Photosynthesis and Water Relations in Brazilian Sugarcane

Sugar Tech, 2010

Phytomass production is a result of physiological processes occurring at plant canopy level, with canopy architecture affecting the availability of solar radiation to photosynthesizing tissues. The aim of this study was to identify a possible association between light availability, canopy photosynthesis and plant growth in three sugarcane varieties under field conditions. As a hypothesis, higher canopy photosynthesis and plant growth are probably found in sugarcane varieties with higher light availability at bottom canopy positions. Measurements of diurnal course of leaf gas exchange were taken in two canopy positions of the sugarcane varieties IACSP93-2060, IACSP95-3028 and IACSP95-5000, maintaining the natural leaf inclination. All sugarcane varieties exhibited similar values of diurnal CO 2 uptake at the upper canopy position. On the other hand, the bottom canopy position had an important role on photosynthesis of IACSP95-3028 sugarcane, with slight changes in leaf inclination causing significant variation of photosynthetic active radiation at the bottom canopy positions. High light availability at the bottom canopy position of IACSP95-3028 caused increased photosynthesis and improved plant vegetative growth, given by increases in tillering, leaf area and leaf and stalk phytomass accumulation.

The objective of this study was to determine the effects of soil moisture deficits on growth, physiology and yield of sugarcane varieties to identify drought tolerant varieties and specific traits. The experiment was conducted in 2002/03 at Sugarcane Research Institute, Sri Lanka (6 o 21'N, 80 o 48'E). Eight commercial varieties were grown under irrigated (soil water potential >-0.05 MPa) and rainfed conditions. Vegetative growth, cane yield and yield components, stomatal conductance and transpiration rates, root length densities at different depths of the soil were measured. The improved Sri Lankan variety, SL88-116, showed the highest cane and sugar yields under both water regimes. Cane yields of all varieties under irrigation were significantly (P<0.05) greater (38%-74%) than under rainfed conditions. High levels of stalk weight, leaf area index at harvest and the number of stalks per ha were correlated well with yields and varied for different varieties under rainfed conditions. Water conservation through lowering stomatal conductance, both at the individual leaf and canopy level, and developing higher root length densities in the 30-60 cm soil layer to survive during the periods of significant water deficits in the top soil layer (0-30 cm) were identified as mechanisms responsible for achieving high sugarcane yields in the rainfed environments of Sri Lanka.

Functional Plant Biology

Photosynthesis and growth are dependent on environmental conditions and plant developmental stages. However, it is still not clear how the environment and development influence the diurnal dynamics of nonstructural carbohydrates production and how they affect growth. This is particularly the case of C4 plants such as sugarcane (Saccharum spp.). Aiming to understand the dynamics of leaf gas exchange and nonstructural carbohydrates accumulation in different organs during diurnal cycles across the developmental stages, we evaluated these parameters in sugarcane plants in a 12-month field experiment. Our results show that during the first 3 months of development, light and vapour pressure deficit (VPD) were the primary drivers of photosynthesis, stomatal conductance and growth. After 6 months, in addition to light and VPD, drought, carbohydrate accumulation and the mechanisms possibly associated with water status maintenance were also likely to play a role in gas exchange and growth reg...

Plant Production Science

Global climate change will result in extreme environments, such as droughts and floods. We investigated the individual and combined effects of droughts and floods of varying duration on sugarcane (Saccharum spp.) growth using a pot experiment under glasshouse conditions with the following six treatments: drought for 15 d, prolonged drought for 30 d, flood for 15 d, prolonged flood for 30 d, short flood followed by prolonged drought, and prolonged flood followed by prolonged drought. Plants that were subjected to drought conditions, including drought after a flood, had reduced CO 2 assimilation (through stomatal closure) and leaf areas, whereas flood conditions showed no effect. During flooding, some roots died, and adventitious roots with welldeveloped aerenchyma appeared from the submerged nodes. At the time of harvest, there were no significant differences in stem fresh weight, sucrose content, or sugar yield between the treatments. However, ion content analysis revealed that flood conditions caused an accumulation of sodium in the bottom of stems and adventitious roots. Therefore, under flood conditions, plants may develop adventitious roots, which may offset the negative effects of root death, helping them to maintain their growth and yield. ABBREVIATION A, co 2 assimilation; dat, days after treatment; F + Pd, flood follow by prolong drought; PF + Pd, prolong flood follow by prolong drought; la, leaf area; hr, hour; d, day; mo, month; wk, week

