Response of Chrysanthemum (Dendranthemagrandiflorum) Plants to Abiotic Stress

Introduction  

Plants are sessile organisms that depend on its autotrophy for energy and root system for acquisition of nutrients and water. The rigidity of plants’ cell walls provides for its turgidity and structure. In the event of injury, plants are thus incapable of mobilizing specialized cells to respond to disorders.  Plants therefore have evolved with physical barriers such as the waxy epidermal cuticle, trichomes, thorns, bark, and the other specialized structures for primary defense against environmental factors. Environmental factors can be abiotic and biotic. Abiotic disorders in plants are caused by stimulus or influence that are beyond the range of homeostatic control, either by deficiency or excess, in plants. These are caused by the non-living factors such as temperature, humidity, light intensity, nutrients, that cause deviations from the normal physiological function of the plant system. These external factors may induce chemical and/or physical changes in plants. Evidently, these disorders cannot be transmitted since their occurrence is with the absence of infectious agents. Tissue injuries in plants, however, are potential entry points for pathogens which include fungi, bacteria, and viruses. These pathogens can cause infection, and along with mechanical injury by herbivory, parasitism, are the causes of biotic disorders. The severity and duration of stress, as well as the plants characteristics: the damaged tissue, stage of development, and genotype, are factors for the plants’ response of either resistance or susceptibility. Plants’ stress resistance mechanisms include avoidance mechanism which prevents the exposure to stress. tolerance mechanism that permits the plant to withstand the stress and acclimation wherein the plant alter their physiology in response to stress (Perez-Clemente, et. al, 2013). Germination, photosynthesis, nutrient and mineral transportation, turgidity involves the necessity of water. Water shortage significantly affects these processes. Inadeaquate amount of sunlight affects the growth of plants such as etiolation or the weakening of stems due to extensive elongation in search of light.

Plants are exposed to many adverse environmental situations that can significantly affect its growth and development. Physical injury may occur in plants in the form of laceration, cuts and scrapes. And depending on its severity and duration may also affect the function of plants.

Plants play a very vital role in our ecosystem; however, plants are exposed to various environmental stresses particularly the abovementioned conditions. Hence, it is imperative to identify how plants deal with such unfavorable conditions, starting with morphological responses. This knowledge may aid in the recognition of the plants’ ability to tolerate various forms of environmental stress.

            The current work had operated with flowering Chrysantemum plants for its availability, cost-effectiveness and low maintenance which facilitates the variables that we controlled. This study was conducted within the vicinity of the Ateneo de Zamboanga University.

Therefore, the objectives of this study are as follows:

(a) to determine the morphological response of Chrysantemum plants to drought, sunlight deficiency and physical injury and to

(b) to recognize the variation in reaction of plants to different levels of physical injury.

Methodology

Acquisition of Chrysanthemum Plants

The chrysanthemum plants were gathered from Sunnyland, a garden shop located at Veterans St., Zamboanga City. Three pots of Chrysanthemum were bought all in which contains flowers already. All of these pots do have the same type of soil used for optimal growth conditions. As seen in the pictures (See Appendix A), all of the pots are containing healthy flowering chrysanthemum.

Preparation of Setups

Three controlled setups were prepared namely: A, B and C. Setup A is the control in which it receives regular watering once a day and is exposed to the sunlight throughout the day. Setup B is controlled under the condition where it does not receive water but is still exposed to sunlight. Setup C is controlled in terms of depriving it sunlight by keeping it in a dark area the whole day. Water availability is like of the control.
These setups were held for 1 week to observe changes and the rate of the plants’ ability to regenerating from the wounds that will be done on them.

Plant Wounding

The plants were wounded 1 stem of each setup with the use of scalpel. The wounds have the dimension of 2.54cm x 15mm. After wounding, the plants were placed to the respective setups for observation. Some leaves and bud were also detached.

Plant Observation

To evaluate the plants ability to regenerate, the following variables are observed: the time for the plant to regenerate from the wounds, growth of new buds and leaves. Over-all health of the plant will be observed as well which are: the color of the leaves and the rigidity of the stem.

