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Anatomical changes of cucumber (Cucumis sativus L.) leaves and roots as influenced by shade and fertigation.

Introduction

Cucumber (Cucumis sativus. L.) is an important and commercially popular cucurbitaceous vegetable crop which holds a very coveted position in the vegetable market. The crop, native to India, is one of the most nutritive vegetables rich in vitamins and minerals such as phosphorus, potassium, calcium and iron. It is mainly grown for its fruits both in tropics and subtropics of the world and produces tender fruits continuously.

Unlike the other cucurbits, cucumber fruit is commonly harvested while still green or in immature tender stage. Cucumber is not only consumed as cooked vegetable but also used as a ripe fruit. The immature tender fruits are eaten as vegetable, either salad, cooked, or made into pickled cucumbers. The flesh of cucumbers is primarily composed of water but also contains ascorbic acid (vitamin C) and caffeic acid, both of which help soothe skin irritations and reduce swelling. Hard fruit skin is rich in fiber and contains a variety of beneficial minerals including silica, potassium and magnesium. It is said to have cooling effect and prevents constipation. Cucumber is very sensitive to fluctuations of light and temperature. Hence, to understand the influence of micro environment on growth of cucumber, this investigation was carried out under 35 per cent shade net condition and anatomy of the leaves and roots were studied.

Materials and methods

In order to study the ultra structural change in the leaf, root under shade and open conditions, microtome study was taken up and anatomical observations were carried out under microscope following the method suggested by Johansen (Kadam, J.R., 1990).

Killing and Fixing

The specimens were killed and fixed in FAA for minimum 24 hours (FAA: 10:50:5:35 proportion of formalin, alcohol, acetic acid and water).

Dehydration

After killing and fixing the materials in FAA solution, they were washed with 50 per cent ethanol and then transferred to tertiary butyl alcohol series of 60, 70, 80, 90 and 100 per cent for one hour followed by 12 hours in 100 per cent tertiary butyl alcohol (TBA).

Infiltration with Wax

After the process of dehydration, they were transferred to TBA + wax series of 2/3 + 1/3, 1/2 + 1/2, 1/3 + 2/3 and absolute wax two times for 30 to 45 minutes in each series.

Embedding

Next to infiltration process, the material was embedded in wax with melting point of 52 - 54 C. For this, molten wax was poured into a paper N boat, with inner side smeared with glycerin. The infiltrated pieces were placed in molten wax in the proper orientation. The blocks were cut in such a way that each block contained one section.2.

Sectioning

The paraffin embedded specimens were sectioned with the help of rotary microtome. The thickness of the sections was 10-12 [micro]m.

Dewaxing and Staining

Dewaxing of the sections was by customary procedure suggested by Johansen (Kadam, J.R., 1990). The sections were stained with toluidine blue as per them method of O'Brien et al.. Since toluidine blue (Priyadarsan, V. and R. Naidu, 1992) is a polychromatic stain, the staining results were remarkably good; and some cytochemical reactions were also obtained. The dye rendered pink colour to the cellulose walls, blue to the lignified cells, dark green to suberin, violet to the mucilage, blue to protein bodies etc. wherever necessary sections were also stained with safranin and fast--green and IKI for starch.

Mounting

Glycerine mounted temporary preparations were made for macerated / cleared materials. Powdered materials of different parts were cleared with NaOH and mounted in glycerine medium after staining. Different cell component were studied and measured

Photomicroscopy

Microscopic descriptions of tissue are supplemented with micrographs wherever necessary. Photographs of different magnifications were taken with Nikon Labphot 2 Microscopic unit. For normal observations bright field was used. For the study of crystals, starch grains and lignified cells, polarized light was employed. Since these structures have birefringent property, under polarized light they appear bright against dark background. Magnifications of the figures are indicated by the scale--bars. Descriptive terms of the anatomical features are as given in the anatomy book of (Easu, K., 1964).

Results and discussions

The anatomical study on cucumber leaves (Table 1) grown under shade net condition indicated that the leaf had thick and prominent mid rib and thin lamina (Fig 1). The leaf thickness was 1.2 mm both in the vertical and horizontal planes. The leaf lamina was 120 hum thick and had thin epidermal layer which enlarged into conical lump bearing the trichome, whereas those leaves in open condition had thick leaf lamina (Fig 2).

