P. J. Oyarzún

Bio: P. J. Oyarzún is an academic researcher. The author has contributed to research in topics: Transpiration & Photosynthesis. The author has an hindex of 1, co-authored 1 publications receiving 92 citations.

Photosynthesis and stomatal conductance of potato leaves-effects of leaf age, irradiance, and leaf water potential.

Abstract: Potatoes (Solanum tuberosum L., cv. Bintje) were grown in a naturally lit glasshouse. Laboratory measurements on leaves at three insertion levels showed a decline with leaf age in photosynthetic capacity and in stomatal conductance at near saturating irradiance. Conductance declined somewhat more with age than photosynthesis, resulting in a smaller internal CO2 concentration in older relative to younger leaves. Leaves with different insertion number behaved similarly. The changes in photosynthesis rate and in nitrogen content with leaf age were closely correlated. When PAR exceeded circa 100 W m−2 the rate of photosynthesis and stomatal conductance changed proportionally as indicated by a constant internal CO2 concentration. The photosynthesis-irradiance data were fitted to an asymptotic exponential model. The parameters of the model are AMAX, the rate of photosynthesis at infinite irradiance, and EFF, the slope at low light levels. AMAX declined strongly with leaf age, as did EFF, but to a smaller extent. During drought stress photosynthetic capacity declined directly with decreasing water potential (range −0.6 to −1.1 MPa). Initially, stomatal conductance declined faster than photosynthetic capacity.

Coping with drought: stress and adaptive responses in potato and perspectives for improvement.

Abstract: Potato (Solanum tuberosum L.) is often considered as a drought sensitive crop and its sustainable production is threatened due to frequent drought episodes. There has been much research aiming to understand the physiological, biochemical, and genetic basis of drought tolerance in potato as a basis for improving production under drought conditions. The complex phenotypic response of potato plants to drought is conditioned by the interactive effects of the plant's genotypic potential, developmental stage, and environment. Effective crop improvement for drought tolerance will require the pyramiding of many disparate characters, with different combinations being appropriate for different growing environments. An understanding of the interaction between below ground water uptake by the roots and above ground water loss from the shoot system is essential. The development of high throughput precision phenotyping platforms is providing an exciting new tool for precision screening, which, with the incorporation of innovative screening strategies, can aid the selection and pyramiding of drought-related genes appropriate for specific environments. Outcomes from genomics, proteomics, metabolomics, and bioengineering advances will undoubtedly compliment conventional breeding strategies and presents an alternative route toward development of drought tolerant potatoes. This review presents an overview of past research activity, highlighting recent advances with examples from other crops and suggesting future research directions.

Modelling development and growth of the potato crop influenced by temperature and daylength: LINTUL-POTATO.

Abstract: A model ‘LINTUL-POTATO’ is described which bases total dry matter production on light use efficiency of intercepted light by a potato crop. The course of light interception by green leaves initially is temperature-sum dependent and is also steered by influences of daylength and temperature on assimilate partitioning. Dry matter allocation to the foliage, which determines the final length of the growing period, is determined by a daylength and temperature dependent period between emergence and tuber initiation and subsequent partitioning of dry matter to the tubers. Once the tuber daily growth rate equals total crop dry matter accumulation, no more foliage is formed and the crop senesces faster at higher temperatures. The aim of this paper is to explain effects of temperature and daylength on total tuber production from the effects of these environmental factors on the underlying processes. The relative effect of temperature on rates of emergence, light use efficiency, tuber initiation and tuber growth, and, the effect of daylength on development rate until tuber initiation are represented quantitatively. Potential tuber production at some temperature and daylength regimes is calculated exploratively and compared with results from the literature. The model can be used to simulate tuber dry matter production in specific environments and to select cultivars for such environments with suitable temperature and daylength reactions on tuber initiation and dry matter partitioning so as to maximise yields.

Chloride regulates leaf cell size and water relations in tobacco plants

Abstract: Chloride (Cl(-)) is a micronutrient that accumulates to macronutrient levels since it is normally available in nature and actively taken up by higher plants. Besides a role as an unspecific cell osmoticum, no clear biological roles have been explicitly associated with Cl(-) when accumulated to macronutrient concentrations. To address this question, the glycophyte tobacco (Nicotiana tabacum L. var. Habana) has been treated with a basal nutrient solution supplemented with one of three salt combinations containing the same cationic balance: Cl(-)-based (CL), nitrate-based (N), and sulphate+phosphate-based (SP) treatments. Under non-saline conditions (up to 5 mM Cl(-)) and no water limitation, Cl(-) specifically stimulated higher leaf cell size and led to a moderate increase of plant fresh and dry biomass mainly due to higher shoot expansion. When applied in the 1-5 mM range, Cl(-) played specific roles in regulating leaf osmotic potential and turgor, allowing plants to improve leaf water balance parameters. In addition, Cl(-) also altered water relations at the whole-plant level through reduction of plant transpiration. This was a consequence of a lower stomatal conductance, which resulted in lower water loss and greater photosynthetic and integrated water-use efficiency. In contrast to Cl(-), these effects were not observed for essential anionic macronutrients such as nitrate, sulphate, and phosphate. We propose that the abundant uptake and accumulation of Cl(-) responds to adaptive functions improving water homeostasis in higher plants.