**2. Materials and method**

**1. Introduction**

possible to further increase existing cultivating areas.

8 Physical Methods for Stimulation of Plant and Mushroom Development

cover into agricultural land requires great investment.

in the most populous parts of the world will double by 2025 [1].

Plants comprise the source of life on earth. In total, 90% of the energy and 80% of the protein consumed by humans are of plant origin. The remaining energy and protein requirements are met by animal products. Thousands of people die every year in many parts of the world due to hunger and malnutrition. It is necessary to increase crop production so that human beings can feed on a sufficient and balanced diet to sustain their existence on Earth. This can only be achieved by increasing the amount of yield obtained from each unit area of land, since it is not

It is estimated that world population will increase by 1.5% per year to 8 billion in 2020 and 11 billion in 2050 [1]. The area of land covering the Earth is 14 billion hectares. Currently, 10% of this land area is cultivated. About 20% of the world's land is covered with pastures, 20% with mountains, 20% with glaciers, and 20% with deserts. The remaining 10% of the area has a very shallow soil cover. Given the impossibility of agricultural activities in mountains and glacier-covered areas, there are areas of potential agriculture, such as marshlands, deserts, or areas with insufficient land cover. It is largely impossible to use pastures that cover rugged and very sloping areas as cultivating fields. The conversion of deserts and inadequate land

In parallel with increasing population, agricultural areas are being used for other nonagricultural purposes (settlement, road, factory, etc.) or are shrinking rapidly due to erosion, salinization, acidification, intensive agriculture, and overgrazing. It is estimated that agricultural land per capita, which is now 0.26 hectares, will decrease to 0.15 hectares by 2050. In addition, the availability of water resources for modern agriculture will become difficult due to increased water consumption and increasing water pollution [1]. It is expected that food requirements

The yield in agricultural production declines due to biotic and abiotic stress factors. Developing a resistant or tolerant cultivar against these stress factors is the main goal of plant breeding. Chemical methods are commonly used to combat biotic stressors (diseases and pests) that reduce crop production. However, the use of chemicals in agriculture causes an extra financial burden and pollutes the environment. In Turkey, 2.3 million tons of chemical fertilizer and 25,000 tons of pesticides (insecticides, fungicides, and herbicides) were used according to the data from 2013. In the last 25 years, it has emerged that the unconscious use of fertilizers and chemicals applied in plant production has negatively affected long-term ecological balance. For example, it has been determined that overused nitrogen fertilizers are washed from the soil and pollute drinking water and the seas, while the nitrogen components that are escaping from the gaseous state are adversely affecting the ozone layer, which protects the earth from harmful rays of the sun. In addition, herbicides and insecticides applied to combat weeds and pests have been shown to destroy the natural equilibrium in agricultural areas, causing the emergences of new diseases and pesticides. It has also been understood that certain chemicals, which have permanent effects, accumulate in plants, and this negatively affects the health of people and animals fed on those plants. As a result, it is

The study conducted by Taher et al. [5] was carried out in the research fields of the Faculty of Agriculture, Ankara University in the years of 2013 and 2014. Oil-type sunflower cultivars

• Third treatment: A total of four leaves were removed from the plant. Two of these leaves were taken from the below of the head, and the other two were taken from the middle of the plant. • Fourth treatment: A total of six leaves were removed from the plant. Three of these leaves were selected from the below of the head, and the remaining three from the middle of the plant. Plants were irrigated during development according to water need of the plants. During the application of irrigation, the most attention was given to watering each parcel equally. After the flowering and fertilization has been completed, the heads of the plants from which the measurements were taken were covered with paper bags to protect the seeds from damage by

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birds (**Figure 3**). Plants were harvested when 80% of sunflower heads were brown.

**Figure 2.** The places from where leaves were removed in "star-shaped head stage" (from below the head and from the

middle of the plant).

**Figure 1.** Sowing plan for sunflower cultivars according to the "randomized complete block, split-plots" design with three replications.

"08-TR-003," "TR-3080," and "TARSAN-1018" obtained from "Trakya Agricultural Research Institute" were used in the study. Soil of trial field was plowed 30 cm in depth in fall before winter. In spring, it was plowed again for 10–15 cm in depth to make soil ready for sowing. Sowing was performed in the first week of April with spaces of 70 cm inter-row and 25 cm on-row. Three seeds were put in each dibbling to guarantee the emergence. Two weeks after emergence, two of the plants were eliminated and only one plant left in each dibbling. For all defoliation treatments, plots were fertilized with 14 kg/da diammonium phosphate (DAP) before sowing. During growing, weed control was achieved by hand in experimental field. The study sowing plan is given in **Figure 1**.

When plants reached to "star-shaped head stage," which is the beginning of reproductive period, defoliation was carried out and the plants were labeled. Half of the leaves were removed from just below the head, while the other half was removed from the middle part of the plant for each defoliation treatment (**Figure 2**). Four different defoliation treatments were performed. They were:


Plants were irrigated during development according to water need of the plants. During the application of irrigation, the most attention was given to watering each parcel equally. After the flowering and fertilization has been completed, the heads of the plants from which the measurements were taken were covered with paper bags to protect the seeds from damage by birds (**Figure 3**). Plants were harvested when 80% of sunflower heads were brown.