This difference might be due to the fact that the leaves of shade plants are thinner and richer in chlorophyll than the leaves of sun plants.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

On examining the stomatal structure in shade net condition (Fig 3), both abaxial and adaxial epidermis had stomata. The stomata were circular measuring 20 hum in diameter. All the stomata had wide stomatal pores. The trichomes were long, thick, non glandular and were abundant on the leaf lamina. However, the walls of the trichomes were long and thin and smooth while those leaves in open condition had closed aperture, with glandular and non glandular trichomes (Fig 4).

In general, plants maintained a turgid condition during the time under drip irrigation and under shade as compared to surface irrigation and open condition. In the shade condition, there is a possibility of wide opening of stomata for longer period which might have resulted in high exchange of gases. Similarly, cucumber leaves might have remained turgid and produced more leaf surface with wide opening of stomata. Thus in turgor state, it helps in absorption of more sunlight and solar radiation, which would result in higher rate of photosynthesis and increased photosynthetic capacity ultimately leading to higher dry matter accumulation in plants under shade net condition (Table 2), (Mc Williams, E.L., 1970).

[FIGURE 3 OMITTED]

[FIGURE 4A OMITTED]

[FIGURE 4B OMITTED]

Stomatal closure in response to water deficiency (Open condition) has been well established in the present investigation. During water stress periods, the stomatal aperture was shrunken more because of the severe loss in turgidity and leaf temperature. The cucumber leaves in open condition would have faced water deficit causing a fall in turgor pressure and subsequent closure of stomata, thus, reducing the rate of carbon exchange drastically and thereby reducing the photosynthetic rate also. This is in consonance with the research work of Mc Williams and Handique and (O'Brien, T.P., N. Feder, 1964) Handique (Johansen, D.P., 1940).

Physiologically, opening and closing of stomatal pores is mediated by turgor and volume changes in guard cells. The stomatal opening and closing are mediated by potassium and anion efflux from guard cells. Stomatal opening increases the volume of guard cells as a result of increase in the water content and this may be due to the difference in the water potential (o w) between guard cells and adjacent cells as reported by Priyadarshan and Naidu (Priyadarsan, V. and R. Naidu, 1992). The roots under shade net condition were 1.5 to 5.00 mm thick (Fig 5).

[FIGURE 5 OMITTED]

The roots were either diarch with two primary xylem strands or triarch with three primary xylem strands cleaving into two or three wide secondary xylem lobes. The vessels were thick walled, wide circular, with abundant tyloses occurring in clusters. The widest vessel measured upto 300 [micro]m. Comparatively, those roots in open condition induced new shoot initials that originated adventiously near the base of the axillary buds. The roots measured upto 2.50- 4.00 mm thick. The vascular cylinder had 2-4 primary xylem strands. So, the secondary xylem cleaved into two or four wide wings. The vessels were thin walled, wide circular and the tyloses occurred in random masses. The widest vessel measured upto 210 [micro]m.8.

In the present investigation, cucumber vines with fertigation under shade produced longer roots than those grown in open condition. The water stress (in open condition) has induced new root initials that originated adventiously near the base of the axillary buds. The roots samples sectioned and studied showed the shrinkage in the passage cells and collapse of the membrane (Fig 6). The microclimate that prevailed under optimum shade conditions in the cucumber crop favoured better root development compared to open condition. The root activity was decreased with increased soil moisture stress, whereas the high available soil moisture showed very intensive root system in various crops. In accordance with this anatomical result, dry weight of the root and root /shoot ratio were more under shade net condition (Table 3)

[FIGURE 6 OMITTED]

Since marked changes appeared in the anatomical features differentiating the shade net cucumber and open cucumber, it is clear that application of partial shade had significant effect in modifying the size of cells, a positive sign of increasing the growth and yield of cucumber.

References

Easu, K., 1964. Plant anatomy. John Wiley and Sons. New York., pp: 767.

Handique, A.K. and G.K. Handique, 1996. Stomatal frequency of some economically important and endangered species of lady's slipper orchids. Indian J. Plant Physiol., 1: 57-59.

Johansen, D.P., 1940. Plant Micro technique, Mc Graw Hill Book Co. Inc., New York.

Kadam, J.R., 1990. Evaluation of soil, water, plant and atmospheric parameters in relation to furrow, sprinkler and dry irrigation methods for tomato in inceptisols. Ph.D. Thesis, M.P.K.V., Rahuri.

