VIETNAM NATIONAL UNIVERSITY OF AGRICULTUREFACULTY OF AGRONOMY UNDERGRADUATE THESIS TITLE: EFFECT OF SALT STRESS AND DROUGHT STRESS ON GROWTH OF SUGAR CANE PLANTS UNDER GREENHOUSE CONDITI
INTRODUCTION
Introduction
Sugarcane (Saccharum officinarum) is a vital perennial grass from the Poaceae family, primarily cultivated in tropical and subtropical regions for sugar production With heights ranging from two to six meters, sugarcane features stout, jointed, fibrous stalks that accumulate sucrose in their internodes In 2017, it was the world's largest crop by production, yielding 1.8 billion tonnes, with Brazil contributing 40% of this total The Food and Agriculture Organization estimated that sugarcane was grown on approximately 26 million hectares across more than 90 countries in 2012 In Vietnam, sugarcane is economically significant, cultivated in regions like Thanh Hoa and Nghe An, and is poised to enhance productivity to meet domestic and export sugar demands, thus generating substantial foreign currency Currently, sugarcane plays a crucial role in transforming agricultural practices, boosting economic efficiency, and improving the ecological environment.
Drought is a critical abiotic factor that significantly impacts plant growth, development, and agricultural productivity worldwide It leads to reduced output and economic challenges for many nations To combat increasing drought conditions, it is essential to develop effective irrigation systems, implement zoning for water management, and utilize drought-resistant cultivars Specifically, drought adversely affects the productivity and yield of sugarcane, particularly in regions like Vietnam However, there is a lack of targeted research on the effects of artificial drought conditions on the growth and development of commonly cultivated sugarcane varieties.
Salinity is another one vital limiting factor for sus-tainable agriculture with depressing crop growth and production worldwide (Zinselmeier C,
Salinity affects over 6% of the world's land, impacting more than 70 countries (Amini, 2017) This stress not only diminishes crop yields by hindering leaf physiological growth (Starvridou, 2015) but also impairs plant roots' ability to absorb water and nutrients, such as nitrogen (Munns, 2017) Although some research indicates that salinity can enhance the growth and yield of transgenic barley in both greenhouse and field settings, the underlying mechanisms remain unclear (Schilling, 2014).
Following the fact mentioned above, we do a research on: “Interactive effect of salt and drought stresses on growth of sugarcane plants under glasshouse conditions ”
Objectives and requirements
Evaluating the effect of salt stress and drought stress on growth of sugarcane plants
- Evaluating the effect of salt stress and drought tolerant to growth characteristics in sugarcane plants
- Evaluating the effect of salt stress and drought tolerant to physiological characteristics in sugarcane plants
LITERATURE REVIEW
Origin, classification and distribution of sugarcane
Sugarcane, a grass plant from the genus Saccharum in the tribe Andropogoneae, comprises 36 species and is native to warm tropical regions of Asia Its discovery by early civilizations led to its rapid spread and the enhancement of sugar production through crossbreeding, resulting in the complex hybrids that constitute all current commercial sugarcane and further boosting its popularity.
Sugarcane was domesticated around 8000 BC in New Guinea and gradually spread eastward to India, where organized sugar production began in the middle of the 1st millennium BC Initially, sugar was extracted by chewing the cane, but by the 5th century, Indian chemists developed a method to crystallize sucrose, facilitating its transport and increasing its value as a trade item This innovation led to the spread of sugarcane throughout Asia and the Middle East, particularly after Arab nations conquered Egypt and introduced sugarcane to the Mediterranean By 715 AD, sugarcane reached Spain, but it gained popularity in Europe during the Crusades, as countries like Spain, Portugal, Italy, and Cyprus became familiar with sugar imported from the Middle East.
In the 16th and 17th centuries, the Azores attempted to build a stable economy around sugarcane, but the discovery of more favorable lands in the New World led to the rapid introduction of sugarcane cultivation in the Americas Landowners established extensive plantations, and due to the challenging nature of sugarcane farming and the soaring demand for sugar, the organized slave trade from Africa became highly profitable As a result, over 12 million Africans were displaced, significantly boosting sugar production and ultimately lowering prices, making sugar accessible to a wider population by the 19th century.
