Abstract
This study compared the effects of shading in individual branch orders 2 and 3 on the needle survival, growth, and reproduction of five categories of short shoots of the proximal part of wild Atlas cedar (Cedrus atlantica (Endl.) G. Manetti ex Carrière). The sun exposure did not affect the number of short shoots in the two branch orders, whereas light compared to shade only stimulates the unbranched short shoot elongation of the branch order 3. The impact of shade exposure compared to sun on the loss of needles depends on the order of branching; it is weak to order 2 and increases to higher order. This effect in the branch order 3 is achieved by a significant decrease of the fallen leaf number in the unbranched short shoot SSnr and the short shoot SS/T worn by Twigs while in the branch order 2 only short shoot SS (nr + r) loses significantly few needles. In terms of short shoot extension and needle loss, the SS/T of the branch order 3 behaves in the same way as the SS (nr + r) of the branch order 2. The shadow compared to sunlit only decreases significantly the production of pollen strobili of the branch order 2. Close relationships between short shoot extension, leaf life span, and pollen strobili production of axillary products in the proximal part of C. atlantica crown were found.
Highlights
Beyond a broad range of species, the relationship between location and the fate of axillary buds controls the branching process which is known to be a more complex event [1]. is process has been extensively addressed in many species of deciduous and conifers and a decrease in the length of the laterals has been observed from the top of the bearing shoot [1,2,3,4,5,6]
Other studies have been made on growth dynamics and morphology of annual shoots according to their architectural position in young C. atlantica [8] and have found that annual final shoot length, duration of extension, and maximum extension rate decreased with increasing branching order. e inter- and intraspecific variation of the polycyclism was found in Cedrus, to genetically discriminate between Cedrus species, and is considered a way of adaptation to adverse climatic conditions [26]
When we compare between the effect of light and darkness on the fallen leaf mean number of each short shoot type, we find that short shoot of the order 3 branches lost significantly more needles than the order 2 branches
Summary
Beyond a broad range of species, the relationship between location and the fate of axillary buds controls the branching process which is known to be a more complex event [1]. is process has been extensively addressed in many species of deciduous and conifers and a decrease in the length of the laterals has been observed from the top of the bearing shoot [1,2,3,4,5,6]. They underscore the need for further investigation of the complex controls on pollen and strobili development because it would not be possible to use this for the moment as a proxy for environmental reconstitution and cedar conservation All these studies show that branching processes and needle death of the genus Cedrus like other species depend on plant development, age, location, and environment but might be conditioned by the neighboring branch order in the proximal part of the tree. E aim of this study is to understand how light availability affects needle survival, short shoot growth, and their sexuality within an adult tree crown of Cedrus
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