Mc Williams, E.L., 1970. Comparative rates of 2 dark CO uptake and acidification in the Bromeliaceae, Orchidaceae and Euphorbiaceae. Bot. Gaz., 131(4): 285-290.

O'Brien, T.P., N. Feder and M.E.Mc Cull, 1964. Polychromatic staining of plant cell walls by toluidine blue-O. Protoplasma, 59: 364-373.

Priyadarsan, V. and R. Naidu, 1992. Physiological implications of water stress in cardamom. Spice India, 4(1): 11-16.

Corresponding Author: T. Sumathi, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore- 641 003. Tamil Nadu, India.

T. Sumathi, V. Ponnuswami and B. Senthamizh selvi

Faculty of Horticulture, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore- 641 003. Tamil Nadu, India.

T. Sumathi, V. Ponnuswami and B. Senthamizh selvi: Anatomical Changes of Cucumber (Cucumis Sativus L.) Leaves and Roots as Influenced by Shade and Fertigation: Adv. in Nat. Appl. Sci., 2(3): 185-192, 2008.
Table 1: Changes in the size of the cells under shade net and in
open conditions

Anatomical features Under shade net In open

Leaf 1.2 mm thick in 1.1 mm vertically
 both vertical and and 1.2 mm
 horizontal planes horizontally
Leaf lamina 120 [micro]m thick 180[micro]m thick
Epidermis and stomata 20 [micro]m in 25 x 20 [micro]m
 diameter in diameter
Trichomes 250 [micro]m width
900 [micro]m length 80[micro]m width
250-400 [micro]m
 length
Petiole 4 mm thick in 1 - 2 mm thick
 vertical plane vertically
Vascular bundle 200x400 [micro]m in 350 x 400 [micro]m
 diameter in diameter
Xylem 40- 80 [micro]m width 50 [micro]m or less
Stem Metaxylem elements Metaxylem elements
 are 90 [micro]m in are 150 [micro]m
 diameter in diameter
Root 1.5-5.00 mm width 2.5 - 4.0 mm width

Table 2: Effect of shade and fertigation on dry matter production
(g [plant.sup.-1]) in cucumber

 Winter I (2005)

Treatment Shade Open Mean

[T.sub.1] 25.66 23.31 24.49
[T.sub.1] 28.30 26.54 27.42
[T.sub.1] 28.00 27.52 27.76
[T.sub.1] 26.65 25.88 26.27
[T.sub.1] 27.88 26.14 27.01
[T.sub.1] 26.12 25.56 25.84
[T.sub.1] 26.82 26.14 26.48
[T.sub.1] 29.66 29.22 29.44
[T.sub.1] 26.58 26.16 26.37
[T.sub.1] 24.86 22.64 23.75
[T.sub.1] 22.36 23.74 23.12
[T.sub.1] 23.64 23.88 23.76
[T.sub.1] 21.89 21.56 21.74
Mean 26.00 25.30 25.65
 SEd CD (5%)
C 0.211 0.423
T 0.537 1.079
C x T 0.760 1.526

 Winter II (2006)

Treatment Shade Open Mean

[T.sub.1] 24.64 23.16 23.90
[T.sub.1] 28.16 27.88 28.02
[T.sub.1] 27.96 26.16 27.06
[T.sub.1] 26.14 25.88 26.01
[T.sub.1] 26.56 25.14 25.85
[T.sub.1] 25.88 24.64 25.26
[T.sub.1] 25.64 24.36 25.00
[T.sub.1] 31.14 30.82 30.98
[T.sub.1] 25.86 24.68 25.27
[T.sub.1] 24.16 23.38 23.77
[T.sub.1] 23.56 22.68 23.17
[T.sub.1] 24.58 24.14 24.36
[T.sub.1] 22.88 21.46 22.12
Mean 25.86 25.03 25.44
 Sed CD (5%)
C 0.118 0.236
T 0.300 0.603
C x T 0.424 0.852

 Pooled winter

Treatment Shade Open Mean

[T.sub.1] 25.15 23.24 24.19
[T.sub.1] 28.23 27.21 27.72
[T.sub.1] 27.98 26.84 27.41
[T.sub.1] 26.40 25.88 26.14
[T.sub.1] 27.22 25.64 26.43
[T.sub.1] 26.00 25.10 25.55
[T.sub.1] 26.23 25.25 25.74
[T.sub.1] 29.68 30.74 30.21
[T.sub.1] 26.22 25.42 25.82
[T.sub.1] 23.03 23.01 23.02
[T.sub.1] 24.62 23.67 23.65
[T.sub.1] 24.11 22.85 23.48
[T.sub.1] 22.21 22.28 22.75
Mean 25.93 25.16 25.55
 Sed CD (5%)
C 0.164 0.329
T 0.417 0.839
C x T 0.590 1.186

