Submitted to: African Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2014
Publication Date: 11/30/2014
Citation: Jarret, R.L. 2014. Observations on anatomical aspects of the fruit, leaf and stem tissues of four Citrullus spp. African Journal of Plant Science. 8(11):521-527.
Interpretive Summary: The genus Citrullus contains four species, one of which includes the cultivated watermelon (Citrullus lanatus). The genus also contains three other species, related to the watermelon, that are native to extremely hot and dry desert environments and that are recognized as drought-tolerant. This study examined various characteristics of the stems, leaves and outer layer of the fruit tissues of watermelon and its related species in order to examine characteristics that may be associated with drought-tolerance in those spp. Differences in leaf thickness, the structure of the fruit outer cell layer(s) and the stem tissues of the carious species were detected. Further study will be required to relate these differences to drought-tolerance.
Technical Abstract: Morphological characteristics of the fruit, stem and leaf tissues of four species of Citrullus (L.) Schrad. were examined using standard histological methods. Plant materials included the cultivated watermelon (C. lanatus (Thunb.) Matsum. & Nakai) and three of its related species; C. colocynthis (L.) Schrad., C. ecirrhosus Cogn. and C. rehmii de Winter. Variation among the species was observed in the thickness of the subepidermal layer of the fruit, being considerably thicker in fruit of C. ecirrhosus (~ 200 uM) than in fruit of C. lanatus (~100 uM), C. colocynthis (~100 uM) or C. rehmii.(~ 100uM). Variation was also observed in the extent and organization of the subtending sclerenchymatous cells reaching up to 10 cell layers thick in fruit of C. colocynthis, 1 or 2 cell layers thick in fruit of C. lanatus., and an intermediate number of layers in C. ecihhosus and C. rehmii. A greater degree of lignifications in the stem tissue of C. colocynthis and C. ecirrhosus was observed, in comparison with C. lanatus and C. rehmii. Leaf thickness (~ 250 uM) was similar among three of the four species examined, but was noticeably reduced in C. rehmii (~150 uM). Further study is required in order to assess the contribution of these, and other, morphological attributes, for their potential contribution to drought tolerance in members of this genus.