of ABA and IAA, the micrografted plant material would be equal to the juvenile buds, since statistically they were equal to these buds, considering that the values obtained in this case are independent from the type of rootstock used.

The Role of Abscisic Acid in the Response of Two Different Wheat Varieties to Water Deficit

The changes in plant growth, transpiration rate, photosynthetic activity, plant pigments, electrolyte leakage, H2O2 content, lipid peroxidation, catalase activity and endogenous content of abscisic acid (ABA) were followed in the leaves of two wheat varieties (sakha 93 and 94) during drought stress and subsequent rehydration. Drought stress caused several inhibitory changes in the growth of both wheat varieties, particularly in sakha 94. Exogenous ABA treatment improved the growth of sakha 93 plants as indicated by a higher relative water content, transpiration rate and lower electrolyte leakage and also enhanced the growth during the recovery period. Such improvement may be the result of the induction of enzymatic (catalase) and non-enzymatic (carotenoid) systems. ABA treatment did not ameliorate the negative effect of drought on the growth of sakha 94.

Methyl jasmonate alleviated salinity stress in soybean

We studied the role of methyl jasmonate (MeJA) in alleviating NaCl-induced salt stress on soybean growth and development in hydroponics medium. Soybean seedlings were exposed to 60 mM NaCl stress for 2 weeks, 24 h after the application of 20 and 30 µM MeJA. NaCl stress induced a significant reduction in plant growth, endogenous bioactive gibberellin (GA4), photosynthesis and transpiration rate, while a marked increase in the endogenous abscisic acid (ABA) and proline contents were recorded. MeJA application greatly mitigated the adverse effects of NaCl on soybean growth and endogenous hormones. MeJA significantly increased ABA levels, while the endogenous amount of GA4 was reduced by the application of NaCl. Our study revealed that MeJA counteracted the negative effects of NaCl stress on plant growth, chlorophyll content, leaf photosynthetic rate, leaf transpiration rate, and proline content.

Effect of abscisic acid on photosynthetic parameters during ex vitro transfer of micropropagated tobacco plantlets

The aim of this research was to determine whether exogenous abscisic acid (ABA) applied immediately after ex vitro transfer of in vitro grown plants can improve their acclimatization. Tobacco (Nicotiana tabacum L.) plantlets were transferred into pots with Perlite initially moistened either by water or 50 µM ABA solution and they were grown under low (LI) or high (HI) irradiance of 150 and 700 µmol m-2 s-1, respectively. Endogenous content of ABA in tobacco leaves increased considerably after ABA application and even more in plants grown under HI. Stomatal conductance, transpiration rate and net photosynthetic rate decreased considerably 1 d after ex vitro transfer and increased thereafter. The gas exchange parameters were further decreased by ABA application and so wilting of these plants was limited. Chlorophyll (a+b) and β-carotene contents were higher in ABA-treated plants, but the content of xanthophyll cycle pigments was not increased. However, the degree of xanthophyll cycle pigments deepoxidation was decreased what also suggested less stress in ABA-treated plants. No dramatic changes in most chlorophyll a fluorescence parameters after ex vitro transfer suggested that the plants did not suffer from restriction of electron transport or photosystem damage.

Abscisic acid (ABA) inhibition of lateral root formation involves endogenous ABA biosynthesis in Arachis hypogaea L.

ABA has been found to play a significant role in post-embryonic developmental in peanut seedlings. The results from the current study indicate that in the presence of exogenous 10 μmol l−1 ABA, lateral roots (LRs) number decreased and seedling development was delayed. This effect was eliminated by 25 μmol l−1 naproxen, an inhibitor of ABA biosynthesis. The Arabidopsis mutant deficient in ABA biosynthesis, nced3, displays a phenotype with more and longer LRs. We found that ABA decreased root-branching in peanut in a dose-dependent way. ABA-treated seedlings showed higher endogenous ABA levels than the control and naproxen-treated seedlings. RT-PCR results indicated that the expression of AhNCED1, a key gene in the ABA biosynthetic pathway, was significantly up-regulated by exogenous ABA in peanut. The mRNA levels of AhNCED1 began to increase 2 days after ABA treatment. The results from the current study show that ABA inhibits peanut LR development by increasing endogenous ABA contents.