Sugarcane is currently the world's largest crop, with over 23.8 million hectares cultivated across more than 90 countries as of 2010, yielding a global harvest of 1.69 billion tonnes Brazil leads as the top producer, followed by India, China, Pakistan, Thailand, and Mexico Notably, sugarcane accounts for 75-80% of global sugar production, while sugar beet, which thrives in Europe, contributes to the remainder.
Sugarcane or sugar cane refer to several species and hybrids of tall perennial grass in the familyPoaceae,the classLiliopsida, the order
Poalesand the genus SaccharumL The scientific name of sugarcane is
Sugarcane is rich in antioxidants that boost immunity and combat infections Its high levels of calcium, magnesium, iron, and electrolytes make it effective for hydration and a remedy for the common cold and fevers by enhancing the body's protein levels Consuming raw sugarcane juice offers numerous health benefits and essential nutrients Additionally, sugarcane serves as a primary ingredient for products like molasses, jaggery, rum, ethanol, and biofuel It is also abundant in vitamins such as B1, B2, B6, and C, along with inorganic salts like iron and calcium, and organic acids including fumaric, succinic, citric, and malic acid.
Situation of Sugarcane production on the world and in Vietnam
2.2.1 Situation of Sugarcane production in the world
Sugarcane is the primary raw material for the sugar processing industry, contributing over 60% of global crude sugar production This nutrient-rich plant provides essential elements such as protein, calcium, and minerals, and is crucial for energy, hydration, and digestion Beyond sugar, sugarcane serves as a versatile resource for various industries, including alcohol, paper, pharmaceuticals, and biofuels, with by-products potentially yielding 3-4 times the value of sugar itself Sugarcane can be harvested multiple times from a single planting, with the first crop often yielding more than subsequent ones, thus enhancing economic value by reducing production costs Its large leaf area index and efficient sunlight utilization allow for significant yields, while its adaptability to diverse ecological conditions makes it resilient to environmental challenges The global sugar industry has seen substantial growth since the 16th century, with production rapidly increasing to meet rising consumption demands.
18 million tons / year, so far it has reached over 170 million tons / year.
According to FAOSTAT, by the end of the year 2018, sugarcane has been cultivated in 104 different countries including countries with large area: Brazil, India, China, Australia, Mexico, Indonesia and United
Brazil is the leading country in sugarcane cultivation, covering an area of 10 million hectares, significantly surpassing India and China, which have 4.7 million hectares and 1.4 million hectares, respectively Additionally, Brazil ranks first globally in sugarcane production, yielding approximately 746.8 million tons, which constitutes about 39.16% of the world's total production (FAOSTAT, 2018).
Table 2.1: World sugarcane production in recent years
Table 2.1 illustrates significant changes in the global sugarcane industry, highlighting a notable increase in harvested area from approximately 23.69 million hectares in 2010 to around 26.27 million hectares by 2018 Sugarcane yield experienced fluctuations, peaking at 78.31 tons per hectare in 2010, declining to 77.69 tons per hectare in 2016, and then surging to 80.02 tons per hectare in 2018 The highest production level was recorded in 2018, reaching 1,907.02 million tons, while 2014 marked the largest harvested area at 27.10 million hectares.
Table 2.2 Sugarcane production in major continents in recent years
Table 2.2 reveals a significant increase in sugarcane production across major continents from 2017 to 2018, with Asia leading the rise at approximately 56,000 million tons, followed by America and Africa, which also showed notable growth.
In 2018, the Americas led in sugarcane harvested area, covering 13.920 million hectares, despite a decline of 44 million hectares from 2017 Notably, the sugarcane yield increased from 80.711 to 80.994 tons per hectare, while total production rose from 1,022.448 to 1,022.786 million tons In contrast, Europe and Oceania experienced significant decreases in sugarcane production, with Europe losing nearly 400 million tons and Oceania over 3,000 tons.
From 2017 to 2018, Asia made significant strides in sugarcane cultivation, resulting in increased harvested area, yield, and production Notably, the sugarcane yield in Asia reached 80.628 tons per hectare in 2018, closely approaching the Americas' yield of 80.994 tons per hectare.
Oceania and Europe are the smallest continents in terms of harvested area for sugarcane, experiencing a significant decline in both yield and production While the harvested area saw a minor decrease of less than 0.01 million hectares, the yield dramatically fell from 5,000 to 15,000 tons per hectare.
