Response of Bromus valdivianus (Pasture Brome) Growth and Physiology to Defoliation Frequency Based on Leaf Stage Development

first_pagesettingsOrder Article Reprints Open AccessArticle Response of Bromus valdivianus (Pasture Brome) Growth and Physiology to Defoliation Frequency Based on Leaf Stage Development by Iván P. Ordóñez 1,2,3ORCID,Ignacio F. López 1,3,*,Peter D. Kemp 1,3ORCID,Daniel J. Donaghy 1,Yongmei Zhang 4ORCID andPauline Herrmann 5 1 School of Agriculture and Environment, Massey University, Private Bag 11-222, Palmerston North 4440, New Zealand 2 Instituto de Investigaciones Agropecuarias, INIA, Kampenaike, Punta Arenas 6212707, Chile 3 Centro de Investigación en Suelos Volcánicos, Universidad Austral de Chile, Valdivia 5091000, Chile 4 Gansu Provincial Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China 5 Ecole Nationale Supérieure d’Agronomie et des Industries Alimentaires, ENSAIA, 54505 Nancy, France * Author to whom correspondence should be addressed. Agronomy 2021, 11(10), 2058; https://doi.org/10.3390/agronomy11102058 Submission received: 16 September 2021 / Revised: 8 October 2021 / Accepted: 8 October 2021 / Published: 13 October 2021 Downloadkeyboard_arrow_down Browse Figures Review Reports Versions Notes Abstract The increase in drought events due to climate change have enhanced the relevance of species with greater tolerance or avoidance traits to water restriction periods, such as Bromus valdivianus Phil. (B. valdivianus). In southern Chile, B. valdivianus and Lolium perenne L. (L. perenne) coexist; however, the pasture defoliation criterion is based on the physiological growth and development of L. perenne. It is hypothesised that B. valdivianus needs a lower defoliation frequency than L. perenne to enhance its regrowth and energy reserves. Defoliation frequencies tested were based on B. valdivianus leaf stage 2 (LS-2), leaf stage 3 (LS-3), leaf stage 4 (LS-4) and leaf stage 5 (LS-5). The leaf stage development of Lolium perenne was monitored and contrasted with that of B. valdivianus. The study was conducted in a glasshouse and used a randomised complete block design. For Bromus valdivianus, the lamina length, photosynthetic rate, stomatal conductance, tiller number per plant, leaf area, leaf weights, root growth rate, water-soluble carbohydrates (WSCs) and starch were evaluated. Bromus valdivianus maintained six live leaves with three leaves growing simultaneously. When an individual tiller started developing its seventh leaf, senescence began for the second leaf (the first relevant leaf for photosynthesis). Plant herbage mass, the root growth rate and tiller growth were maximised at LS-4 onwards. The highest leaf elongation rate, evaluated through the slope of the lamina elongation curve of a fully expanded leaf, was verified at LS-4. The water-soluble carbohydrates (WSCs) increased at LS-5; however, no statistical differences were found in LS-4. The LS-3 and LS-2 treatments showed a detrimental effect on WSCs and regrowth. The leaf photosynthetic rate and stomatal conductance diminished while the leaf age increased. In conclusion, B. valdivianus is a ‘six-leaf’ species with leaf senescence beginning at LS-4.25. Defoliation at LS-4 and LS-5 was optimum for plant regrowth, maximising the aboveground plant parameters and total WSC accumulation. The LS-4 for B. valdivianus was equivalent to LS-3.5 for L. perenne. No differences related to tiller population in B. valdivianus were found in the different defoliation frequencies.

Keywords

defoliation criterion, energy reserves, growing degree days, photosynthetic rate, stomatal conductance

Citation

Ordóñez IP, López IF, Kemp PD, Donaghy DJ, Zhang Y, Herrmann P. (2021). Response of Bromus valdivianus (pasture brome) growth and physiology to defoliation frequency based on leaf stage development. Agronomy. 11. 10.

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https://mro.massey.ac.nz/handle/10179/70446

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