Effect of different harvest dates on growth characteristics and aloin content of Aloe barbadensis Miller.
Aloes are xerophytes in the Aloeaceae in the Liliales that approximately 400 species have been described in the genus Aloe . Aloe vera is perennial specie; its biomass is represented mainly by leaves, growth occurs in a rosette around a small portion of stem no greater than 5 cm. The leaves are simple, triangular, succulent, thick, with narrow lanceolate mucro tip, 30-60cm long, and 5-12cm wide at the base and 0.8-3cm thick . The margins of the leaves have sharp triangular teeth about 2 mm long. The main root is 4-10cm long and 4-5cm in diameter, the rhizosphere is concentrated at a depth of 15-20 cm. Flowers 2.5-3cm long, yellow, grouped in clusters on a single erect stem about 1m long. Reproduction is primarily by asexual plantlets .
Aloe Vera is an important industrially cultivated species, from which is extracted a gel of proven pharmacological and medicinal value [12,6]. The gel of A. vera possesses various biological and physiological activities in cosmetology and medicine: healing ability of skin burns and cutaneous injuries; prophylactic effect against radiation leucopenia; antiulcer; inhibitory action against some bacteria and fungi; inflammation-inhibiting effect; inhibition of the prostaglandin synthesis by anthraquinone-type compounds; and inhibition of the AIDS virus by acemannan [6,7,9].
Harvesting is a critical operation especially in leafy plants during growth . Selection of an optimal harvest date will require a better understanding of the chemical changes that occur during different stages of plant growth and development . The cultivation of aloe vera has acquired great commercial importance for medicinal products and cosmetics processing but information are scarce about agronomic management of this crop .
Since no report is available on the growth characteristics of aloe vera influenced by harvest dates, the objective of this study was to determine the effects of harvest time of Aloe barbadensis Miller. leaves on growth, yield and aloin production under greenhouse conditions.
Materials and Methods
Location and plant material
The experiment was carried out at the college of Agriculture, Tarbiat Modares University, Tehran, during 2008 and 2009 years under greenhouse conditions (35,43 N; 51,8 E; 1215 m sea level). Plants were grown in silt-loam soil, with good drainage, the characteristics of which are shown in Table 1.
Aloe vera seedlings were obtained from commercial greenhouse at the Tarbiat Modares University. All selected seedlings for planting were similar in length (25 cm) and had three or four leaves. Greenhouse temperatures during day and night were 28 and 22 C[degrees] respectively. Photosynthetic active radiation was 40 %. Plants were cultured in rows of 90 cm apart and spaced 60 cm distances between every plant in the row. Distance between plots was 1.5 m. Each plot had five rows and 30 plants. Mechanical weed control was done regularly. All agronomic management practices were performed as needed. Irrigation system was drip and repeated every 5 days during summer season and 7 days for winter. Add 100 kg/h N, 50 kg/h P and 50 kg/h K in every three months during growth period by irrigation. The treatments included before of flowering (12 months after planting), early flowering (16 months after planting) and full flowering (18 months after planting).
For harvest in each stage, five plants in any treatment were selected and five mature leaves in every plant were harvested. First, the plant height, leaf number, leaf length, leaf thickness and leaf diameter were measured. Fresh weight of leaf, peel and gel were measured by digital balance. Leaf volume was measured by immersion of leaf in full water cylinder. Gel was separate from peel by hand and both of leaf and gel inoculated in oven by 70 [degrees]C for a week. Then, leaf dry weight, peel dry weight, gel dry weight and powder yield were calculated. Gel to leaf weight and gel/peel weight were calculated. The aloin content of leaf was determined by Hplc (ppm/ 20 mg fresh wt.).
The experiment was arranged as a completely randomized design (CRD) with four replications of each treatment. Each treatment included 12 plants. All analyses were performed with a statistical software package (SPSS version 13) and the means were compared by tukey test at 5% level of probability.
The results are shown that time of harvest is important practice and had significant effect on dimension parameters of aloe vera plants (Table 2). The highest of plant height, leaf length and leaf diameter were obtained in early flowering (67.5 cm, 57.4 and 9.2 cm, respectively) and had not significant different with other treatments. Also, the highest of leaf thickness and leaf volume were obtained in early flowering (2.6 cm and 359.6 [cm.sup.3], respectively) and had significant difference in comparison with other dates. The maximum of leaf number was achieved in full flowering stage.
Plant weight and yield
The results in table 3 indicated that harvest dates had positive effects on some parameters of plant weight. Thus, highest amount of leaf fresh, leaf dry, peel fresh, peel dry and gel fresh weights were obtained in the early flowering. So that leaf fresh, leaf dry and gel fresh weight had significant difference compared to before of flowering but peel fresh and peel dry weight had not different with other dates. The maximum quantity of gel dry weight was attained in full flowering by 4.43 g and had significant different compared to before of flowering.
