Method for improving drought resistance of endangered plant penchong tree

Abstract

The application provides a method for improving drought resistance of endangered plant pen container tree, which mainly studies drought resistance characteristics of pen container trees with different seedling ages, uses plant growth regulators and manages after drought stress to improve drought resistance of the endangered plant pen container tree and promote its field return. The technical scheme of the application mainly applies uniform foliar spraying of exogenous growth regulators, the exogenous growth regulators are a mixed solution of melatonin, Na2SiO3.9H2O2 and strigolactone, the spraying is continuously performed before drought stress, and meanwhile, drought stress and recovery irrigation management are combined, and Na2SiO3.9H2O2 and / or melatonin are continuously sprayed to achieve the purpose of improving drought resistance of the endangered plant pen container tree.

Description

Technical Field

[0001] This invention relates to the field of agricultural cultivation technology, specifically a method for improving the drought resistance of the endangered plant *Pencil Tree*. Background Technology

[0002] The tree fern (Sphaeropteris lepifera), belonging to the genus Sphaeropteris in the family Cyatheaceae, is listed as a Class II protected plant in China and is also included in the International Union for Conservation of Nature's (IUCN) list of endangered species. Conservation efforts include new cultivation methods to increase its population, as well as tissue culture and greenhouse seedling cultivation to improve its propagation survival rate.

[0003] The reasons for plant endangerment are complex. Inappropriate human activities, climate change, and the spread of invasive alien species are all major contributing factors to plant species becoming endangered. Years of research have revealed that water is a crucial environmental factor affecting the reintroduction and growth of the endangered *Pterocarya stenoptera* (pencil tree) in the wild. Under drought stress, *Pterocarya stenoptera* experiences physiological and biochemical metabolic imbalances through ion toxicity and osmotic stress, thus affecting its growth and development. During its propagation, *Pterocarya stenoptera* typically exhibits relatively weak drought resistance under natural conditions. Therefore, selecting appropriate watering frequencies and clarifying its drought resistance are important research areas in *Pterocarya stenoptera* cultivation techniques. Currently, the water requirements for *Pterocarya stenoptera* growth are not fully understood. Conducting drought stress experiments on *Pterocarya stenoptera*, studying the growth dynamics and changes in water content and other indicators of mature and juvenile *Pterocarya stenoptera* under different drought conditions, can provide a theoretical basis for understanding the plant's adaptability to drought stress. Therefore, improving the drought resistance of *Pterocarya stenoptera* is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the drought resistance of the endangered plant *Prunus pentaphyllum*, which can enhance its drought resistance and promote its return to the wild.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for improving the drought resistance of the endangered plant *Prunus pentaphyllum* includes: (1) selecting one-year-old potted *Prunus pentaphyllum* seedlings; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 50-80 μM / L, Na2SiO3·9H2O2 at a concentration of 3-5 mM / L, and strigolactone at a concentration of 20-40 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume proportions; spraying once in the morning and once in the evening for 5 consecutive days; (3) starting drought stress for 3 days on the second day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) on the fourth day, spraying Na2SiO3·9H2O2 at a concentration of 3-5 mM / L and melatonin at a concentration of 50-80 μM / L, spraying once in the evening for 3 consecutive days; and starting normal watering on the fourth day.

[0007] A method for improving the drought resistance of the endangered plant *Prunus pentaphyllum* includes: (1) selecting four-year-old mature potted *Prunus pentaphyllum* seedlings; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 50-80 μM / L, Na2SiO3·9H2O2 at a concentration of 3-5 mM / L, and strigolactone at a concentration of 20-40 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume proportions; spraying once in the morning and once in the evening for 3 days; (3) starting drought stress for 5 days on the second day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) spraying melatonin at a concentration of 50-80 μM / L on the 6th day, spraying once in the evening, and spraying continuously for 3 days; and starting normal watering on the 6th day.

[0008] Furthermore, "resumption of watering" refers to resuming watering in the evening after a day of drought stress, and this watering should be thorough. "Normal watering" means maintaining the normal amount of water each time, keeping the soil moisture content at 70-80%.

[0009] Furthermore, the substrate is composed of peat, perlite, and rice husks in a volume ratio of 0.46:0.27:0.27; the pH value of the substrate is 5-5.5; the fertilizer content in the substrate is 225-240 g / kg of organic matter, 0.15-0.20 g / kg of available phosphorus, 0.20-0.30 g / kg of available potassium, 0.20-0.40 g / kg of available nitrogen, and the bulk density is 0.45-0.55 g / cm³. 3 The maximum water holding capacity is 300-320%.