Results and Discussion

Table 1. Leaves after scarring

Setup	Observations
A (control)	New leaves, greenish scabbed wound, some of the previously left flower buds are now slightly blooming, new buds, turgid stem, previous buds blossomed and abundance of leaves.
B (Water Deficient)	No new leaves, no new buds, brownish scabbed wound, stem is still turgid, flowers and leaves that were left are withered.
C (Sunlight Deficient)	No new leaves, no new buds, whitish scabbed wound, still turgid, flowers that were left attached are slightly withered, some of the leaves are withered, buds that were left attached are now slightly in bloom.

Table 2.Plants before scarring.

Setup A as our control group was treated with regular watering and sunlight. The scarring was done on the stem and some of the leaves were detached from the stem as well as some flower buds. These will demonstrate how the plant will recover with the injuries inflicted as well as the abiotic stress in which they were exposed to. The control group with no abiotic stress has been able to regenerate as early as the third day of the experiment. The plant is still turgid with the flowers that were left during the experiment still blooming. The plant’s injury has now been scabbed over with slight green pigmentation. The plant has grown new leaves over the experiment week.

            Setup B faces the abiotic stress of water deficiency. It receives the same amount of sunlight with setup A. The injury was also done on the plant’s stem. Some of the leaves and flower buds were also detached from the plant to observe its physiological response. Though the plant is still turgid, it did not develop new leaves and buds. The flowers and leaves that were remained attached during the experiment have now withered but still green.

            Setup C was placed inside a cabinet and was deprived of any sunlight but is receiving the same amount of water with setup A. The plant’s injury is also on the stem and some of its leaves and flower buds were also detached before the experiment. The plant, though sunlight deficient,

Table 3. Plants after scarring

Setup	Results after scarring
Setup A (control)
Setup B (Water Deficient)
Setup C (Sun Deficient

is still turgid and has slightly became lighter green. Some of the leaves that were remained attached have withered and became brown. The remaining leaves became lighter green. The plant’s injury is now covered with a whitish scab. The flower buds left in the plant have now slightly bloomed.

            The metabolism of the plants that were exposed to abiotic stress for a week is still functioning to instill the plants’ survival. In our experiment, it is safe to say that plants, particularly the Dendranthemagrandiflorum, still functions its physiological processes in terms of regenerating new cells to recover wounded or damaged ones. Even with a deficiency in one of the abiotic factors they need to survive, the plants struggled to live. It is remarkable that the plant with sunlight deficiency still had some of its leaves intact. It basically tried to survive on water only. While this plant made some growth even under stress, the plant that experienced water deficiency is dying. All of its leaves are withered and it seems like they won’t be able to make their own food until they grow new leaves.

Conclusion

            Stress can affect the physiologicalmechanism of plantsto heal injuries based on the morphological responses observed in the experiment. Control plants have no changes in color, leaves and flowers still upright. The injuries have healed with brown color at the boundary while yellow to white as it nears the center.Sunlight deprived plants changes color from green to yellow green. The injuries made healed but there are no visible brown color at the boundary and has the color of white as it nears the center. The leaves are still upright but the flowers are slightly withered. Water deprived plants have flowers and stem are both withered. The injuries made have brownish color and yellow to white color as it goes near the center.

            Comparing the three groups it is then concluded that water deficient does not affect the healing process of plants but does affect in the overall growth of plants.Sunlight affects the pigment in the healing process of the plants as well as the color of plant’s stem and leaves. Since this study is based more on the observations of the morphological growth, this is recommended for further study based on biochemical level.

References:

FangWeiMin (2009).Effect on abiotic stress tolerance of grafting in chrysanthemum and cultivated techniques for cutting chrysanthemum. Retrieved from: http://www.dissertationtopic.net/doc/1486026

Leon, Jose, E. Rojo & J. Sanchez-Serrano. (2000). Wound Signalling in Plants. Journal of Exprimental Botany, 52(354), 9 pages.http://jxb.oxfordjournals.org/content/52/354/1.long#sec-1

Perez-Clemente, Rose, V. Vives, S. Zandalinas, M. Lopez-Climent, V. Munoz & A. Gomez-Cadenas. (2013). Biotechnological Approaches on Studying Plant Responses to Stress. BioMed Research International, Volume 2013, Article ID 65410, 6 pages. http://www.hindawi.com/journals/bmri/2013/654120/



Researchers: 
Ballos, Frances Alexandra R.
Fidel, Pjey G.
Garcia, Jayvalikka A.
Jaugar, Joyce Cedrine R.

BS Biology III

Affiliations:
Ateneo de Zamboanga University