The present work aims to study the drought stress effects on polyamine content and its relationship with growth and development in seeds, during cell division (from the beginning and until 17 days after pollination) and grain filling (until reaching the physiological maturity) stages. Factorial experiment based on Randomized Complete Block (RCB) design was carried out with three replications. Two factors of the experiment were considered: the level of irrigation (irrigation without and with drought stress during cell division stage and with drought stress during grain filling stage) and the level of wheat genotype (drought-resistant, semi-resistant and sensitive genotypes). As control treatment, soil moisture content of the field was considered. For drought-stress treatment, the 50% of the soil moisture content in control treatment was established. According to the experimental results, Putrescine content value is higher in control treatment which develops seeds of drought-resistant genotypes than that are registered for semi-resistant and sensitive genotypes. Both drought stress treatments induced significant rises in putrescine amount in the different genotypes of the study. The rises of putrescine content in sensitive and semi-resistant genotypes, however, were higher than in resistant ones, and the highest rise in putrescine content appeared in manning semi-resistant genotype during the stage of grain filling (27 days after pollination). Exerting drought stress in both stages of cell division and grain filling led to significant increase in spermine and spermidine contents of developing seeds of entire genotypes of the study. The highest spermidine content during grain filling stage occurred in sensitive genotypes of Shark and Tevee’s, and the lowest occurred in semi-resistant genotype of Sabalan. The highest spermine content during cell division stage, though, happened in semi-resistant genotype of manning. In fact, spermine and spermidine act as analogous to plant hormones such as Auxin and Cytokine, or they cooperate with these hormones in order to take a role in cell division regulation of developing wheat seeds and development of sink strength. They, additionally, stabilize the cell division process of developing seeds under drought condition. According to the findings of the study, manning semi-resistant genotype is capable of having a high grain yield under drought condition by reason of reserving high amounts of polyamines.
Drought, every year, jeopardizes the potential successful outcome of agricultural crops in Iran and many other countries around the world with varying degrees severity. Iran is located on the desert belt of the earth, and with the exception of some small regions in the vicinity of Caspian Sea coasts, Elburz and Zagros Mountains, the whole country has arid or semi-arid climate. Hence, drought stress is considered as one of the major threats of wheat production of the country, and owing to the recent lasting droughts, it has attracted much more attention.
According to Lie et al. [
One of the key elements which disrupts the growth and development of the plant under drought stress condition is producing reactive oxygen species in organelles such as mitochondrion, chloroplast and peroxisome [
In plants a great number of bio-chemical and physiological processes of molecules, tissues and organs, and eventually, the plant itself, play roles in the tolerance of drought stress condition. When a plant loses water under drought stress, for instance, its resistance is against that is shown by shutting the pores of the plant. In this situation, also the root system tries to absorb more water by taproots and fibrous roots [
Polyamines are hormone-like compounds whose concentration in plant cells is higher than the concentration of plant growth regulators such as abscisic acid (ABA), cytokinins (CK), auxins (IAA) and gibberellins (GA). Millimolar concentrations of polyamines are essential for producing biological response, and they are valuable polycations which take roles in different stages of plant growth and development. In fact, spermidine (Tri-amine), spermine (Tetra-amine) and their precursor, putrescine (Di-amine), are considered as the foremost polyamines. On the other hand, polyamines acts as growth regulators, are capable of intervening in numerous domain of growth and development processes such as cell division fertilization, embryogenesis, morphogenesis, root development, flowering process, fruit maturity, senescence delaying, membrane stability, stress tolerance and free radicals scavenging activity [
Plants resistance against non-biological stresses such as drought and salinity could be improved by using polyamines. This became a noteworthy topic in the past few years, and it has reported their function as oxygen free-radicals deactivators [
The present work aims to study the drought stress effects on polyamine content and its relationship with growth and development in seeds, during cell division (from the beginning and until 17 days after pollination) and grain filling (until reaching the physiological maturity) stages. Factorial experiment based in Randomized Complete Block (RCB) design was carried out with three replications. Two factors of the experiment were considered.
This work was carried out in Agriculture Department of Higher Education Center of Shahid Bakeri, Urmia University, Urmia, Iran.
