No abstract

Two experiments were carried out to evaluate the potential of single‐node cuttings of potato (Solanum tuberosum) as a tool to assess genotypic differences in maturity type. Plants were exposed to different photoperiodic treatments (different photoperiods, different numbers of photoperiodic cycles), and cuttings were taken at different plant ages. Cuttings from early (and to a lesser extent also late) maturing varieties exposed to short photoperiods showed strong induction to tuberise, irrespective of plant age; the induction increased with an increase in the number of short photoperiodic cycles. The response of cuttings taken from early‐maturing varieties exposed to long photoperiods depended on plant age: cuttings showed stronger induction when mother plants were older; cuttings from late‐maturing varieties hardly tuberised after exposure to long photoperiods. The tuberisation of the cuttings did not depend on the length of the long photoperiod (18 or 24 h) or on the number of cycles of a photoperiod of 18 h. Tuberisation on cuttings did not properly reflect the tuber formation on the mother plants, although within varieties, significant correlations between tuberisation on cuttings and tuber yield per plant 9 weeks after planting were found with different numbers of photoperiodic cycles of 12 h. Our experiments show that the cutting technique cannot be used on older plants to assess the maturity type of potato varieties, as there are interactions between photoperiod, genotype, plant age and number of photoperiodic cycles, in the reflection of the degree of induction to tuberise on single‐node cuttings.

Global competition for high standard feed-food resources between man and livestock, such as industrial broilers, is a concerning problem. In addition, the low productivity of scavenger chickens in developing countries leaves much to be desired. Changing the ingredients, and therefore, the nutrient composition of feed intake by commercial fed as well as scavenger chickens seems like an obvious solution. In this study, the ability of four broiler chicken breeds to perform on a commercial versus a scavenger diet was tested. The four broiler breeds differed genetically in growth potential. A significant (P < 0.01) negative effect of the scavenger diet on the bodyweight of the fast growing breeds was found and this effect decreased with decreasing growth rate in the other breeds. These differences in bodyweight gain could not be explained by differences in nutrient digestibility but were caused by the lack of ability of the fast growing breeds to increase their feed intake sufficiently.

Aim Elevational gradients provide excellent opportunities to explore long‐term morphological and physiological responses of plants to environmental change. We determined the difference in the elevational pattern of foliar carbon isotope composition (δ13C) between lianas and trees, and assessed whether this difference arises from changes in photosynthesis or stomatal conductance. We also explored the pattern of nutrient limitations with the elevation of these two growth forms. Location The study was conducted in two mountain forests situated in the Neotropics and Palaeotropics. Time period August–September 2015 and August–October 2016. Major taxa studied Lianas and trees. Methods We conducted inventories of lianas and trees using standardized techniques along elevational gradients in Ecuador and Rwanda. We determined the values of several foliar traits including δ13C and chemical traits in dominant liana and tree species. We set up Bayesian linear mixed‐effect models to quantify the effects of elevation and growth form on each of the foliar traits , and the difference of the effect of elevation between the two growth forms (lianas and trees). Results We found consistent growth form specific divergences in foliar δ13C and carbon to nitrogen ratio (C : N) responses to elevation. While we noted a meaningful increase in foliar δ13C and C : N with elevation for trees, lianas did not exhibit such a trend. Foliar δ13C and C : N remained relatively constant for lianas along the transects. Main conclusions Lianas operate at relatively constant intrinsic water‐ and nitrogen‐use efficiencies with elevation compared with trees. Altogether, the study suggests the existence of a functional divergence of water and nutrient use strategies between lianas and trees along tropical elevational transects.