Plant Biotechnology, 2012

Seven sugarcane (Saccharum sp.) commercial cultivars, viz., , originally derived from meristem cuttings were subjected to simulated osmotic stress (as 200 mM mannitol) under controlled environmental conditions. Proline content in the leaf tissues of all cultivars except K92-80, increased in plants subjected to mannitol-induced osmotic stress. Chlorophyll a (Chl a ), chlorophyll b (Chl b ), total chlorophyll (TC), maximum quantum yield of PSII (F v /F m ), and photon yield of PSII (Φ PSII ) of all seven cultivars decreased under osmotic stress resulting in a reduction in net-photosynthetic rate (P n ). A positive correlation was found between F v / F m and Φ PSII , proline content and non-photochemical quenching (NPQ), Φ PSII and P n , and P n and plant dry weight in the sugarcane cultivars. Based upon Ward's multivariate cluster analyses of data for proline content, photosynthetic capacity, chlorophyll fluorescence, and growth inhibition, three cultivars (K88-92, K92-80 and UT-94-2-483) were identified as water deficit sensitive, whereas four (K84-200, K95-84, K97-32 and LK92-11) as water deficit tolerant. These observations on different cultivar's sensitivity/tolerance were confirmed by growth and yield attributes measured in a field trial. The plant dry weight (in vitro) correlated positively with total stalk weight of sugarcane cultivars

The C 4 plant sugarcane (Saccharum sp. Lin-naeus) is a chilling-sensitive crop grown at low latitudes for refined sugar and bioenergy. As a leading source of sugar and feedstock for bioethanol production, there is interest in cultivating it at higher latitudes and elevations where sub-optimal temperatures are common. To assess its potential for photosynthetic acclimation to temperature, we compared photosynthetic temperature responses of lowland and upland Hawaiian sugarcane cultivars grown at 32/26 and 21/18 °C day/night temperature. The temperature response of net CO 2 assimilation rate (A) of the cultivars was similar in both treatments, with the exception that short-term exposure to 45 °C greatly inhibited A in the 21/18 °C-grown plants of both varieties when subsequently measured below 21 °C. Plants grown at 32/26 °C exhibited a modest inhibition of A below 21 °C following a 45 °C exposure. Little variation between the cultivars was observed in their responses to intercellular CO 2 partial pressure and light at varying temperatures. We thus conclude sugarcane does not exhibit a strong thermal accli-mation response at moderately sub-optimal to supra-optimal temperatures, but will acclimate to warm growth conditions in a manner that increased tolerance of heat; however, the heat intolerance was manifested as reduced performance at cooler temperatures. This could be problematic in growing regions such as the southeastern USA and China where springtime conditions can include hot days followed by strong cold fronts that brings sub-optimal temperatures.

ACS Omega

Sufficient water and fertilizer inputs in agriculture play a major role in crop growth, production, and quality. In this study, the response of sugarcane to limited water irrigation and foliar application of potassium salt of active phosphorus (PSAP) for photosynthetic responses were examined, and PSAP's role in limited water irrigation management was assessed. Sugarcane plants were subjected to limited irrigation (95−90 and 45−40% FC) after three months of germination, followed by a foliar spray (0, 2, 4, 6, and 10 M) of PSAP. The obtained results indicated that limited water irrigation negatively affected sugarcane growth and reduced leaf gas exchange activities. However, the application of PSAP increased the photosynthetic activities by protecting the photosynthetic machinery during unfavorable conditions. Mathematical modeling, a Skewed model, was developed and compared with the existing Gaussian model to describe the photosynthetic responses of sugarcane leaves under the limited irrigation with and without PSAP application. The models fitted well with the observed values, and the predicted photosynthetic parameters were in close relationship with the obtained results. The Skewed model was found to be better than the Gaussian model in describing the photosynthetic parameters of plant leaves positioned over a stem of limited water irrigation and applied PSAP application and is recommended for further application.

