Seyed Mohsen Hosseini*, Shaiesteh Gholami** and Ehsan Sayad***

*Associate Professor

**PhD Candidate

Tarbait Modares University. Natural Resources Faculty. Emam St. Noor, 46414, Noor, Mazandaran, IRAN

***Academic Staff

Natural Resources Faculty of Shahid Chamran University. Behbahan, Khozestan, IRAN

Abstract. The effect of weed competition, Planting time and Depth on growth and survival of Pistacia atlantica seedlings was evaluated in nursery conditions. Pistacia atlantica is a deciduous tree species that belongs to the Anacardiaceae family. It is valuable for soil conservation and therefore suitable for plantation in dry lands. Regeneration of Pistacia atlantica in western part of Iran presents problems due to much destruction of its natural habitats. Two levels of weed treatment (weed competition was removed several times by hand or the weeds permitted to grow) and three levels of sowing date (9 January, 29 January, 18 February) were used. In addition, seeds were sown at three different depths (0.4 and 8 cm) but no seedlings emerged when seeds were sown at 0 cm sowing depth. At the end of the first growing season on September 2004, survival, height above the soil surface, collar diameter, shoot/root length ratio and shoot/root dry weight ratio were measured. Survival was significantly affected by sowing depth but not by sowing date and weed treatment. Survival was greater at 4 cm than at 8 cm sowing depth. Collar diameter was significantly greater at 4 cm than at 8 cm sowing depth and in 9 January and 29 January than in 18 February sowing date but was not different between weed treatments. Shoot/root length ratio and height was not affected by sowing date, sowing depth and weed treatment. Shoot/root dry weight ratio was significantly lower at 4 cm sowing depth but not affected by sowing date. This ratio was greater in weed competition condition. In general weed treatment, sowing date and sowing depth are factors that can influence physical and morphological traits of seedlings.

Key words: seedling; sowing depth; sowing date; weed competition; survival; growth; nursery

Efeito da Competição de Ervas Daninhas, da Época e Profundidade da Sementeira sobre Plantas Jovens de Pistacia atlantica num Viveiro Mediterrânico no Irão

Sumário. Avaliaram-se, em viveiro, os efeitos da competição de ervas daninhas, época e profundidade de sementeirs, sobre o desenvolvimento e sobrevivência de plântulas de Pistacia atlantica. A Pistacia atlantica é uma árvore de folha caduca que pertence à família Anacardiaceae. É uma espécie muito importante, valiosa para a conservação do solo, e portanto apropriada para a plantação em regiões secas. A regeneração da Pistacia atlantica na zona oeste do Irão é problemática, devido à destruição dos seus habitats naturais. Foram estudados dois níveis de tratamento de infestantes (removidas manualmente várias vezes ou deixadas crescer) e três datas de sementeira (9 e 29 de Janeiro, e 18 de Fevereiro). Além disso, as sementes foram semeadas a três profundidades diferentes (0, 4 e 8 cm). A 0 cm não houve germinação. No final da primeira estação de crescimento em Setembro de 2004, contabilizou-se a sobrevivência e mediu-se a altura, diâmetro do colo, relação altura/comprimento da raiz e altura/peso seco da raiz. A sobrevivência foi significativamente afectada pela profundidade da sementeira, mas não pela data de sementeira e controle de infestantes. A sobrevivência foi maior com a sementeira a 4cm de profundidade do que a 8 cm. O diâmetro do colo foi significativamente maior com a sementeira a 4cm de profundidade do que a 8 cm, e para 9 e 29 de Janeiro por comparação com a da data de 18 de Fevereiro, mas sem diferença relativamente aos tratamentos das ervas. A razão altura/peso seco da raiz foi significativamente menor na sementeira a 4 cm, mas não foi afectada pela data da mesma. Esta relação aumentou no caso de competição com as infestantes. Em geral a concorrência das infestantes, data e profundidade de sementeira são factores que podem influenciar os caracteres físicos e morfológicos das plântulas.

Palavras-chave: plantas jovens; Profundidade da sementeira; época da Sementeira; Competição de ervas daninhas; sobrevivência; crescimento; viveiro

Résumé. Les effets de la concurrence de l'herbe, du periode et de la profondeur de la plantation ont été évalués sur la croissance et la survie des jeunes plantes de Pistacia atlantica dans une pépinière. Pistacia atlantica est un arbre feuillu qui appartient à la famille des Anacardiaceae. Cette espèce est très importante, car elle conserve le sol et est ainsi appropriée à la plantation dans les régions sèches. La régénération de Pistacia atlantica à l'ouest de l'Iran a des problèmes dus aux destructions de ses habitats naturels. Deux niveaux de traitement d'herbe (les herbes ont été enlevées plusieurs fois à la main ou laissé se développer) et trois niveaux de date d'ensemencement (le 9, le 29 janvier, le 18 février) ont été étudiés. En plus, des graines ont été semées à trois profondeurs différentes (0, 4 et 8 cm). Aucunes plantes n'ont émergé à la profondeur d'ensemencement 0 cm. À la fin de la première saison de croissance en septembre 2004, la survie, la taille au-dessus de la surface du sol, le diamètre de collier, le rapport de longueur et poids sec de pousse/racine ont été mesurés. La survie a été significativement affectée par la profondeur d'ensemencement mais rien par la date d'ensemencement ni le traitement de l'herbe. La survie était plus importante pour la profondeur d'ensemencement à 4 centimètres qu'à 8 centimètres. Le diamètre de collier était considérablement plus important à 4 centimètres de profondeur d'ensemencement qu'à 8 et plus important pour l’ensemencement aux 9 et 29 janvier qu'au 18 février, mais elle n'était pas différente entre les traitements d'herbe. Le rapport de longueur de pousse/racine et la taille n'ont pas été affectés par la date ni par la profondeur d'ensemencement ni par le traitement d'herbe. Le rapport de poids sec de pousse/racine à 4 centimètres de profondeur d'ensemencement était significativement inférieur aux autres profondeurs mais n’a pas été affectée par la date d'ensemencement. Ce rapport était plus important dans les conditions de traitement d'herbe. En général, la concurrence d'herbe, la date et la profondeur d'ensemencement sont des paramètres qui peuvent influencer les caractères physiques et morphologiques des jeunes plantes.

Mots clés: jeune plante; profondeur d'ensemencement; date d'ensemencement; concurrence d'herbe; survie; croissance; pépinière

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Entregue para publicação em Setembro de 2006

Aceite para publicação em Fevereiro de 2007