2.2.2 Situation of Sugarcane production in Vietnam
The sugar cane industry in Vietnam has a long history, with the production of molasses and sugar dating back to ancient times However, significant development in the sugar industry began in the 1990s By 1994, Vietnam had only 9 sugar cane factories, with a combined capacity of less than 11,000 tons of sugarcane per day.
Vietnam's sugar industry faces challenges due to two small, outdated refineries, necessitating the import of 300,000 to 500,000 tons of sugar annually To address significant inefficiencies in domestic sugar production, a sugar program was initiated in 1995, marking a pivotal step towards industrialization and modernization This initiative aims to enhance rural agriculture, eradicate hunger, alleviate poverty, and create jobs for agricultural workers Sugar cane, a vital crop in Vietnam, is cultivated across various ecological regions, with a concentration in the North Central Coast (Nghe An, Thanh Hoa), Northern provinces (Hoa Binh, Son La), and the South Central Coast and Central Highlands.
In Vietnam, sugarcane cultivation has received limited attention, resulting in a relatively small growing area From 2004 to 2016, the sugarcane area experienced slight fluctuations, peaking at 0.3 million hectares in 2014 While productivity showed a significant increase from 2010 to 2014, it remains below the global average Although annual output has risen, it has not been consistent, with production reaching 17.3 million tons in 2007 and dropping to 15.6 million tons in 2009.
Table 2.4 Sugarcane acreage, productivity and production in Vietnam in the period 2004 - 2016
Source: Food and Agriculture Organization of the United Nations (FAO, 2016).
In recent years, climate change has significantly impacted sugarcane cultivation in our country, leading to challenges such as drought, flooding, and rising temperatures These factors have resulted in a notable decline in both sugarcane productivity and overall production Many regions are experiencing low yields, ineffective cultivation practices, or even crop loss Additionally, the area dedicated to sugarcane farming is shrinking due to external influences, including pests, diseases, and outdated farming techniques.
According to the General Statistics Office of Vietnam, sugarcane acreage and production are the largest in Thanh Hoa and Gia Lai provinces (Table
4) In general, the acreage and output of the provinces across the country tend to increase, the sugarcane acreage is increasingly being expanded to other provinces.
Table 2.5 Sugarcane acreage and yield in some provinces in the country in 2014 - 2015
Source: General Statistics Office of Vietnam 2016
Cultivation technique is one of the reasons affecting the productivity and quality of sugarcane The Department of Agriculture and Rural
The sugarcane production process has been established by Development, with specific procedures tailored to each variety and planting season in the raw material areas of companies However, farmers often fail to implement these processes correctly, leading to untimely pest control, which significantly impacts the productivity and quality of sugarcane Pests and diseases are critical factors that further diminish sugarcane yields, particularly in provinces like Nghe An and Thanh Hoa (Nguyen Dinh Huong, 2016).
Facing this situation, many localities have switched to other crops with higher economic value, but the effect is not stable, especially for Nghe
An province, where the largest sugarcane area in the country today.
To enhance sugarcane productivity and yield, it is essential to consider various factors, including land mechanization and cultivation methods A primary focus is on selecting and developing sugarcane varieties that improve productivity, output, and resilience to adverse conditions Consequently, sugar companies are implementing targeted policies each production season to boost production and increase overall productivity in the sugar industry.
2.2.3 Some research results on drought tolerance on some crops in the world and Vietnam
Drought is a prevalent natural occurrence that significantly impacts water availability for plants It leads to osmotic stress and various disturbances, affecting growth rates, water conditions, and the ion transport and absorption systems in plants.
Drought leads to water scarcity in plants, disrupting essential physiological and biochemical processes, which negatively impacts crop growth and productivity, particularly in sugarcane During drought conditions, cellular protoplasm undergoes changes that affect cell permeability, hydration levels, pH, viscosity, and protozoan structure, ultimately influencing plant metabolism The severity of drought results in varying effects on plant growth, physiology, and yield (Guyton, 2003) Drought is characterized by plant dehydration, which can stem from direct water shortages or secondary factors such as low temperatures, heat, or salinity.