[0010] Furthermore, the specifications for a one-year-old pen holder tree bonsai are as follows: base diameter: 10±0.2cm; height: 14±0.2cm; mouth diameter: 14±0.2cm; and specifications for a four-year-old pen holder tree bonsai are as follows: base diameter: 42±0.2cm; height: 38±0.2cm; mouth diameter: 45±0.2cm.

[0011] Furthermore, the temperature is 22-26℃, and the air humidity is 70%-80%.

[0012] Furthermore, normal watering means maintaining the normal amount of water each time, keeping the soil moisture content at 75%.

[0013] Furthermore, the temperature is 25℃, and the air humidity is 80% for one-year-old *Pencil Cactus* and 70% for four-year-old *Pencil Cactus*.

[0014] Furthermore, for one-year-old penholder trees, the exogenous growth regulator in step (2) is a mixed solution of 50 μM / L melatonin, 3 mM / L Na2SiO3·9H2O2 and 20 μM / L strigolactone; the exogenous growth regulator in step (4) is a mixed solution of 5 mM / L Na2SiO3·9H2O2 and 80 μM / L melatonin.

[0015] Furthermore, for four-year-old penholder trees, the exogenous growth regulator in step (2) is a mixed solution of 80 μM / L melatonin, 5 mM / L Na2SiO3·9H2O2 and 40 μM / L strigolactone, and the exogenous growth regulator in step (4) is 80 μM / L melatonin.

[0016] The beneficial effects of this application are:

[0017] 1. Exogenous silicon is also a plant growth regulator. After contact with plants, it can quickly penetrate into the plant body and improve cell vitality. It can accelerate the growth rate of plant roots and promote plant growth and development. This invention is the first to discover that exogenous silicon, along with melatonin and strigolactone, can work together to improve the drought resistance of *Prunus armeniaca*.

[0018] 2. Through morphological observation and leaf moisture content measurement, we found that the drought resistance of one-year-old seedlings was relatively poor. After more than 3 days of drought stress, the leaves could hardly recover growth and the leaf moisture content continued to decline. In contrast, the drought resistance of four-year-old mature pen holder trees was stronger than that of one-year-old seedlings. After the application of the growth regulator in the example, even if watering resumed after 5 days of drought stress, although there was a brief decline, the leaf moisture content could be restored to normal and maintained in a healthy and stable state.

[0019] 3. We further verified the above conclusions by analyzing the physicochemical properties of *Pterocarya stenoptera* leaves under drought stress. Specifically, for one-year-old *Pterocarya stenoptera* seedlings, spraying with a mixed solution of exogenous growth regulators (50 μM / L melatonin, 3 mM / L Na₂SiO₃·9H₂O₂, and 20 μM / L strigolactone) for 5 consecutive days before stress, followed by spraying with 5 mM / L Na₂SiO₃·9H₂O₂ and 80 μM / L melatonin for 3 days after 3 days of drought stress, significantly improved the drought resistance of one-year-old seedlings. For four-year-old mature potted *Pterocarya stenoptera* seedlings, spraying with exogenous growth regulators (80 μM / L melatonin and 5 mM / L strigolactone) for 3 consecutive days before stress significantly improved the drought resistance of one-year-old seedlings. A mixed solution of Na2SiO3·9H2O2 and 40 μM / L strigolactone, followed by foliar spraying with 80 μM / L melatonin for 3 days after 5 days of drought stress, significantly improved the drought resistance of four-year-old mature *Pterocarya stenoptera*. By comparing the use of a single plant regulator with that used alone in the experimental examples, we found that the combined application of the plant regulators of this invention has a superior drought resistance effect in the early stages of drought stress in *Pterocarya stenoptera*.