Sugarcane bioethanol — R&D for Productivity and Sustainability, 2014

The photosynthetic process consists of two couple reaction. The first, called photochemical phase, refers to the reactions related to light capture, electron transport and the formation of reducing power (i.e. NADPH and ATP). The second phase is the biochemical, where carbon dioxide (CO 2) is captured and transformed into compounds that link carbon atoms together and therefore retain the energy absorbed by the light reaction (BUCKERIDGE et al., 2008). In the photochemical reactions, the light captured by leaves is capable to provoke changes in chlorophyll molecules present in the chloroplasts and these changes start the transportation of electrons

In Australia water stress is estimated to cost the sugar industry an average of $260 million (AUD) per annum in lost production. With the predicted increased frequency of drought events the industry is now considering breeding for drought adaptation after water stress inflicted yield losses of more than $400 million in the years 2002–2004, in one region alone. Defining drought adaptation broadly, including both short and long periods of water stress, we took the first step in improving sugarcane for such conditions by assessing the potential benefits of a number of traits in a simulation study. The APSIM-Sugarcane model was used to simulate the biomass yield response to traits that may confer adaptation to drought in a range of climates, some extremely dry at times, and in a shallow and a deep soil. Among the traits studied, increased rooting depth resulted in 0–21% increase in mean dry biomass yield depending on the climate and soil type. This trait was more beneficial in the shallow than the deep soil which had a smaller fraction of additional stored water to offer the more vigorous root system. The simulations showed that breeding for reduced stomatal or root conductance (conductance) would increase biomass yield by about 5% only in the driest climates and better soils. Other traits which conserved water such as leaf and stalk senescence were generally unsuccessful in conferring adaptation to the water-limited production environments considered. Simulations indicated that increased transpiration efficiency (TE) at the leaf level would nearly always help to improve sugarcane biomass yields in water-limited environments if the increased TE arose from up-regulation of intrinsic water use efficiency. However if increased TE was increased through reduced conductance, which effectively reduces VPD during transpiration, yields could be reduced in high rainfall climates and shallow soils and they could increase in moderate rainfall climates and deeper soils. Thus increased rooting depth, increased intrinsic water use efficiency and to a lesser extent, reduced conductance leading to increased TE, are suggested as the best traits to consider for selection of sugarcane clones in water-limited environments in the tropics and sub-tropics.

Journal of Experimental Botany, 2015

Stomatal conductance (g s) and canopy temperature have been used to estimate plant water status in many crops. The behaviour of g s in sugarcane indicates that the internal leaf water status is controlled by regular opening and closing of stomata. A large number of g s measurements obtained across varying moisture regimes, locations, and crop cycles with a diverse sugarcane germplasm composed of introgression, and commercial clones indicated that there is a high genetic variation for g s that can be exploited in a breeding programme. Regardless of the environmental influences on the expression of this trait, moderate heritability was observed across 51 sets of individual measurements made on replicated trials over 3 years. The clone×water status interaction (G×E) variation was smaller than the clone (G) variation on many occasions. A wide range of genetic correlations (r g =-0.29 to 0.94) between g s and yield were observed across test environments in all three different production regions used. Canopy conductance (g c) based on g s and leaf area index (LAI) showed a stronger genetic correlation than the g s with cane yield (tonnes of cane per hectare; TCH) at 12 months (mature crop). The regression analysis of input weather data for the duration of measurements showed that the predicted values of r g correlated with the maximum temperature (r=0.47) during the measurements and less with other environmental variables. These results confirm that the g c could have potential as a criterion for early-stage selection of clones in sugarcane breeding programmes.