MATERIAL AND METHOD
Object
- Sugarcane: 25 days old of sugarcane seedlings were used in this experiment Sugarcane seedlings were propagation from six-month old sugarcane plant of Cao Phong - Hoa Binh variety.
Figure 1: Sugarcane seedlings before transplanting to pots
Figure 2: NaCl salt use in experiment
Materials
- Tools: Pots, measure, scale, oven, EC meter, Spad meter, chlorophyll fluorescence meter.
Location and time
- The experiment was conducted under net-house condition Faculty of Agronomy, Vietnam National University of Agriculture, Trau Quy commune, Gia Lam district, Hanoi
Figure 3 Net- house of Advance program
Experimental design
Hom mía (23/0/2020) Plant star to sprout (28/9/2020)
Move the seedling to the pot (17/10/2020)
Before salinity Salinity - stress stage
After 14 days End cause salinity, the plant recovers
After 10 days Collect samples 1 st time
After 3 weeks Collect sample 2 nd time
After 8 daysCollect sample 3 rd time
Methods
- There are two factors in this study:
+ The first factors is drought stress in sugarcane plants
The experiment assessed the impact of drought stress on the growth, physiology, and yield of various sugarcane plant varieties Soil moisture levels were maintained at 75–80% water holding capacity (WHC) for the control group (D-C) and at 20–25% WHC to simulate high drought stress (D-H).
+ The second factors is the different of salinity ( NaCl concentration)
- The experiment evaluated the effect of salinity conditions on growth, physiology and yield of sugarcane plants varieties and causing salinity of
0 mM NaCl (control) and 100 mM NaCl.
- This experiment is grown in pots placed in a covered net house Plastic pots with holes used for planting trees (27 x 22 x 23 cm) will be filled up with 10kg of soil mixture.
At the conclusion of the seedling phase, salinity is managed by incorporating salt into the nutrient solution, ensuring uniform nutrient distribution across all pots Salt application is halted once the plants reach the ripening stage Key characteristics will be monitored and documented throughout this process.
+ Plant height (cm): Measure the stem from the base to the top.
+ Stalk diameter (cm): Measure at 10 cm from above ground.
+ Total leaves number: weekly from transplanting to finish Total visible leaves were counted
+ Leaf size (cm): Measure the length and width of the same leaf
+ The last number of leaf (leaves)
+ SPAD chlorophyll readings were measured by using portable chlorophyll meters (SPAD-502, Minolta, Japan).
Chlorophyll fluorescence (Fv/Fm) was measured using an Opti-Sciences Chlorophyll Fluorometer (Model OS-30p) at the second top visible leaf The fluorescence assessments were conducted between 10:00 AM and 12:00 PM, following a half-hour period of wrapping foil around a specific point on the leaf.
Water saturation deficit (WSD) was calculated using 1 cm leaf segments based on the method by Slavík (1963) The formula for WSD is given by WSD (%) = \(\left[\frac{(FM1 - FM0)}{(FM1 - DM)}\right] \times 100\), where FM1 represents the mass of fully water-saturated leaf segments, FM0 is the fresh mass of leaf segments under experimental conditions, and DM is the dry mass of the same segments Additionally, root fresh weight, stem fresh weight, leaf fresh weight, and leaf area were measured on the final day of the experiment.
Data recorded for growth, physiology and yield were analyzed using IRISTAT 5.0 Mean separations were calculated using Duncan’s multiple range tests at P0.05.
RESULT AND DISCUSSION
The effect of salinity stress and drought stress on growth and development of sugarcane
4.1.1 The effect of salinity stress and drought stress on plant height of sugarcane
Plant height is a crucial growth parameter that influences yield and is primarily determined by the genetic traits of the plant variety Factors such as planting density, cultivation methods, pest and disease presence, nutrient availability, and environmental conditions like humidity, temperature, and light density also play significant roles Consequently, tracking the growth dynamics of the main stem height is essential for evaluating the effects of drought and salinity on sugarcane growth.