[0020] 4. In addition to applying a combination of exogenous plant growth regulators and drought stress treatment, we also studied the effects of substrate ratio and growth environment on improving the drought resistance of *Pterocarya stenoptera*. We found that a suitable substrate ratio can maintain reasonable soil porosity and bulk density. Specifically, when the ratio of peat, perlite, and rice husk is 0.46:0.27:0.27, *Pterocarya stenoptera* can maintain normal root growth and improve photosynthetic capacity under drought stress conditions. Its leaves also show better transpiration rate and chlorophyll content. This treatment can alleviate the effects of drought stress on *Pterocarya stenoptera*. Furthermore, the optimal growth environment is a temperature of 25℃ and an air humidity of 80% for one-year-olds and 70% for four-year-olds. This promotes normal growth of *Pterocarya stenoptera* seedlings under drought stress conditions. These conditions, combined with the method of this invention, can alleviate the effects of drought stress on *Pterocarya stenoptera*. Attached Figure Description

[0021] Figure 1 The morphological changes of a one-year-old pen holder tree after three days of drought;

[0022] Figure 2 Morphological changes of a one-year-old pen holder tree after five days of drought;

[0023] Figure 3 Morphological changes of a one-year-old pen holder tree after seven days of drought;

[0024] Figure 4 The morphological changes of a four-year-old pen holder tree after three days of drought;

[0025] Figure 5 Morphological changes of a four-year-old pen holder tree after five days of drought;

[0026] Figure 6Morphological changes of a four-year-old pen holder tree after seven days of drought;

[0027] Figure 7 Graph showing the change in leaf moisture content of Penholderia cochinchinensis seedlings under different drought treatments over one year;

[0028] Figure 8 Graph showing the changes in leaf moisture content of four-year-old Penholderia saplings under different drought treatments;

[0029] Figure 9 Physicochemical analysis of leaves from one-year-old Penholderia spp. after treatment with different plant growth regulators;

[0030] Figure 10 Physicochemical analysis of leaves from four-year-old Penholderia arborescens seedlings treated with different plant growth regulators. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for improving the drought resistance of the endangered plant *Pterocarya stenoptera* includes: (1) selecting one-year-old potted seedlings of *Pterocarya stenoptera*; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 50 μM / L, Na2SiO3·9H2O2 at a concentration of 3 mM / L, and strigolactone at a concentration of 20 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume ratios; spraying once in the morning and once in the evening for 5 consecutive days; (3) starting drought stress for 3 days on the second day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) on the fourth day, spraying Na2SiO3·9H2O2 at a concentration of 5 mM / L and melatonin at a concentration of 80 μM / L, spraying once in the evening for 3 consecutive days; and starting normal watering on the fourth day. Resumption of watering refers to resuming watering in the evening after a day of drought stress, ensuring thorough watering. Normal watering means maintaining the normal amount of water each time, keeping the soil moisture content at 75%. Specifications for a one-year-old bonsai pen holder tree: base diameter: 10±0.2cm; height: 14±0.2cm; mouth diameter: 14±0.2cm; substrate composed of peat, perlite, and rice husks in a volume ratio of 0.46:0.27:0.27; indoor temperature 25℃, air humidity 80%.

[0034] Example 2

[0035] A method for improving the drought resistance of the endangered plant *Prunus pentaphyllum* includes: (1) selecting four-year-old mature potted *Prunus pentaphyllum* seedlings; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 80 μM / L, Na2SiO3·9H2O2 at a concentration of 5 mM / L, and strigolactone at a concentration of 40 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume proportions; spraying once in the morning and once in the evening for 3 days; (3) starting drought stress for 5 days the day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) spraying melatonin at a concentration of 80 μM / L on the 6th day, spraying once in the evening, and spraying continuously for 3 days; starting normal watering on the 6th day. Resuming watering means resuming watering in the evening after drought stress during the day, and resuming watering means watering thoroughly; normal watering means maintaining the normal amount of water each time, maintaining the soil moisture content at 75%. Specifications of a four-year-old bonsai tree (Pencil Holder Tree): Base diameter: 42±0.2cm; Height: 38±0.2cm; Mouth diameter: 45±0.2cm. The substrate consists of peat, perlite, and rice husks in a volume ratio of 0.46:0.27:0.27. The indoor temperature is 25℃, and the air humidity is 70%.

