Induction of drought tolerance in cucumber plants by the application of mineral nutrient and plant growth regulator | |
| Author | Alam, Md. Akhter Ul |
| Call Number | AIT Diss no.AS-23-03 |
| Subject(s) | Plants--Drought tolerance Plants--Effect of drought on Water in agriculture Cucumbers |
| Note | A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Agricultural Systems and Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Cucumber, a popular vegetable crop of economic importance, is widely cultivated under greenhouse and open-field conditions and is consumed across the globe due to its high nutritional value. It is a rich source of minerals, vitamins, and antioxidants. However, the growth and development of cucumber plants are highly susceptible to soil moisture depletion as the plants have shallow root systems with around 85% of the root length confined in the top 30 cm of soil. Like other Cucurbits, cucumber has a high transpiration rate and requires high soil moisture during its lifetime; therefore, drought stress is a limiting factor for its growth and fruit yield. Cucumber demands more water than cereal crops. The pollination stage and fruit development stage of cucumber are the most sensitive growth stages to drought stress. Being a high water-demanding crop, especially at germination, seedling stage, and fruit development stage, the rising water scarcity poses a serious threat for cucumber production. Drought stress has emerged as a major issue impeding plant growth and development. The problem is further exacerbated by climate change, which has multifaceted impacts in the form of rising average surface temperature, a shift in rainfall pattern, and a variety of other natural calamities. The high susceptibility of cucumber plants to drought stress demands management strategies to maintain or enhance its yield under water-scarce conditions. To increase crop resilience toward drought stress and maximize crop yield and water productivity for ensuring sustainable cucumber production, application of innovative agronomic management practices (nutrient management) along with plant biostimulant (phytohormone) and an adoption of efficient water management strategy need to be integrated with existing cultivation practices. Therefore, through several laboratory and polyhouse studies, an interacting effect among nutrient management practice, plant biostimulant application, and irrigation regime was investigated on cucumber.In the first polyhouse experiment, the effect of six priming treatments (non-primed control, hydropriming, and priming with potassium nitrate [KNO3], dipotassium phosphate [K2HPO4], gibberellic acid [GA3], and salicylic acid [SA]) was assessed on cucumber under four soil moisture regimes (40%, 60%, 80%, and 100% field capacity [FC]). Decreasing soil moisture level from 100 to 40% FC caused a 37–48% reduction in shoot dry matter, 30–51% reduction in fruit weight, 77–84% reduction in fruit yield, 41–48% reduction in membrane stability index, and 30–119% increase in electrolyte leakage across seed priming treatments. Seed priming improved all evaluated germination, morphological, fruit yield and quality, and physio-biochemical traits, where KNO3 was the most effective priming material, which caused more than three fold increase in fruit yield and irrigation water productivity compared with the non primed plants. Physio-biochemical performance in terms of free proline concentration, net photosynthetic rate, stomatal conductance, and transpiration rate was also enhanced in the KNO3-primed plants in comparison to the non-primed plants regardless of soil moisture regimes. The results imply that priming of cucumber seeds, especially with KNO3, protects plants against water loss and increases their dehydration tolerance. Seed priming with KNO3 could be recommended for cucumber production under limited soil moisture availability.In the second laboratory and polyhouse experiments, the effect of five doses of salicylic acid (SA) (0 [control], 0.25, 0.50, 0.75, and 1.00 mM) either as a seed priming material (in laboratory study and experiment 1 in the polyhouse) or as a foliar spray (experiment 2 in the polyhouse) was evaluated on cucumber under four soil moisture regimes (40%, 60%, 80%, and 100% FC). Throughout the crop growing period, a portable soil moisture meter was used to regularly monitor soil moisture regimes for maintaining the appropriate FC levels. The effect of decreasing soil moisture was evident on all evaluated parameters and caused up to 84% reduction in fruit yield at 40% FC compared with that at 100% FC in both polyhouse experiments. A consistent trend of better results with 0.75 mM dose of SA regardless of application methods or crop growth stages was observed, which resulted in a significant increase in all germination parameters, growth, and fruit yield, as well as physiological traits. The same dose (0.75 mM) caused an increase of 19–69% and 31–69% in shoot dry matter in comparison to the control plants across soil moisture regimes applied as a seed priming material and foliar spray, respectively. More than three-fold increase in fruit yield and water productivity was observed for this dose at 60% FC in both polyhouse experiments in comparison to the control plants. Compared with the control plants, the same dose also caused a significant increase in leaf relative water content and membrane stability index irrespective of application methods or soil moisture regimes. The highest dose of 1.00 mM largely remained ineffective and the same was also generally true for the other doses applied in the present studies. Application of SA at 0.75 mM is recommended either as a seed priming material or foliar spray to grow cucumber in drought-prone areas.In the third polyhouse experiment, two independent experiments were conducted where cucumber plants were grown under four soil moisture regimes (40%, 60%, 80%, and 100% FC) and silicon (Si) was applied either as a seed priming material (Experiment 1) or as a soil drench (Experiment 2). For the seed priming study, four doses of Si (in the form of monosilicic acid with 20% Si content) applied were 0.25, 0.5, 1.0, and 2.0 mM along with a control in which seeds were directly sown without any priming. For the soil application study, four doses of Si (in the form of monosilicic acid with 20% Si content) applied were 15, 30, 60, and 120 kg ha–1 along with a control. Data on growth, fruit yield parameters, irrigation water productivity, and physio-biochemical parameters were collected. The lowest soil moisture regime of 40% FC resulted in 55–68% and 53–76% reduction in root dry matter in Experiment 1 and Experiment 2, respectively, compared with that at 100% FC across Si doses. Fruit yield, irrigation water productivity, and net photosynthetic rate exhibited a respective reduction of 77–84% and 78–84%, 25–52% and 13–47%, and 37–46% and 26–33% in Experiment 1 and Experiment 2, respectively, at 40% FC compared with those at 100% FC across Si doses. The exogenous application of Si was equally effective regardless of application methods. Seed priming dose of 0.5 mM outperformed other doses and resulted in an increase of 199–284%, 169–263%, and 20–59% in fruit yield, irrigation water productivity, and net photosynthetic rate, respectively, compared with the control across soil moisture regimes. Among different soil application doses of Si, 60 kg ha–1 was the most effective, which resulted in 217–293%, 198–307%, and 11–33% increase in fruit yield, irrigation water productivity, and net photosynthetic rate, respectively, compared with the control across soil moisture regimes. Application of Si at 0.5 mM as a seed priming material and 60 kg ha–1 as a soil drench is recommended to grow cucumber in drought-prone areas. |
| Year | 2023 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural Systems and Engineering (ASE) |
| Chairperson(s) | Datta, Avishek;Himanshu, Sushil Kumar (Co-Chairperson); |
| Examination Committee(s) | Salin, Krishna R.;Zulfiqar, Farhad; |
| Scholarship Donor(s) | Bangabandhu Science and Technology Fellowship Trust, Bangladesh; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2023 |