Figure 4.1 Growth dynamics of plant height of sugarcane are influenced by salinity and drought conditions
Monitoring the effects of salinity and drought on plant height growth dynamics of Sugarcane, the results are presented in graph 4.1, we can see
In the initial phase of salinity stress, plant height generally increased, although the growth varied among treatments The T3 treatment (salinity) exhibited the lowest plant height compared to the other treatments After 7 days of salinity exposure, plant height continued to rise in most treatments, except for those affected by drought-induced salinity, which showed a decrease Specifically, the T2 treatment (Drought - Without salinity) recorded the maximum height of 121.36 cm, followed closely by the T1 treatment (Without salt - Without drought) at 120.21 cm In contrast, the T3 (Salinity - Without drought) and T4 (Salinity - Drought) treatments had the lowest heights at 115.50 cm and 117.83 cm, respectively.
During drought stress, plant height decreases significantly, with the control formula (T1) measuring 132.56 cm The T2 formula follows at 125.98 cm, while the lowest heights are observed in formulas T3 and T4, at 120.99 cm and 123.9 cm, respectively.
After 2 weeks of watering again and restoring plant height there is a more obvious change Control formula (T1) reached with maximum height is 137.08 (cm), followed by the T2 treatment has reached the value of 130.90 (cm) The formula with the lowest height is T3 and T4 treatments is 122.02 (cm) and 120.53 (cm), respectively The recovery capacity between the formulas compared with the control was different.After 2 weeks of watering again, the control formula had the highest recovery capacity, two treatments T3 and T4 had the lowest variation.Thus, the salinity and drought conditions affect the height of the main stem of the tree, the different salt and drought conditions, the variation in plant height will be different.
Figure 4.2: Plant height of each formula compared to the control formula
4.1.2.The effect of salinity stress and drought stress on the plant diameter of sugarcane
Figure 4.3: The growth of plant diameter are influenced by salinity and drought conditions
The growth characteristics of a tree, including the diameter of the plant and the height of the main stem, are influenced by both internal factors and external conditions Monitoring the dynamics of stem diameter is essential for assessing the effects of salinity and drought on sugarcane growth.
The effects of salinity and drought on plant diameter growth dynamics are illustrated in Figure 4.3 Under salinity stress, the diameters of the four formulas generally increased, with the T3 formula (Salinity - Without Drought) showing the least growth Post-salinity stress, the control formula and T2 formula (Drought - Without Salinity) exhibited growths of 15.22 mm and 15.19 mm, respectively The T4 formula (Salinity - Drought) followed with a diameter of 14.137 mm, while the T3 formula recorded the lowest diameter at 12.88 mm.
Drought stress significantly affected plant body diameter, with the control group (T1) exhibiting the largest diameter at 18.69 mm The T2 and T3 formulas followed, showing diameters of 16.21 mm and 15.44 mm, respectively In contrast, the Salinity - Drought formula (T4) recorded the smallest diameter at 14.63 mm.
During the Watering back stage, the control group (Formula T1) exhibited the highest increase in plant diameter at 21.35 mm In contrast, the other three formulas showed a decrease in diameter, with Formula T2 at 15.69 mm and Formula T3 at 14.92 mm The lowest stem diameter was observed in Formula T4, measuring 13.49 mm These findings indicate that salinity and drought conditions significantly affect the growth of sugarcane plants, particularly highlighting that Formula T4 has the least recovery ability in stem diameter, followed by Formula T3, and then Formula T2.
4.1.3 The effects of salinity stress and drought stress on the number of leaves of Sugarcane
Leaves are crucial for plants as they absorb sunlight, driving photosynthesis, which accounts for 90-95% of the dry matter accumulation The quantity of leaves significantly influences plant growth and productivity Research indicates that both salinity and drought conditions impact the rate of leaf production and the total leaf count.
During the period from the pre-salinity stage to seven days post-salinity, the number of leaves exhibited minimal change, showing a steady increase across four specific formulas The control formula recorded an average of 7.58 leaves per plant, while formulas T2 and T3 displayed similar results with 7.42 leaves per plant In contrast, formula T4 had the lowest count, averaging 7.25 leaves per plant.
Figure 4.4 The effects of salinity stress and drought stress on the number of leaves of Sugarcane
During the drought stress period, significant differences were observed in the number of leaves among the four treatments The control treatment T1 exhibited the highest increase, with an average of 9.25 leaves per plant, while treatment T3 showed the lowest increase at 7.92 leaves per plant Treatments T2 and T4 had intermediate results, with 8.25 and 8.08 leaves per plant, respectively.