[0036] Example 3

[0037] A method for improving the drought resistance of the endangered plant *Pterocarya stenoptera* includes: (1) selecting one-year-old potted seedlings of *Pterocarya stenoptera*; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 50 μM / L, Na2SiO3·9H2O2 at a concentration of 3 mM / L, and strigolactone at a concentration of 20 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume ratios; spraying once in the morning and once in the evening for 5 consecutive days; (3) starting drought stress for 3 days on the second day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) on the fourth day, spraying Na2SiO3·9H2O2 at a concentration of 5 mM / L and melatonin at a concentration of 80 μM / L, spraying once in the evening for 3 consecutive days; and starting normal watering on the fourth day. Resumption of watering refers to resuming watering in the evening after a day of drought stress, ensuring thorough watering. Normal watering means maintaining the normal amount of water each time, keeping the soil moisture content at 75%. Specifications for a one-year-old bonsai pen holder tree: base diameter: 10±0.2cm; height: 14±0.2cm; mouth diameter: 14±0.2cm; substrate composed of peat, perlite, and rice husks in a volume ratio of 0.46:0.27:0.27; substrate pH: 5; organic matter content: 225-240g / kg; available phosphorus content: 0.15-0.20g / kg; available potassium content: 0.20-0.30g / kg; available nitrogen content: 0.20-0.40g / kg; bulk density: 0.45-0.55g / cm³. 3The maximum water holding capacity is 300-320%. The indoor temperature in all the above steps is 25℃, and the air humidity is 80%.

[0038] Example 4

[0039] A method for improving the drought resistance of the endangered plant *Prunus pentaphyllum* includes: (1) selecting four-year-old mature potted *Prunus pentaphyllum* seedlings; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 80 μM / L, Na2SiO3·9H2O2 at a concentration of 5 mM / L, and strigolactone at a concentration of 40 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume proportions; spraying once in the morning and once in the evening for 3 days; (3) starting drought stress for 5 days the day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) spraying melatonin at a concentration of 80 μM / L on the 6th day, spraying once in the evening, and spraying continuously for 3 days; starting normal watering on the 6th day. Resuming watering means resuming watering in the evening after drought stress during the day, and resuming watering means watering thoroughly; normal watering means maintaining the normal amount of water each time, maintaining the soil moisture content at 75%. Specifications of a four-year-old bonsai tree (Pencil Holder Tree): Base diameter: 42±0.2cm; Height: 38±0.2cm; Mouth diameter: 45±0.2cm. The substrate consists of peat, perlite, and rice husks in a volume ratio of 0.46:0.27:0.27. The substrate has a pH of 5, an organic matter content of 225-240g / kg, available phosphorus content of 0.15-0.20g / kg, available potassium content of 0.20-0.30g / kg, available nitrogen content of 0.20-0.40g / kg, and a bulk density of 0.45-0.55g / cm³. 3 The maximum water holding capacity is 300-320%. The indoor temperature in all the above steps is 25℃, and the air humidity is 70%.

[0040] Experiment 1: Study on drought resistance of *Prunus armeniaca* seedlings of different ages

[0041] Experimental Methods: In 2023, healthy one-year-old and four-year-old *Pterocarya stenoptera* seedlings with relatively uniform growth were selected in the greenhouse of the Zhejiang Subtropical Crops Research Institute. The drought stress method for one-year-old seedlings was the same as in Example 1, and for four-year-old seedlings, it was the same as in Example 2. Both one-year-old and four-year-old seedlings were divided into three groups, subjected to drought for 3, 5, and 7 days (see Table 1 for drought conditions). Watering was resumed after the required number of drought days, with watering once daily in the evening. Changes in morphological characteristics (see Table 2 for morphological photography schedule) and water content were observed. Three treatments were used, with two plants per treatment, in a randomized block design with three replicates. The method for determining the relative water content of leaves is as follows:

[0042] Wipe the surface moisture of the leaves dry, accurately weigh the fresh weight of the leaves as W1, place them in an envelope, and put the leaves in an oven. Set the temperature to 105℃ for 30 minutes to fix the green color, then adjust the temperature to 80℃ and dry until constant weight. Weigh the leaves at this point as W2. The calculation formula is as follows:

[0043] W = (W1 - W2) / W1, where: W—relative water content of leaves; W1—fresh weight of leaves; W2—dry weight of leaves.

[0044] Table 1. Watering conditions for different treatments of the penholder tree.

[0045]

[0046] Table 2. Photo numbers of each treatment of the penholder tree.

[0047]

[0048] A: A photo of the same potted pen holder tree under the same drought conditions on day 1.

[0049] B: Photos of the same potted pen holder tree under the same drought conditions, showing the number of days of drought reached, at which point the normal watering period will begin. The 3-day drought group shows the photo taken on day 3, and so on.