 Summer I (2006)

Treatment Shade Open Mean

[T.sub.1] 27.82 26.14 26.98
[T.sub.1] 29.72 27.64 28.68
[T.sub.1] 30.20 28.16 29.18
[T.sub.1] 32.30 30.88 31.59
[T.sub.1] 33.10 31.56 32.33
[T.sub.1] 34.45 30.54 32.50
[T.sub.1] 37.40 35.74 36.57
[T.sub.1] 39.60 38.52 39.06
[T.sub.1] 36.33 35.72 36.03
[T.sub.1] 27.52 25.14 26.33
[T.sub.1] 25.84 23.52 24.68
[T.sub.1] 26.36 25.66 26.01
[T.sub.1] 24.50 21.88 23.19
Mean 31.16 29.32 30.24
 SEd CD (5%)
C 0.141
T 0.359
C x T 0.508

 Summer II (2006)

Treatment Shade Open Mean

[T.sub.1] 28.16 27.54 27.85
[T.sub.1] 29.88 28.14 29.01
[T.sub.1] 30.64 29.72 30.18
[T.sub.1] 31.88 30.54 31.21
[T.sub.1] 32.44 31.14 31.79
[T.sub.1] 33.88 30.52 32.20
[T.sub.1] 36.56 32.84 34.70
[T.sub.1] 39.88 38.56 39.22
[T.sub.1] 36.54 35.46 36.00
[T.sub.1] 27.68 25.72 26.90
[T.sub.1] 26.14 26.14 25.93
[T.sub.1] 26.88 25.54 26.21
[T.sub.1] 25.66 24.88 25.28
Mean 31.25 29.75 30.50
 Sed CD (5%)
C 0.283 0.142
T 0.722 0.361
C x T 1.021 0.511

 Pooled Summer

Treatment Shade Open Mean

[T.sub.1] 27.99 26.84 27.42
[T.sub.1] 29.80 27.89 28.85
[T.sub.1] 30.42 28.94 29.68
[T.sub.1] 32.09 30.71 31.40
[T.sub.1] 32.77 31.35 32.06
[T.sub.1] 34.17 30.53 32.35
[T.sub.1] 36.98 34.29 35.64
[T.sub.1] 39.74 38.54 39.14
[T.sub.1] 36.44 35.59 36.01
[T.sub.1] 27.59 25.64 26.64
[T.sub.1] 25.99 24.62 25.31
[T.sub.1] 26.62 25.60 26.11
[T.sub.1] 25.09 23.38 24.24
Mean 31.21 29.53 30.37
 SEd CD (5%)
C 0.285 0.141 0.284
T 0.726 0.361 0.724
C x T 1.027 0.510 1.024

Table 3: Effect of shade and fertigation on root shoot ratio
in cucumber

 Winter I (2005)

Treatment Shade Open Mean

[T.sub.1] 26.36 20.56 23.46
[T.sub.2] 26.89 24.63 25.76
[T.sub.3] 25.14 21.36 23.25
[T.sub.4] 19.87 19.62 19.75
[T.sub.5] 22.89 20.32 21.61
[T.sub.6] 24.70 21.24 22.97
[T.sub.7] 22.45 20.26 21.36
[T.sub.8] 28.79 26.45 27.62
[T.sub.9] 24.56 21.36 22.96
[T.sub.10] 23.64 20.48 22.06
[T.sub.11] 22.36 19.68 21.02
[T.sub.12] 24.36 22.24 23.30
[T.sub.13] 19.24 18.65 18.95
Mean 23.94 21.30 22.62
 SEd CD (5%)
C 0.189 0.379
T 0.481 0.967
C x T 0.681 1.368

 Winter I (2006)