The leaf counts of the four formulas show significant variation, with Formula T1 exhibiting the highest number at 9.63 leaves per plant Formula T4 follows with a minimum of 8.00 leaves per plant, while T2 and T3 have 8.75 and 8.38 leaves per plant, respectively Consequently, the impact of salinity and drought on leaf count was most pronounced in treatment T4, followed by treatments T3 and T2.
4.1.4 The effect of salinity stress and drought stress on leaf length growth of sugarcane
Salinity and drought stress significantly influenced both the number and length of leaves Under salinity stress, the control treatment T1 exhibited the longest leaf length at 93.65 cm, while treatments T2 and T3 recorded lengths of 86.2 cm and 86.12 cm, respectively.
Salinity - drought (T4) formula had the lowest leaf length of 84.23 (cm)
At 7 days after salinity stress Control treatment T1 still had the highest leaf length at 95.41 (cm), followed by two treatments T2 and T3 respectively 91.76 (cm) and 90.54 (cm) in length The lowest leaf length is the formula T4 with 87.04 (cm).
Figure 4.5 The effect of salinity stress and drought stress on leaf length growth of sugarcane
At the drought stress, the leaf length of the control formula was
106.3(cm) The formula T2 and T3 have the value of 102.31 (cm) and 95.05 (cm), respectively The lowest leaf length was the formula T4 reaching 95 (cm)
Following the drought stress, the recovery period involved re-watering the plants The control formula exhibited the longest leaf length at 110.275 cm, while the T2 formula measured 104.98 cm The T3 formula showed a leaf length of 94.71 cm, and the T4 treatment recorded the shortest leaf length at 93.15 cm.
The effect of salinity stress and drought stress on physiology of sugarcane
4.2.1 Effect of salinity stress and drought stress on SPAD index of sugarcane
Chlorophyll content serves as a crucial indicator for evaluating plant growth rates, as it directly influences photosynthesis There is a positive correlation between chlorophyll content and the leaf photosynthesis rate The SPAD value, which measures chlorophyll content, indicates that higher SPAD values correspond to increased chlorophyll levels, while lower SPAD values reflect reduced chlorophyll content Additionally, the SPAD index exhibits significant variations across different treatments.
Figure 4.7 Effect of salinity stress and drought stress on SPAD index of sugarcane
Before experiencing salinity stress, the SPAD index exhibited significant variation, with the control formula T1 showing the highest SPAD index at 48.78 In contrast, formula T4 recorded the lowest index at 43.35, while formulas T2 and T3 had SPAD indices of 45.87 and 44.05, respectively.
In the 10-day After salinity stress stage, treatment T1 exhibited the highest SPAD index at 46.51, while treatment T4 recorded the lowest index of 40.87 Treatments T2 and T3 showed SPAD indexes of 44.05 and 41.75, respectively.
Following the drought stress stage, the SPAD values exhibited a significant decline across the formulas The control formula T1 recorded the highest SPAD index at 41.03, while the lowest was observed in formula T4 at 28.57 Formulas T2 and T3 showed SPAD indices of 29.40 and 33.31, respectively.
During the re-watering stage, the plant shows signs of recovery, with the SPAD index for formula T1 reaching 40.89, while formulas T2 and T3 have indices of 23.46 and 28.53, respectively, and formula T4 has the lowest value at 22.97 This indicates that the impact of salinity and drought stress on the SPAD index varied across the four formulas during the three periods studied Notably, the SPAD indices for treatments T2, T3, and T4 were lower than that of treatment T1, suggesting that the recovery in these three treatments was less effective compared to treatment T1.
4.2.2 The effect of salinity and drought stress to chlorophyll fluorescence performance indices (Fv/Fm)
Chlorophyll fluorescence efficiency (Fv / Fm) serves as an indicator of the photosynthetic apparatus's physiological state during adverse conditions Research has demonstrated that salinity and drought stress negatively impact chlorophyll content, leading to damage in chlorophyll proteins and the photochemical system II (PS II), which are directly reflected in the variable parameters of chlorophyll fluorescence.
The study on the impact of dosage and conditions on the chlorophyll fluorescence index of white sugarcane revealed a gradual increase in the index over the follow-up periods Nonetheless, the analysis indicated no significant differences in the chlorophyll fluorescence efficiency index among the various formulas of the white sugarcane variety.