[0050] C: The same potted pen holder tree under the same drought conditions, photos taken 2 days after the designed number of drought days were reached and normal watering was resumed, photos taken on the 5th day for the 3-day drought group, and so on.

[0051] / : indicates that no photos were taken on this day.

[0052] Experimental results:

[0053] (1) Figure 1-6 To understand the morphological changes of *Pterocarya stenoptera* under different drought conditions, it was found that four-year-old and one-year-old *Pterocarya stenoptera* seedlings exhibited different resistance to stress, and therefore, the degree of drought stress they could tolerate also differed. It was observed that when three, five, and seven days of drought stress treatment were applied to both four-year-old and one-year-old *Pterocarya stenoptera* seedlings, the condition of the one-year-old seedlings under the same drought stress treatment was significantly worse than that of the four-year-old seedlings. Therefore, compared to four-year-old seedlings, we need to consider more the water requirements and drought resistance methods for one-year-old seedlings and four-year-old mature *Pterocarya stenoptera* seedlings at different ages. Meanwhile, according to the drought stress treatment gradient of 3, 5, and 7 days, the one-year-old seedlings showed the greatest stress damage on days 5 and 7. However, under the treatment in Example 1 of this application, the one-year-old seedlings showed better overall drought resistance on day 3 of drought stress. The 7-day drought stress morphology of the four-year-old pen holder tree was relatively poor, but in terms of leaf morphology, it showed stronger drought resistance than the one-year-old seedlings, with only a few leaves drying out but not wilting.

[0054] (2) Figure 7-8 The graph shows the changes in leaf moisture content of one-year-old and four-year-old *Pterocarya stenoptera* trees under different drought treatments. Measuring leaf moisture content allows for a more accurate assessment of the specific drought treatment and the changing patterns of leaf moisture status. It also further demonstrates that after the drought treatment ends and normal watering resumes, under the treatment method described in this application, one-year-old *Pterocarya stenoptera* seedlings can recover their growth after 3 days of drought stress, and four-year-old mature *Pterocarya stenoptera* trees after 5 days of drought stress. The four-year-old *Pterocarya stenoptera* trees treated with 3 days and 5 days of drought stress showed varying degrees of moisture content recovery after watering resumed. One-year-old seedlings have lower drought tolerance; after more than 3 days of drought stress, their leaves are unlikely to recover, and leaf moisture content continues to decline. Four-year-old mature *Pterocarya stenoptera* trees have stronger drought tolerance than one-year-old seedlings. With the application of the growth regulator in the example, even after 5 days of drought stress followed by watering, although there is a brief decrease, the leaf moisture content can recover to a normal state, maintaining an overall healthy homeostasis.

[0055] Experiment 2: Effects of different plant growth regulators on drought resistance of *Prunus armeniaca*

[0056] Experimental Methods: This application investigates the effects of different plant growth regulators or combinations thereof on the drought resistance of *Pterocarya stenoptera*, aiming to identify the most suitable regulators or combinations to enhance drought resistance. One-year-old *Pterocarya stenoptera* were treated with drought using the method described in Example 1, while four-year-old plants were treated with drought using the method described in Example 2. The plant growth regulators were replaced as shown in Table 3 below (A represents normal growth; B and K represent drought stress, with the specific methods the same as in Examples 1 or 2). Five plants were used in each treatment group, while the control group received normal water management. The experimental period was 28 days. Physiological indicators were sampled at 7:00 AM. Complete, healthy leaves from each plant were mixed and brought back to the laboratory for physiological indicator measurement, exploring the effects of different exogenous regulators on the physiological indicators of *Pterocarya stenoptera* after drought stress. Five plants were sampled in each group, with three replicates for each sample.

[0057] Table 3. Experimental groups with different exogenous plant growth regulators

[0058]

[0059] Experimental results:

