Memoire Online - Agave americana L. morphological and biochemical characterization in Kasserine, Tunisia

For aged samples, the total length shows an average of 167.5 cm and 56.6 cm respectively for aged and young leaves. This considerable length is proven by Nobel (1976) and Bertrand (1959). For young samples, it is 85.32 cm and 50.2 cm for aged and young leaves. The significant difference is probably due to meristematic activity which is yet not optimum for young samples (Nobel, 1976).

For an aged sample, the basal segment is about 26.69% of the leaf's length; 44.71cm high from the bottom bow. The medium part is about 23.62% and

measures 39.57 cm. The apical segment is about 43.35% and measures 72.62 cm. for a young sample, the basal part rises 28.9 cm from the bottom which is nearly 51.06% of the leaf, medium part is 30.86% as 17.47 cm while apical part is 18.07% about 10.23 cm. Aged samples can reach 217 cm and young ones 98.17 cm. by aging, this is because of meristematic activity of leaves and the specie's nature; it is succulent, rising and stretch out (Bertrand, 1959). The fibers contained in Agave are long ones and can reach 2mm each (Han and Rowel, 1995).

Table1: Total and maximum average length of Agave americana L. in Kasserine, Tunisia

Sample Length (cm)	Total		Maximum
	Young leaf	Aged leaf	Young leaf	Aged leaf
Young	50.2	85.32
Aged	56.6	167.5	98.17	217

	Top		Medium		Bottom
	Length (cm)	%	Length (cm)	%	Length (cm)	%
Young	10.23	18.07	17.47	30.86	28.9	51.06
Aged	72.62	43.35	39.57	23.62	44.71	26.69

Length (cm)	At bottom row	At the apex
Young sample	30.82	20.85
Aged sample	66.45	32.05

The bottom is much thicker, it's where happens water accumulation as hydro potential low (Down, 1976). The thorn of the apex shows the limited transpiration of this specie so keeps water. The leaf is also highly concentrated in fibers. It's so recommended to use the bottom for any economic and industrial use because of the better efficiency.

The average weight of young samples' leaves is about 1968 g and 974 g respectively for aged and young leaves that rise to 2945 g and 1479 g for aged

samples. Despite the equal age of young leaves extracted from young and aged samples, they don't

have the same weight. This can be explained by the fact of vegetative growth and photosynthetic activity aren't optima for young samples. Their fibers aren't well constructed and concentrated in cellulose. It's more efficient to use aged samples in industries that relies on vegetative biomass.

Data reported on the chemical properties of nonwood fibers and especially Agave americana are few. This data vary greatly, studies have varied in fiber (source, age) growing time and methodology.

The three segments of the leaf show average rates respectively from bottom: 13%; 20.49% and 28.34%. It is a significant criteria to be considered to judge the efficiency of Agave in several uses; especially industrial one. It could have a bad influence on Agave's economic profitableness. In deed, Agave's profitablessness is estimated, for 1 tonne of dry material, by nearly only 206 kg of useful one.

The distinct parts of Agave's leaves show respectively an average of humidity 86.99%; 71.65%; 79.50%. The anatomy of the whole leaf is behind its important amount of water (79.38%). It contains few stomas, is covered by an impermeable wax and has thorn all along its circumference which diminishes transpiration so much. Every possible industrial use requires dehydration, this humidity rate can be a serious handicap but his juicy plant (2.5l) is so useful in human alimentation (tequila drink). Its moistness allows the high populations in arid climate as the field site. So, It gains a tolerance even desert one.

The leaf contains an average of 0.46% of ashes. The contain is for bottom 0.66%, medium part 0.4% and apex 0.34%. Ashes, which are micro and macro-elements, aren't essential components of Agave. This poor proportion is so recommended in industrial uses especially in paper mill.

From bottom to apex, pH is respectively 5.01; 5.05; and 5.96. The leaf's pH is about 5.34. its acidity causes a cutaneous irritation within manipulations. Despite its high sugar concentration (Digest, 1980), it is not recommended in livestock alimentation. Even if it provides alcoholic drinks, its acidity can be harmful for health.

Cellulose rate (%)	Vegetal material	Bottom	Medium	Apex	Leaf
	NaOH method	74.9	57.8	34	55.56
	Alcohol method	68.42	51.15	35	51.52
Average		7.66	54.47	34.5	53.54

The cellulose rate shows a significant difference between the three parts of the leaf. Basal segment is the most concentrated. In deed, it's related to the change of chemical properties associated to fibers number and growth (Han and Rowell, 1997). Polysaccharides synthesis is optimal at bottom; the fiber's growth begins by getting its definitive length then it gets thicker and cellulose charged (Person, 1987). In the industries based on cellulose extracts, it's important to avoid the apex highly lignin concentrated that disturbs.

The average rate 55.56% is considerable and is even higher than other fiber species exploited in industrial uses. From Agave, cellulose pulps can be manufactured safely.

Lock G.W. (1962) thirty years's sisal research in Tanzania Longmans, Breen and Coltd.

Mauset J.D., Kesling R. (1997) comparative anatomy of Neoraimondia roseiflora and Neocardenasia berzogania(Cactaceae) : Haseltonia, vol 5 : 37-50.

Msahli (2002) étude du potentiel textile des fibres d'Agave Americana L., thèse pour l'obtention du titre de Docteur en sciences d'ingénieur an ENSITM.

Nobel (1976) water relations and photosynthesis of a desert CAM plant, Plant physiology. Vol 58: 576-582.

Nobel P.S. (1977) water relations of flowering of Agave desrti. Botanical Gazette, vol 138: 1-6.

Person, C.J.(1987) Agronomy of grass land systems Cambridge University press,169 p.

Pfaffli I, Sisco M.,(1995). fiber Atlas Identification of Papermarketing Fibers. Springer: 290-299.

Agave americana L. morphological and biochemical characterization in Kasserine, Tunisia

3-Results and discussion