Enhanced determination of abscisic acid (ABA) and abscisic acid glucose ester (ABA-GE) in Cistus albidus plants by liquid chromatography–mass spectrometry in tandem mode

An improved, quick and simple method for the extraction and quantification of the phytohormones (+)-abscisic acid (ABA) and its major glucose conjugate, abscisic acid glucose ester (ABA-GE) in plant samples is described. The method includes the addition of deuterium-labeled internal standards to the leaves at the beginning of the extraction for quantification, a simple extraction/centrifugation process and the injection into the liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) system in multiple reaction monitoring mode (MRM). Quality parameters of the method (detection limits, repeatability, reproducibility and linearity) have been studied. The objective of this work is to show the applicability of this method for quantifying the endogenous content of both ABA and ABA-GE in Cistus albidus plants that have been grown during an annual cycle under Mediterranean field conditions. Leaf samples from winter plants have low levels of ABA which increase in spring and summer showing two peaks that corresponded to April and August. These increases are coincident with the high temperature and solar radiation and the low RWC and RH registered along the year. On the other hand, the endogenous levels of ABA-GE increase until maximum values in July just before the ABA content reaches its highest concentration, decreasing in August and during autumn and winter. Our results suggest that the method is useful for quantifying both compounds in this plant material and represents the advantage of a short-time sample preparation with a high accuracy and viability.

Differences in growth and physiological traits of Populus cathayana populations as affected by enhanced UV-B radiation and exogenous ABA

During one growing season, the effects of enhanced ultraviolet-B (UV-B) radiation, exogenous abscisic acid (ABA) and their combination on biomass accumulation, gas exchange, endogenous ABA, the concentration of UV-absorbing compounds, antioxidant system and on the carbon (C) and nitrogen (N) content and C/N ratio were investigated in two contrasting Populus cathayana Rehd. populations, originating from high and low altitudes in south-west China. Exogenous ABA was sprayed to the leaves, and enhanced UV-B treatments were applied using a square-wave system to expose the seedlings to ambient (1×) or twice ambient (2×) doses of biologically effective UV-B radiation (UV-B BE). Enhanced UV-B radiation significantly decreased height, basal diameter, total leaf area, total biomass, net CO 2 assimilation rate ( A), stomatal conductance ( g s ), transpiration rate ( E) and carbon (C) content in leaves, and significantly increased the activities of superoxide dismutase (SOD) and guaiacol peroxidase (GPx), and the contents of hydrogen peroxide (H 2O 2) and malonaldehyde (MDA), as well as the accumulation of UV-absorbing compounds and endogenous ABA concentrations among different organs in both populations. In contrast, exogenous ABA induced a significant decrease in A and significant increases in the activities of SOD and GPx, in the content of H 2O 2 and MDA, and in the endogenous ABA concentrations. Compared with the low altitude population, the high altitude population was more tolerant to enhanced UV-B and exogenous ABA. Significant interactions between UV-B and ABA were observed in A, E, and in the activities of SOD and GPx, as well as in endogenous ABA in the leaves and roots of both populations. Across all treatments, the C and N contents of leaves were strongly correlated with their contents in stems and roots. Additionally, the N content of leaves and stems were significantly correlated with the C content of stems.

Vivipary as a tool to analyze late embryogenic events in maize

In maize vivipary, the precocious germination of the seed while still attached to the ear, is the diagnostic phenotype of mutants, which are impaired in the biosynthesis or response to abscisic acid (ABA). Of the 15 genes so far described, 12 control specific steps in ABA biosynthesis, two mediate hormone response and one still has an undefined role. We have analyzed a collection of 25 independent vp isolates with the aim of determining the degree of mutational saturation that has so far been reached. Of the 25 viviparous mutants complementation tested, 22 correspond to known loci: six are allelic to vp1, another six to vp5, one to vp7, two to vp9, six to vp10 and one to w3. The remaining three represent genes not previously identified. All mutants so far tested except rea show a decrease in ABA content. As to the only two mutants (vp1 and rea) whose endogenous ABA content is not impaired, the reduction in sensitivity of the double mutant compared to the single ones suggests that the two genes control separate pathways in the ABA signal transduction. Some of the mutants in this collection have a characteristic incomplete germination that allows the embryo of the mature dry seed to resume germination. By exploiting this feature it is possible to infer, through a germination test, whether the mutant has been impaired in the acquisition of desiccation tolerance. This information provides the starting point for the dissection of the genetic basis of desiccation tolerance.