Treatment Shade Open Mean

[T.sub.1] 24.86 20.26 22.56
[T.sub.2] 26.86 24.88 25.87
[T.sub.3] 24.36 22.36 23.36
[T.sub.4] 24.63 20.14 22.39
[T.sub.5] 25.46 20.22 22.84
[T.sub.6] 23.24 20.34 21.79
[T.sub.7] 23.36 21.11 22.02
[T.sub.8] 27.45 25.46 26.46
[T.sub.9] 25.42 19.96 22.69
[T.sub.10] 23.63 20.88 22.26
[T.sub.11] 24.68 21.46 23.07
[T.sub.12] 25.66 20.33 23.00
[T.sub.13] 24.06 19.68 21.17
Mean 24.92 21.20 23.06
 SEd CD (5%)
C 0.246 0.495
T 0.628 1.261
C x T 0.888 1.784

 Pooled winter

Treatment Shade Open Mean

[T.sub.1] 25.61 20.41 23.01
[T.sub.2] 26.88 24.76 25.82
[T.sub.3] 24.75 21.86 23.31
[T.sub.4] 22.25 19.88 21.07
[T.sub.5] 24.18 20.27 22.22
[T.sub.6] 23.97 20.79 22.38
[T.sub.7] 22.91 19.97 21.44
[T.sub.8] 28.12 25.96 27.04
[T.sub.9] 24.99 20.66 22.83
[T.sub.10] 23.64 20.68 22.16
[T.sub.11] 23.52 20.57 22.05
[T.sub.12] 25.01 21.29 23.15
[T.sub.13] 21.80 19.17 20.48
Mean 24.43 21.25 22.84
 SEd CD (5%)
C 0.217 0.437
T 0.554 1.113
C x T 0.784 1.574

 Winter I (2005)

Treatment Shade Open Mean

[T.sub.1] 25.68 21.24 23.46
[T.sub.2] 27.88 25.34 26.61
[T.sub.3] 26.34 24.56 25.45
[T.sub.4] 22.36 19.63 21.00
[T.sub.5] 24.56 21.13 22.85
[T.sub.6] 25.42 22.13 23.78
[T.sub.7] 24.56 20.42 22.49
[T.sub.8] 28.24 26.46 27.35
[T.sub.9] 25.36 20.42 22.89
[T.sub.10] 24.82 21.24 23.03
[T.sub.11] 25.64 21.16 23.40
[T.sub.12] 24.23 19.69 21.96
[T.sub.13] 22.34 18.66 20.50
Mean 25.19 21.70 23.44
 SEd CD (5%)
C 0.196 0.394
T 0.500 1.004
C x T 0.707 1.421

 Winter I (2006)

Treatment Shade Open Mean

[T.sub.1] 23.66 20.96 22.31
[T.sub.2] 25.78 22.34 24.06
[T.sub.3] 25.66 21.86 23.76
[T.sub.4] 23.64 20.46 22.05
[T.sub.5] 23.46 20.58 22.02
[T.sub.6] 25.36 21.88 23.62
[T.sub.7] 23.54 21.42 22.48
[T.sub.8] 26.58 25.88 26.23
[T.sub.9] 24.86 20.46 22.66
[T.sub.10] 24.36 20.36 22.36
[T.sub.11] 23.46 20.42 21.94
[T.sub.12] 25.66 20.68 23.17
[T.sub.13] 22.38 20.24 21.31
Mean 24.49 21.35 22.92
 SEd CD (5%)
C 0.184 0.370
T 0.469 0.943
C x T 0.664 1.333

 Pooled winter

Treatment Shade Open Mean

[T.sub.1] 24.67 21.10 22.89
[T.sub.2] 26.83 23.84 25.34
[T.sub.3] 26.00 23.21 24.61
[T.sub.4] 23.00 20.05 21.52
[T.sub.5] 24.01 20.86 22.43
[T.sub.6] 25.39 22.01 23.70
[T.sub.7] 24.05 20.92 22.49
[T.sub.8] 27.41 26.17 26.79
[T.sub.9] 25.11 20.44 22.78
[T.sub.10] 24.59 20.80 22.70
[T.sub.11] 24.55 20.79 22.67
[T.sub.12] 24.95 20.19 22.57
[T.sub.13] 22.36 19.45 20.91
Mean 24.84 21.52 23.18
 SEd CD (5%)
C 0.188 0.377
T 0.479 0.962
C x T 0.677 1.360
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Title Annotation:Original Article
Author:Sumathi, T.; Ponnuswami, V.; Senthamizh selvi, B.
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Geographic Code:9INDI
Date:Sep 1, 2008
Words:3703
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