Debergh, P., Harbaoui, Y. and Lemeur, R. 1981. Mass propagation of globe artichoke {Cynara scolymus}: Evaluation of different hypotheses to overcome vitrification with special reference to water potential. -Physiol. Plant. 53: 181-187.In search of a technique for rapid clonal propagation and sanitation of Cynara scotymus L. we have been confronted with the problem of vitrification. We only succeeded in overcoming this problem by raising the agar concentration of our medium to 1.1% instead of 0.6%. By using the Cbardakov-method and direct measurement of the water potential with a thermocouple psychrometei we were able to prove that this result was attributable to the matric potential.Additional key-words: Agar.

An investigation was carried out during three crop growing seasons (2005; 2006 and 2007) at the Technical Center of Potato (CTP) situated in the low valley of Medjerda river at Saida (Tunisia) to find out how potato and bean can grow and develop in an intercropping system rather than in sole cropping. Crop productivity of potato and bean intercropping systems was evaluated in terms of total dry matter production. The light interception and radiation use efficiency by this system were calculated in sole cropping and intercropping. Results showed that the total dry matter production (TDM) by potato in sole intercropping was higher than in sole cropping. This increase occurred during the three experiments from 3.60 to 4.75% compared to the potato in sole cropping. However, for bean in sole intercropping the TDM was significantly lower (P < 0.05) than in sole cropping. This decrease had varied from 48.9 to 63.1%. Intercropping potato with bean had actually reduced the radiation interception by both crops. This reduction was in the three experiments (2005; 2006 and 2007), respectively equal to (20.9; 9.4 and 4.8%) for potato and equivalent to (50.4; 58.7 and 44.8%) for bean. Radiation Use Efficiency for potato in sole intercropping has improved from 7.7 to 23.6%.

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This experiment was carried out at the Technical Center of Potato (C.T.P) situated in the low valley of Medjerda river at Tunisia, during two growing seasons (2006-2007) and (2008-2009). It aims at evaluating the effect of intercropping potato (Solanum tuberosum cv. Spunta) and sulla (Hedysarum coronarium L. cv. Bikra 21) grown under 1:1 intercropping row arrangement and sole cropping on water consumption and water use efficiency of one potato variety and one sulla variety. In addition, land equivalent ratio (LER) was determined to assess the efficiency of the intercropping system. Intercropping had no significant effect on the above parameters and tuber dry biomass production of potato and sulla. However, it increased the total dry biomass of the intercropping system. This increase occurred during the two cultivating seasons of 2007 and 2009 respectively from 12.5 to 14.8% compared to the potato in sole cropping. Intercropping has led to a similar reduction of water consumption (WC) of both crops. This reduction was 36 and 28% for 2007 and 2009 seasons respectively and for both crops. However, intercropping has led to an increase in the overall (WC) of the mixed system by 9.1 and 13.8% in 2007 and 2009 respectively. Water Use Efficiency (WUE) has been improved from 35.4 to 45.6% for potato in sole intercropping and from 25 to 37.5% for sulla intercropped. The values of total LER were higher than one, which indicates the superiority of intercropping system over the sole cropping system.

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