In the study of salinity stress, the control treatment T1 exhibited the highest chlorophyll fluorescence value at 0.77, while treatment T4 recorded the lowest at 0.70 Treatments T2 and T3 showed intermediate values of 0.71 and 0.72, respectively.
Figure 4.8 The effect of salinity and drought stress to chlorophyll fluorescence performance indices (Fv/Fm)
At the After salinity stage, the control formula exhibited the highest chlorophyll fluorescence value, while treatment T3 recorded the lowest values of 0.74 and 0.67, respectively, with treatments T2 and T3 showing similar results During the drought stress period, the T1 formula achieved the highest chlorophyll fluorescence value of 0.70, whereas the T4 formula had the lowest at 0.61 Treatments T2 and T3 had values of 0.65 and 0.69, respectively.
During the re-watering phase, as plants begin to recover, the chlorophyll fluorescence index shows an upward trend Among the tested formulas, T1 exhibits the highest index value at 0.85, while T2 records the lowest at 0.73 Formulas T3 and T4 follow with values of 0.77 and 0.75, respectively.
The study examines the impact of salinity and drought stress on the chlorophyll fluorescence index across four formulations over three distinct periods Notably, during the recovery stage, the chlorophyll fluorescence index of treatment T2 shows significant results.
T3, and T4 decreased significantly compared to T1 treatment, but there was a tendency to increase recovery.
4.2.3 The effect of salinity stress - drought stress to water saturation deficit (WSD)
Figure 4.9 The effect of salinity stress - drought stress to water saturation deficit (WSD)
Water saturation deficit (WSD) quantifies the water balance in plants, indicating their ability to retain moisture Drought-tolerant plants typically exhibit a higher tissue water content compared to less resilient varieties when faced with drought conditions.
Therefore, research on the shortage of storms and trenches is a necessary indicator The effect of salinity - drought stress on saturated water deficit is shown in figure 4.9.
After the drought stage, the T4 formula exhibited the highest saturation water deficit at 45.24, while the T1 formula showed the lowest at 22.54 The T2 and T3 formulas recorded saturation water deficit values of 32.44 and 31.65, respectively.
At the watering back stage, the saturated water deficit of the formulas tends to increase The highest increase is the formula T4 reaching a value of 49.00 Formula T1, T2, T3 are respectively 23.2, 35.26, 33.79.
The analysis reveals that from the post-drought period to the re-watering phase, the saturation levels of the four formulas show an upward trend, with formula T4 exhibiting the most significant increase, while formula T1 records the lowest values during both stages.
4.2.4 Evaluate of significant differences in the fresh and dry weight of roots between each treatment
Table 4.1 Evaluate of significant differences in the fresh and dry mass of roots between each treatment
Stage Treatment Fresh mass of roots
Degrad ation of fresh mass of roots compar ed to the control (%)
Degrad ation of dry mass of roots compar ed to the control (%)
Drought (T2) 10.295 a 11.06 2.39 10.15 Salinity (T3) 11.575 a 26.16 2.66 2.21 Salinity+Drou ght (T4) 13.685 b -32.93 2.905 -21.55 LSD 5% treatment 2.61562 0.553823
Treatment Fresh mass of roots Dry mass of roots
Treatment Fresh mass of roots Dry mass of roots
Drought (T2) 6.405 a 40.39 1.01 a 30.10 Salinity (T3) 10.745 c -16.86 1.445 a 12.42 Salinity+Drou ght 15.715 d -145.36 2.16 c -113.86
Roots play a crucial role in plants by absorbing water, nutrients, and minerals essential for growth The fresh biomass of a tree significantly influences crop yield, and a plant's ability to accumulate biomass is affected by various factors, including its variety and farming practices The capacity for dry matter accumulation indicates a plant's efficiency in transporting and storing matter, which is vital for assessing growth Therefore, investigating root mass is essential for understanding the impacts of saline conditions and drought on sugarcane growth, as detailed in Table 4.1.
At the after-salinity stage, at the fresh weight of the root indicator, formula T2 (10.295a) and formula T3 (11.575a) were the same group, not different It was different from control T1 (15,675b) and formula T4
The loss of fresh matter weight of T2 and T3 formula was 11.06% and 26.16%, respectively, smaller than the control formula, the treatment T4 had -32.93% decrease higher than control.