[0060] Figure 9-10As shown, exogenous application of melatonin, strigolactone, and silicon treatment can alleviate the damage of *Pterocarya stenoptera* to drought stress to some extent. For one-year-old *Pterocarya stenoptera* seedlings, spraying with an exogenous growth regulator for 5 consecutive days before stress, namely a mixed solution of 50 μM / L melatonin, 3 mM / L Na2SiO3·9H2O2, and 20 μM / L strigolactone, followed by spraying with 5 mM / L Na2SiO3·9H2O2 and 80 μM / L melatonin for 3 days after 3 days of drought stress, can significantly improve the drought resistance of one-year-old *Pterocarya stenoptera* seedlings. For four-year-old mature potted *Pterocarya stenoptera* seedlings, applying an exogenous growth regulator for 3 consecutive days before stress, namely a mixed solution of 80 μM / L melatonin and 5 mM / L... A mixed solution of Na2SiO3·9H2O2 and 40 μM / L strigolactone, followed by foliar spraying with 80 μM / L melatonin for 3 days after 5 days of drought stress, significantly improved the drought resistance of four-year-old mature *Pterocarya stenoptera*. By comparing the use of a single plant regulator with that used alone in the experimental examples, we found that the combined application of the plant regulators of this invention has a superior drought resistance effect in the early stages of drought stress in *Pterocarya stenoptera*.

[0061] Data results show that under drought stress, the combined application of plant growth regulators significantly increased the total antioxidant capacity (T-AOC) activity, growth regrowth (GR) activity, and the content of soluble sugars and soluble proteins in one-year-old *Pterocarya stenoptera* seedlings. This indicates that the treatment with plant growth regulators can further enhance the activity of antioxidant enzymes in *Pterocarya stenoptera* when alleviating drought stress and maintain normal photosynthesis in its leaf cells. Simultaneously, it reduced the H2O2 and MDA content in the leaves, indicating that the application of plant growth regulators can reduce the impact of drought stress on *Pterocarya stenoptera*. After treatment, the intracellular H2O2 content of *Pterocarya stenoptera* seedlings was significantly reduced, alleviating membrane peroxidation damage and reducing MDA accumulation, thus mitigating and reducing the damage of salt stress to *Pterocarya stenoptera* seedlings.

[0062] Experiment 3: The effects of different growing environments on the drought resistance of *Prunus pendantica*

[0063] Experimental Methods: In addition to exploring the effects of plant growth regulator combinations and stress management methods on the drought resistance of *Pterocarya stenoptera* seedlings of different ages, we further investigated the influence of growth environment conditions on the drought resistance of *Pterocarya stenoptera*. One-year-old *Pterocarya stenoptera* were treated with drought using the method described in Example 3, while four-year-old *Pterocarya stenoptera* were treated with drought using the method described in Example 4. The growth environment conditions were replaced as shown in Table 4 below (CK1-2 represent normal growth; CK3-4 represent drought stress, where distilled water was used instead of the growth regulator, with the specific method being the same as in Examples 3 or 4). Five pots were used in each treatment group, while the control group received normal water management. The experimental period was 15 days. Physiological indicators were sampled at 7:00 AM. Intact and healthy leaves from the plants were selected and mixed for sampling, which was then brought back to the laboratory for physiological indicator measurement to explore the effects of different growth environments on the physiological indicators of *Pterocarya stenoptera* after drought stress. Five plants were sampled in each group, with three replicates for each sample.

[0064] Table 4. Effects of different growing environments on drought resistance of *Pencil Tree*.

[0065]

[0066] Experimental results:

[0067] In addition to applying a combination of exogenous plant growth regulators and drought stress treatment, we also studied the effects of substrate ratio and growth environment on improving the drought resistance of *Pterocarya stenoptera*. We found that a suitable substrate ratio can maintain reasonable soil porosity and bulk density. Specifically, when the ratio of peat, perlite, and rice husk is 0.46:0.27:0.27, *Pterocarya stenoptera* can maintain normal root growth and improve photosynthetic capacity under drought stress conditions. Its leaves also showed better transpiration rate and chlorophyll content. This treatment can alleviate the effects of drought stress on *Pterocarya stenoptera*. Furthermore, the optimal growth environment is an indoor temperature of 25℃ and an air humidity of 80% for one-year-olds and 70% for four-year-olds. This promotes normal growth of *Pterocarya stenoptera* seedlings under drought stress conditions. These conditions, combined with the methods in Examples 3-4 of this invention, can alleviate the effects of drought stress on *Pterocarya stenoptera*.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the drought resistance of the endangered plant *Prunus pendantica*, characterized in that, Specifically, this includes (1) selecting one-year-old seedlings of *Pendula sylvestris* for pot cultivation; (2) uniformly spraying the leaves with an exogenous growth regulator, wherein the exogenous growth regulator is a mixed solution of melatonin at a concentration of 50-80 μM / L, Na2SiO3·9H2O2 at a concentration of 3-5 mM / L, and strigolactone at a concentration of 20-40 μM / L, wherein the mixed solution is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume proportions; spraying once in the morning and once in the evening for 5 consecutive days; (3) starting drought stress for 3 days on the second day after spraying the exogenous growth regulator, and resuming watering in the evening; (4) spraying the exogenous growth regulator on the 4th day, wherein the exogenous growth regulator is at a concentration of 3-5 mM / L. A mixed solution of Na2SiO3·9H2O2 and melatonin at a concentration of 50-80 μM / L was sprayed once in the evening for three consecutive days; normal watering began on the fourth day; resume watering refers to watering in the evening after daytime drought stress, and resume watering means watering thoroughly; normal watering means maintaining the normal amount of water each time, keeping the soil moisture content at 70-80%; the substrate for the potted seedlings in step (1) consists of peat, perlite and rice husks, with a volume ratio of 0.46:0.27:0.27; the pH value of the substrate is 5-5.5, and the amount of fertilizer applied to the substrate is 225-240 g / kg of organic matter, 0.15-0.20 g / kg of available phosphorus, 0.20-0.30 g / kg of available potassium, 0.20-0.40 g / kg of available nitrogen, and 0.45-0.55 g / cm³ of bulk density. 3 The maximum water holding capacity is 300-320%.