A factorial experiment in Randomized Complete Block (RBC) design was carried out using 3 replications. Two factors were studied, the level of irrigation (irrigation without drought stress, with drought stress from the beginning of pollination until 17 days after, with drought stress from the day 17 after pollination until the physiological maturity) and the different genotypes (resistant genotypes of PTZ NISKA/UT1556-170//UNKNOWN, TRK13/KAUZ, Dogu88/Ghafghaz 7, Sardari HR-86, Daric 98-95 and ZHONG 25792; semi-resistant genotypes of Manning/Sdv1/Dogu8, Sabalan, Rasad and DH-2049-3; sensitive genotypes of SHARK and TEVEE'S'//CROW/VEE'S).
According to Ehdaie [
Soil analysis revealed that there was no need for phosphorus or potassium fertilizers. Only, nitrogen fertilizer required. Thus, 260 kg of urea was applied per hectare in three stages, planting, tillering and before flowering.
After the experiment (standard and stresses applied) spikes were randomly harvested and wheat grains were taken out using a forceps, wrapped in aluminum foil and placed in liquid nitrogen. Thereafter, samples were taken out from liquid nitrogen and kept at −70˚C.
The method employed by Ma [
50 - 100 μL of the solution was saturated by 200 μL of sodium carbonate, and mixed with 400 μL of dansyl chloride. Samples were vortexed and kept in dark at 60˚C. Then, 100 mg/L of proline was added. After 30 minutes, 500 μL of toluene was added and vortexed again. The organic phase formed was separated and drying in Liofilizar. The precipitates were vortexed in 1 mL of Ethanol and diluted 1 to 5.
High-Performance Liquid Chromatography (HPLC) with a C18 column was employed to measure organic compounds. For HPLC calibration, water and methanol were utilized as solvent. HPLC grade of 60 - 95 percent of methanol for the first 23 minutes, 100 percent in 23 - 28 and 60 percent of methanol from 28 until 32 with flow rate of 1 mL/min were operated. Fluorescence detector at excitation wavelength of 365 nm and emission wavelength of 510 nm was used. Subsequent, spermidine, spermine and putrescine were injected and area under every polyamine curve was calculated. Then, standard curve and the relationships between concentration and area under the curve were established.
Finally, for yield determination, 1 square meter was harvested from every plot after removing the margins in maturity stage of the crops. For component yields calculation including kernel per spike and 1000 kernels weight, randomly 10 bushes were selected as sample and the calculation done.
Statistical calculations were made using SPSS software (version 19), and mean comparisons were carried out using Duncan Method for a significance level of 0.05.
Variance analysis revealed that kernel per spike variance, 1000 kernels weight and grain yield characteristics of genotypes of the study have statistically significant differences at the 0.05 level. Drought stress treatment, in addition, had a significant effect on the kernel per spike, 1000 kernels weight and the grain yield characteristics at 0.05 level of significance (
The significant interaction effect between drought stress treatment and genotype on the grain yield ascertained that exerting experimental drought stress brings about a decrease in the grain yield of genotypes of the study. Comparing
S.O.V | df | Grain Yield | Grains per Spike | 1000 Grains Weight |
---|---|---|---|---|
Genotype | 11 | 11,556.41* | 160.20* | 386.08* |
Drought | 1 | 1,703,590.55* | 196.61* | 1950.47* |
Genotype × Drought | 11 | 8787.76* | 52.03* | 31.38* |
Error | 120 | 2.70 | 3.34 | 2.85 |
Variation Coefficient | - | 30.33 | 11.92 | 22.12 |
*Significant at 0.05 level. nsNot significant.
the means, additionally, displayed that the maximum and the minimum grain yield under drought stress condition belonged to genotypes of TEVEE’S’// CROW/VEE'S (173 g·m−2) and Manning/Sdv1/Dogu88 (221 g·m−2), respectively (
Comparing the mean of interaction effect between drought stress and genotype on kernel per spike characteristic revealed that the highest amount of kernel per spike belonged to genotype TRK (39/1), and the lowest amount under drought stress condition appeared in genotype Shark (28),
Emergence of drought stress after pollination induces drop in grain yield, which probably happens due to the drop in nutrient storage and the storage capacity of grains [
two yield component, i.e. kernel per spike and spike per area unit, by reason of not fulfilling the required photosynthetic substances of grains, and this drop in the yield component lead to much more drop in the grain yield [
Results from analysis of variance for spermidine characteristic revealed that there is significant difference at 0.05 level among genotype and drought stress treatments and their interaction (
There were dissimilar amounts for spermidine content of studied genotypes under drought stress after pollination. It was not observed any significant difference among drought-resistant genotypes (TRK, PTZ and Sardari) during the second and third phases of sampling, i.e. 17 and 27 days after pollination. There was a continuous and significant increase, however, in the spermidine contents of drought-sensitive genotypes.