"08-TR-003," "TR-3080," and "TARSAN-1018" obtained from "Trakya Agricultural Research Institute" were used in the study. Soil of trial field was plowed 30 cm in depth in fall before winter. In spring, it was plowed again for 10–15 cm in depth to make soil ready for sowing. Sowing was performed in the first week of April with spaces of 70 cm inter-row and 25 cm on-row. Three seeds were put in each dibbling to guarantee the emergence. Two weeks after emergence, two of the plants were eliminated and only one plant left in each dibbling. For all defoliation treatments, plots were fertilized with 14 kg/da diammonium phosphate (DAP) before sowing. During growing, weed control was achieved by hand in experimental field.

**Figure 1.** Sowing plan for sunflower cultivars according to the "randomized complete block, split-plots" design with

When plants reached to "star-shaped head stage," which is the beginning of reproductive period, defoliation was carried out and the plants were labeled. Half of the leaves were removed from just below the head, while the other half was removed from the middle part of the plant for each defoliation treatment (**Figure 2**). Four different defoliation treatments were

• Second treatment: A total of two leaves were removed from the plant. One of these leaves was selected from the below of the head, and the other from the middle of the plant.

• First treatment (Control): Defoliation was not carried out in this case.

The study sowing plan is given in **Figure 1**.

10 Physical Methods for Stimulation of Plant and Mushroom Development

performed. They were:

three replications.

**Figure 2.** The places from where leaves were removed in "star-shaped head stage" (from below the head and from the middle of the plant).

two, four, and six leaves removed) was carried out in the middle of the plant and from the below of the head in "star-shaped head stage," which is the beginning of the reproductive period in the plant, and the results of photosynthesis are assimilated and transported to the seeds. When the amount of assimilation produced by photosynthesis is increased, the seed

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In this study, on the effects of different defoliation treatments on seed, crude protein, and crude oil yields per decare in "star-shaped head stage," which is the beginning of the reproductive period in sunflower, it was determined that different defoliation treatments, according to cultivars, significantly increased seed, crude protein, and crude oil yields compared to

For cv. "08-TR-003," the seed yield per decare was 385.4 kg in the control treatment in which no leaf was removed, while it was 431.2 kg in the four-leaf defoliation treatment in the plant. This means that the yield increased by 11.87%. An increase of 1.90% was observed in the crude protein yield obtained from a decare. When the oil yield per decare value was examined, it was 175.0 kg for the control treatment, while it was 207.7 kg — an increase of 18.67% — in the four-leaf defoliation group. The highest values for seed, crude protein, and crude oil yields in the cv. "08-TR-003" were obtained when four leaves per plant were removed (**Table 1**).

In cv. "TR-3080," the seed yield per decare in control treatment was measured as 398.3 kg, whereas there was an 8.64% increase to 432.7 kg when two leaves were removed at the beginning of the reproductive period. The protein yield was 66.2 kg in the control, whereas it increased by 6.40% up to 70.4 kg when two leaves were removed. Examining the crude oil yield per decare values, it was 184.8 kg for the control treatment, whereas it increased by 13.36% to 209.5 kg when two leaves were removed from the plant. In cv. "TR-3080," the highest values for seed, crude protein, and crude oil yields were obtained from the two-leaf

In cv. "TARSAN-1018," 407.3 kg/da seed yield determined for the control treatment was 451.6 kg/da when six leaves were removed from the plant. This indicates that in the six-leaf defoliation treatment, seed yield increased by 10.87% compared to the control. Crude protein yield per decare was found to be 75.6 kg for control treatment, while it was 85.1 kg for the six-leaf defoliation, an increase of 12.61%. The crude oil yield per decare value in the control group was 190.7 kg, while it was 215.3 kg for the six-leaf defoliation treatment, with an increase of 12.92%. In cv. "TARSAN-1018," the highest values for seed, crude protein, and

Leaves forming the surface for active photosynthesis in plants can be damaged due to environmental factors (such as storms and hail) and mechanical factors (tools and machines used in maintenance operations such as drilling and spraying). The extent of this damage is directly proportional to the amount of defoliation. In other words, as the number of defoliations increases in the plant, the agricultural characteristics decrease proportionally, based on the cultivar. This is confirmed by the lowest values for the seed yield per decare values obtained in our study for the six-leaf defoliation treatments for cvs. "08-TR-003" and

crude oil yields were obtained from the six-leaf defoliation treatment (**Table 1**).

yield will also directly increase.

defoliation treatment (**Table 1**).

"TR-3080."

the control group with no defoliation treatment (**Table 1**).

**Figure 3.** Flowering in the head (on the left) and covering the head with paper bags to protect seeds from bird's damage (on the right).

Measurements were performed in totally 30 plants (10 plants per replication) in each defoliation treatments in all cultivars. Seed yield per plant (g/plant), seed yield per decare (kg/decare), protein and oil percentages, crude protein, and crude oil yields (kg/decare) were recorded.

Experiments were arranged at "randomized complete block, split-plot" design with three replications. In the experiment, oil-type sunflower cultivars were main plots and four defoliation applications were subplots. Data were statistically analyzed by Duncan's multiple range test using "IBM SPSS Statistics 22." Data given in percentages were subjected to arcsine (√*X*) transformation before statistical analysis [6].
