Impact of changing climatic factors on physiological and vegetative growth parameters of young grafted grapevines

Theron, Hanle (2020-03)

Thesis (PhDAgric)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The establishment of a new vineyard is expensive and a high survival rate of the young vines is important to prevent re-planting and ensure that the vines come into full production as early as possible. The initial growth of the young vines is very sensitive to the environment and this has a direct effect on the performance and longevity of the vineyard. It is expected that future climatic scenarios will put additional strain on young vine growth. In this study the physiological functioning and growth of the vine during the first few months after planting were measured in simulated future conditions. Newly potted vines were investigated during their first 12 weeks of growth in a glasshouse. The same rootstock (101-14 Mgt) was used throughout with Shiraz (SH 470) and Merlot noir (MO 348) as scion cultivars. The treatment factors comprised three climatic variables with two levels each: temperature, CO2 and water. Measurements were taken at 4, 8 and 12 weeks after planting. The physiological activity, vegetative growth response, mineral uptake and translocation as well as the synthesis and allocation of metabolites to the various vine parts were investigated. High CO2 levels increased the photosynthetic activity of the young vines and improved the efficiency of water and nitrogen use, provided that water stress did not increase to severe levels. The negative effect of water deficit on physiological activity was to a certain extent mitigated by elevated CO2. Inherent phenology-linked patterns in the grapevine pertaining to shoot and root growth, nutrient uptake, metabolite synthesis, translocation and accumulation, and reserve storage were similar in the various treatments. Merlot performance and growth seemed more sensitive to water deficit than Shiraz, but Merlot was more stimulated by elevated CO2 levels. The effects of the treatment factors on macro- and micro-nutrient levels in vine tissues depended on the particular nutrient, the tissue type concerned, as well as the scion/rootstock genotype. Stronger vegetative growth was associated with lower nutrient concentrations in the tissues, but a similar (or higher) content. The results showed that the choice of the scion-rootstock combination per terroir would become increasingly important. Soil preparation depth should be maximised to enhance depth penetration of roots and improve the buffer capacity of the vines against unfavourable conditions. Irrigation strategies for young vines should be aimed at increased root growth and distribution. Any cultivation should be done with circumspection in young vineyards and restrictive growth environments to avoid competition for water and nutrients. Higher CO2 levels increased (and sustained) physiological activity and metabolism and induced stronger vegetative growth. These positive effects were further enhanced by water supply. It is suggested that irrigation and fertilisation programmes be re-evaluated, especially for young vines in the context of a changing climate where water would become less available and vegetative growth would increase as result of a higher atmospheric CO2.

AFRIKAANSE OPSOMMING: Insetkoste vir die vestiging van ‘n nuwe wingerd is hoog en dus is dit belangrik om hervestiging te beperk en die wingerd so gou moontlik in volproduksie te kry. Die aanvanklike groei van ‘n nuut aangeplante wingerd het ‘n direkte effek op langtermyn wingerdprestasie en lewensduur van die blok. Jong stokkies is uiters sensitief vir omgewingstoestande en daar word verwag dat toekomstige klimaatsomstandighede vegetatiewe groei in die eerste groeiseisoen sal beïnvloed. Hierdie studie het gefokus op fisiologiese aktiwiteit en mate van vegetatiewe groei van stokkies gedurende die eerste maande ná plant wanneer hulle aan verwagte veranderde klimaatsomstandighede blootgestel mag word. Shiraz (SH 470) en Merlot (MO 348) stokkies (met 101-14 Mgt as onderstok) is in potte geplant en vir 12 weke in ‘n glashuis gemonitor. Behandelingsfaktore was drie klimaatsveranderlikes, nl. temperatuur, CO2 en water, wat op twee vlakke elk toegepas is. Metings is 4, 8 en 12 weke na plant gedoen en daar is op fisiologiese aktiwiteit van stokkies, vegetatiewe groei, opname en vervoer van minerale, asook vervaardiging en interne verspreiding van metaboliete gefokus. Fotosintese en die doeltreffendheid van water- en stikstofverbruik het verbeter waar die stokkies aan hoër CO2 vlakke blootgestel is, mits watertekorte nie té straf was nie. Watertekort se nadelige effek op fisiologiese aktiwiteit is tot ‘n mate deur verhoogde CO2 vlakke teengewerk. Inherente patrone vir looten wortelgroei; mineraalopname; vervaardiging, vervoer en opbouing van metaboliete; asook reserwe opbouing in wingerdstokkies is nie deur die onderskeie behandelings beïnvloed nie. Merlot stokkies was meer sensitief vir watertekort as Shiraz stokkies, maar het sterker positief op ‘n verhoging in CO2 vlakke gereageer. Die effek van die behandelings op makro- en mikro-voedingstofvlakke in die onderskeie plantorgane het afgehang van die spesifieke mineraal, orgaan van toepassing en genotipe van die bo-/onderstok. Sterker vegetatiewe groei het gepaard gegaan met laer konsentrasies van minerale in die onderskeie weefsels, maar met vergelykbare (of hoër) totale minerale inhoud. Die resultate dui daarop dat die keuse van bo-/onderstok kombinasie vir ‘n spesifieke terroir in belangrikheid gaan toeneem. Gronde behoort tot maksimum diepte voorberei te word om dieptepenetrasie van wortels te verseker en die bufferkapasiteit van die wingerd teen ongunstige toestande te verhoog. Besproeiïngspraktyke moet daarop gemik wees om wortelgroei- en verspreiding by jong stokkies te bevorder. Alle verbouingspraktyke in jong wingerde (en wingerde wat blootgestel word aan beperkende groeitoestande) moet met omsigtigheid toegepas word sodat kompetisie vir water en voedingstowwe beperk word. Verhoogde CO2 vlakke het fisiologiese aktiwiteit en metabolisme van jong stokkies gestimuleer en onderhou, en het ook sterkter vegetatiewe groei tot gevolg gehad. Hierdie positiewe uitwerking op die stokkies is verder deur voldoende watervoorsiening bevorder. Dit word voorgestel dat besproeiïngs- en bemestingsriglyne herevalueer word, veral met betrekking tot jong stokkies in die konteks van klimaatsverandering, waar die beskikbaarheid van water na verwagting sal verminder en vegetatiewe groei deur die hoër atmosferiese CO2 konsentrasie gestimuleer mag word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107971
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