The results indicated that delay in harvest date had influence on powder yield, gel / leaf weight and gel / peel weight. So, from before of flowering to full flowering stages, amounts of these parameters were increased gradually (table 4).
As shown in Figure 1 harvest date significantly increased aloin content of aloe vera leaf. Maximum aloin content (415.6 ppm/ 20 mg fresh wt.) was occurred at first harvest date (12 months after planting, before of flowering). Following amounts of leaf aloin were obtained in early and full flowering dates, respectively (359.4 and 120.8 ppm/ 20 mg fresh wt.). The aloin content of leaf from the first to the third harvest, decreased about of 29.5 %.
[FIGURE 1 OMITTED]
At first harvest date (before of flowering), plants had not sufficient time for higher growth and the usage of environmental factors. But, by delay in harvest date, time duration for plant growth was increased so that it resulted in increasing the plant height, leaf length, leaf diameter, leaf thickness, Leaf volume and Leaf number and therefore resulted in rising leaf, gel weight and powder yield of aloe vera. Our results are in agreement with Amaducci and Pritoni . They found that passing from the early harvest to the late harvest root yield increased of about 16% in chicory. The first results obtained testing the yield potential of leaf aloe vera for aloin production in the greenhouse conditions appear to be of a great interest.
From the results mentioned above, it could be concluded that harvest dates had influence on plant growth, weight, yield, gel and aloin content of aloe vera leaves and is important agricultural practice for obtain the highest yield. Therefore, for increasing leaf and gel weights, selection of early flowering as best harvest date can be suggested.
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Zeinolabedin Tahmasebi Sarvestani, Department of Agronomy, College of Agriculture, Tarbiat Modares University, Tehran, Iran. E-mail: firstname.lastname@example.org
(1) Saeid Hazrati, (1) Zeinolabedin Tahmasebi Sarvestani, (2) Sadrollah Ramezani
(1) Department of Agronomy, College of Agriculture, Tarbiat Modares University, Tehran, Iran.
(2) Department of Horticulture Science, College of Agriculture, Shiraz University, Shiraz, Iran.
Saeid Hazrati, Zeinolabedin Tahmasebi Sarvestani, Sadrollah Ramezani; Effect of different harvest dates on growth characteristics and aloin content of Aloe barbadensis Miller
Table 1: Some chemical and physical characteristics of experimental soil Soil EC P depth (cm) PH (mmhos/cm) (mg/Kg) O.C (1) (%) 0-30 7.5 1.68 17 1.09 30-60 7.2 1.61 16 1.07 Soil M. N (3) Sulfur depth (cm) T.N (2) (%) (mg/Kg) K (mg/Kg) (mg/Kg) 0-30 0.09 17 433 48 30-60 0.11 19 426 45 (1.) Organic matter (2.) Total Nitrogen (3.) Mineral Nitrogen Table 2: Harvest dates effects on plant height and dimension of Aloe barbadensis Miller. plant height leaf leaf length harvest date (cm) number (cm) before of flowering 65.4 a ([dagger]) 20.9 a 54.1 a early flowering 67.5 a 23 a 57.4 a full flowering 67.2 a 23.4 a 57.2 a leaf diameter leaf thickness leaf volume harvest date (cm) (cm) ([cm.sup.3]) before of flowering 8.5 a 1.8 b 226.3 b early flowering 9.2 a 2.6 a 359.6 a full flowering 8.6 a 2 b 258.1 ab ([dagger]) Means having the different letters within a column significantly different for p = 0.05 (Tukey test). Table 3: Harvest dates effects on plant weight parameters of Aloe barbadensis Miller. leaf fresh leaf dry peel fresh harvest date weight (g) weight (g) weight (g) before of flowering 360.9 b ([dagger]) 13.7 b 104.1 a early flowering 494 a 18 a 121.9 a full flowering 403.4 ab 16.3 ab 100.2 a peel dry gel fresh gel dry harvest date weight (g) weight (g) weight (g) before of flowering 10.92 a 256.8 b 2.77 b early flowering 14.20 a 371.5 a 3.80 ab full flowering 11.88 a 303.2 ab 4.43 a ([dagger]) Means having the different letters within a column significantly different for p = 0.05 (Tukey test). Table 4: Harvest dates effects on powder yield, gel/leaf weight and gel/peel weight of Aloe barbadensis Miller. gel / leaf gel / peel harvest date powder yield (g) weight weight before of flowering 1.07 b ([dagger]) 71.22 b 2.49 b early flowering 1.02 b 75.10 a 3.03 a full flowering 1.46 a 75.17 a 3.02 a ([dagger]) Means having the different letters within a column significantly different for p = 0.05 (Tukey test).
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|Title Annotation:||Original Article|
|Author:||Hazrati, Saeid; Sarvestani, Zeinolabedin Tahmasebi; Ramezani, Sadrollah|
|Publication:||Advances in Environmental Biology|
|Date:||Jan 1, 2011|
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