2. A method for improving the drought resistance of the endangered plant *Pendula oblongifolia*, characterized in that, Specifically, this includes (1) selecting four-year-old mature potted pen holder tree seedlings; (2) uniformly spraying exogenous growth regulators on the foliage, wherein the exogenous growth regulators are melatonin with a concentration of 50-80 μM / L, Na2SiO3·9H2O2 with a concentration of 3-5 mM / L, and Na2SiO3·9H2O2 with a concentration of 20-40 μM / L. The mixed solution of strigolactone is prepared by first preparing the solutions of the above concentrations separately and then mixing them in equal volume ratios; spray once in the morning and once in the evening for 3 days; (3) after spraying the exogenous growth regulator, start drought stress for 5 days on the second day and resume watering in the evening; (4) spray the exogenous growth regulator on the 6th day, the exogenous growth regulator is melatonin with a concentration of 50-80μM / L, spray once in the evening and spray continuously for 3 days; start normal watering on the 6th day; resume watering means that after drought stress during the day, resume watering in the evening, and resume watering means watering thoroughly; normal watering means that each time the normal watering amount is maintained, and the soil moisture content is maintained at 70-80%; the substrate of the potted seedling in step (1) is composed of peat, perlite and rice husk, with a volume ratio of 0.46:0.27:0.27; the pH value of the substrate is 5-5.5, and the amount of fertilizer in the substrate is 225-240% organic matter content. g / kg, available phosphorus content is 0.15-0.20 g / kg, available potassium content is 0.20-0.30 g / kg, available nitrogen content is 0.20-0.40 g / kg, and bulk density is 0.45-0.55 g / cm³. 3 The maximum water holding capacity is 300-320%.

3. The method as described in claim 1, characterized in that, in, The bottom diameter of a one-year-old bonsai pen holder tree is 10±0.2cm. Height: 14±0.2cm; Diameter: 14±0.2cm; Indoor temperature: 25℃; Air humidity: 80% for one-year-old pen holder trees.

4. The method as described in claim 2, characterized in that, in, Specifications of a four-year-old bonsai pen holder tree: base diameter: 42±0.2cm; Height: 38±0.2cm; Diameter: 45±0.2cm; Indoor temperature: 25℃; Air humidity: 70% for a four-year-old pen holder tree.

5. The method as claimed in claim 1 or 2, characterized in that, in, Normal watering means maintaining the normal amount of water each time, keeping the soil moisture content at 75%.

6. The method of claim 1, characterized in that, The exogenous growth regulator in step (2) is a mixed solution of 50 μM / L melatonin, 3 mM / L Na2SiO3·9H2O2 and 20 μM / L strigolactone; the exogenous growth regulator in step (4) is a mixed solution of 5 mM / L Na2SiO3·9H2O2 and 80 μM / L melatonin.

7. The method of claim 2, characterized in that, The exogenous growth regulator in step (2) is a mixed solution of 80 μM / L melatonin, 5 mM / L Na2SiO3·9H2O2 and 40 μM / L strigolactone, and the exogenous growth regulator in step (4) is 80 μM / L melatonin.

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