The highest amount of spermidine content in the last phase of sampling (27 days after pollination) happened in drought-sensitive genotypes of Shark and Tevee’s, and the lowest Spermidine content belonged to semi-resistant genotype of Sabalan. Comparing the different phases of sampling revealed that there was a significant difference in the spermidine content of different genotypes. Additionally, results showed that under the typical irrigation condition, resistant and semi-resistant genotypes of the study had the lowest spermidine content and the sensitive-genotypes had the highest amount (
The higher concentration of spermidine during the growth of developing seeds in all genotypes of the study revealed a similar behavior to that of sper-
Spermidine | Spermine | Putrescine | Drought Stress | Genotypes |
---|---|---|---|---|
304 f | d8/22 | 321 c | Control | TRK |
712 a | a7/27 | 357 b | 17 days after pollination | |
748 a | c7/27 | a411 | 27 days after pollination | |
308 f | de5/21 | 316 c | Control | PTZ |
702 b | ab6/26 | 341 b | 17 days after pollination | |
732 a | d6/22 | 389 a | 27 days after pollination | |
312 f | d2/22 | 324 c | Control | Sardari |
721 a | a4/28 | 353 b | 17 days after pollination | |
740 a | bc7/24 | 393 a | 27 days after pollination | |
301 f | d4/22 | 307 d | Control | D/Gh |
663 c | b3/25 | 323 c | 17 days after pollination | |
702 b | c1/23 | 377 ab | 27 days after pollination | |
283 g | e7/20 | 297 d | Control | Daric |
603 d | b7/25 | 309 d | 17 days after pollination | |
673 c | de7/21 | 371 ab | 27 days after pollination | |
261 g | de2/21 | 274 e | Control | Zhong |
617 d | ab3/26 | 299 d | 17 days after pollination | |
681 b | 22/v c | 359 b | 27 days after pollination |
*Letters above the numbers indicate the significance of mean differences for a significance level of 0.01.
mine. Spermidine has a role in cell division of developing seeds as well. Moreover, the increase in the concentration of this polyamine under drought stress condition showed that spermidine might have influence on preserving the integrity and subcellular compartments as well as stabilizing the cell division process under drought stress, resembling the spermine.
Variance analysis of spermine characteristic led to believe that there is a significant difference at 0.05 level among main effects of drought stress, genotype and their interaction (
The results, furthermore, showed that the variability of spermine contents differed among the whole genotypes of the study. The highest amounts of spermine concentration in the whole genotypes of the study occurred in the cell division phase of the seeds (17 days after pollination), nevertheless, the amount of spermine concentration in manning semi-resistant genotype and resistant genotypes were significantly higher than in other genotypes. In summary, the highest spermine content which happened in 17 days after pollination belonged to manning semi-resistant genotype,
Ma [
The increase in spermine content of developing manning semi-resistant genotypes inhibited the decrease in grain yield by inhibiting the decrease in cell division and, subsequently, grain sink size. The increase in the spermine in cell division process of drought-resistant genotypes, however, was not sufficient to inhibit the decrease in grain sink size. Taking into consideration the role of poly- amines in preserving the viability and integrity of the membrane and subcellular compartments [
Variance analysis results for putrescine characteristic indicated that there is significant difference at 0.05 level among genotype and drought stress treatments and their interaction (
Contrasting the means gave the idea that putrescine content is dependent upon the intensity of stress and the genotype itself. There were found a significant difference among the genotypes under typical irrigation, and all the resistant genotypes, except Zhong genotypes, had the most putrescine contents. In the second phase of sampling (17 days after pollination), resistant genotypes of TRK, Sardari and Manning semi-resistant genotypes had the most putrescine content in comparison with the other genotypes. However, in the last phase of sampling (27 days after pollination) the most increase in putrescine content was observed in Manning semi-resistant genotype, and the rise in putrescine content of sensitive and semi-resistant genotypes was outstanding in comparison with resistant genotypes (
Assessing polyamine contents in resistant-genotypes which were under drought stress condition, after pollination, revealed that the stress induced continuous rise in all the polyamines (putrescine, spermidine and spermine),
Spermidine | Spermine | Putrescine | Drought Stress | Genotypes |
---|---|---|---|---|
374 d | 8/3 e | 147 e | Control | Rasad |
352 d | 13/3 d | 259 d | 17 days after pollination | |
639 b | 9/7 e | 483 b | 27 days after pollination | |
277 e | 9/2 e | 156 e | Control | Sabalan |
298 e | 14/8 d | 279 d | 17 days after pollination | |
564 c | 10/1 e | 492 b | 27 days after pollination | |
337 d | 20/4 c | 213 d | Control | Manning |
723 a | 29/3 a | 363 c | 17 days after pollination | |
757 a | 25/9 b | 583 a | 27 days after pollination | |
317 d | 9/7 e | 231 d | Control | DH |
389 d | 15/1 d | 309 c | 17 days after pollination | |
634 b | 10/5 e | 497 b | 27 days after pollination |
*Letters above the numbers indicate the significance of mean differences for a significance level of 0.01.
(
Substantial rise in spermidine content was observed in semi-resistant genotypes in comparison with other polyamines when the severity of drought stress was increased. The putrescine was the second while the lowest amount of polyamines was observed in spermine (
Continuous rise in the putrescine, spermine and spermidine content was observed in the drought-sensitive genotypes. The spermidine content was higher in comparison with putrescine and spermine, under both typical irrigation and drought stress conditions. The putrescine was second to the spermidine and the lowest amount of polyamines was observed in spermine.
This finding suggests that sensitive genotypes used in the study have a tendency to accumulate much more spermidine under harsh drought stress (
Spermidine | Spermine | Putrescine | Drought Stress | Genotypes |
---|---|---|---|---|
517 c | 11/6 c | 227 a | Control | Tevee’s |
741 b | 22/6 a | 238 b | 17 days after pollination | |
802 a | 18/3 b | 463 a | 27 days after pollination | |
534 c | 11/9 c | 233 b | Control | Shark |
739 b | 23/5 a | 247 b | 17 days after pollination | |
796 a | 18/3 b | 476 a | 27 days after pollination |
*Letters above the numbers indicate the significance of mean differences for a significance level of 0.01.
The findings of the study point out that sensitive and semi-resistant genotypes have small influence on putrescine metabolism and its transformation under drought stress into spermine and spermidine; consequently, the putrescine concentration in genotypes arises. Liu et al. measured the differences among putrescine concentration in leaves of the drought-sensitive and -tolerant wheat cultivars and noticed that under the drought stress condition, the putrescine concentration in the leaves of sensitive cultivars significantly increases in comparison with tolerant cultivars [
Other studies showed that variability in polyamine contents happens due to the reaction to various environmental stresses [
In 2007, Yang et al. studied 6 different rice cultivars with different drought tolerance in order to assess the effect of drought stress on polyamine content of the seeds [
The spermidine content in the resistant genotypes was increased much more than the increase in spermine and putrescine content. Researchers believe that the shortfall of putrescine content in resistant genotypes accounts for rapid transformation of the putrescine into other polyamines [
In this study, polyamines content of all genotypes which were studied under drought stress increased, and the highest increase in putrescine content under drought stress happened in semi-resistant genotypes. In addition, the highest increase in spermine content under the drought stress condition happened in resistant genotypes, and the highest increase in spermidine content happened in sensitive genotypes.
The increase in concentration of spermine and spermidine under the influence of drought stress condition during different grain development stages might be due to their effect on the viability of cell division and their unique role on stability of membrane, nucleic acids and other organelles.
The excess in the concentration of spermine and spermidine of manning genotype seeds under drought stress condition might inhibit the decrease in grain filling and bring about a delay in senescence of the plant via protecting cells, and subsequently, cause higher function of manning genotypes in comparison with other genotypes.
According to the study, semi-resistant genotype of manning seems to be capable of having high function under the drought stress condition by means of preserving high amounts of polyamine inside the seeds. Nevertheless, the amount of polyamines does not seem to be the sole main and determining factor of continuous function of manning in semi-resistant genotypes, and its role has to be taken under consideration with other physiological characteristics and has to be studied further and more accurately.
Seyedsalehi, M., Sharifi, P., Paladino, O., Hodaifa, G., Villegas, E.C. and Osman, R.M. (2017) Variation in Polyamine Content among 12 Pollinated Wheat Genotypes under Drought Stress Condition. Open Journal of Geology, 7, 1094- 1109. https://doi.org/10.4236/ojg.2017.78073