Influence of high CO2 on growth and development of rice

The CO2 concentration in the atmosphere is rising dramatically each year. Increases are certain to influence growth of C3 plants. This thesis focuses on the growth and development of rice (Oryza sativa L. cv. Jarrah).The major questions addressed in this thesis were whether elevated atmospheric CO2 concentrations would : 1/ increase grain yield where the soil was flooded or unflooded under conditions of varying phosphorus supply; 2/ change the timing of development; 3/ alter the partitioning of dry weight and nutrients between the roots and shoots; and, 4/ influence grain quality. The mechanisms underlying growth and developmental changes at elevated CO2 were also investigated. After experimentation, it is concluded that the grain yield of rice will increase as the atmospheric CO2 concentration rises even when phosphorus supplies are low. The largest response to rising atmospheric CO2 concentrations will occur under dryland conditions but increases of up to 60 per cent are likely in flooded rice. Importantly, there is likely to be a reduction in the life cycle of rice crops as the CO2 concentration rises. This would have the advantage that more crops could be sown in one season. The quality of the rice grain produced at high CO2 concentrations will also change, with milling quality appearance likely to improve. The cooked rice will be firmer. Experiments also showed that rice grown in flooded soil at different CO2 concentrations is an excellent system for investigating the control of plant growth and development, particularly the influence of hormones

Enhanced leaf elongation rates of wheat at elevated CO₂ : is it related to carbon and nitrogen dynamics within the growing leaf blade?

This paper addresses the question of whether leaf elongation rates (LER) of monocots is controlled at high atmospheric CO₂ by nitrogen (N) and/or carbohydrate concentrations in the zones of cell division and expansion in the basal meristem of growing leaf blades. Wheat (Triticum aestivum L. cv. Hartog) was grown at high N supplies at either 360 or 700 μmol CO₂ mol⁻¹ in artificially illuminated growth chambers for 30 days prior to final harvest to determine growth parameters and chemical composition of leaf blades. We particularly focused on the spatial distribution of carbon (C), N and carbohydrate concentrations along the expanding leaf blade. Elevated CO₂ accelerated LER of expanding blade (sixth leaf blade) by 32% and this factor contributed to increase in total leaf area (18%) and shoots mass (36%). N concentrations in the expanding and last fully expanded leaf blade (LFEL) were reduced by 18% and 33%, respectively, at elevated CO₂ but soluble carbohydrate concentrations were significantly increased in the expanded leaves only. N concentrations were highest in the zones of cell division and expansion of the elongating blade but were unaffected by high CO₂ and reductions in N concentration only appeared in the cell maturing zone where division and expansion had ceased. The concentration of soluble carbohydrates was greater in the cell division and expansion than in maturation zones but was unaffected by high CO₂. C concentration was also little affected by elevated CO₂ in any zone of the blade. We conclude that greater availability of soluble carbohydrates for export from the expanded to expanding blades is the driving force for accelerated LER at elevated CO₂. It is unlikely that N concentrations limited leaf growth at high CO₂ because its concentration was unaffected by CO₂ in the zones of cell division and expansion that are most sensitive to N supply

Recent trends in accelerated cheese ripening using microencapsulated enzymes

Micro encapsulation is an inclusion technique for entrapping an active substance such as enzyme into a polymeric (gelled) matrix that may be coated by one or more semi-permeable polymers, by virtue of which the encapsulated compound becomes more stable than its free form

Root and shoot factors contribute to the effect of drought on photosynthesis and growth of the C4 grass Panicum coloratum at elevated CO2 partial pressures

We examined the hypothesis that root and shoot factors influence growth responses to elevated CO2 of the C4 grass Panicum coloratum var. makarikiense cv. Bambatsi (NAD-ME malic enzyme subtype) when well watered and droughted. Plants were grown at CO2 partial pressures (pCO2) of 36 (ambient) and 100 Pa (elevated) in pot ed soil in growth chambers for 3 weeks with adequate water (day 0) before being subjected to 15 d of drought. At day 15, enhancement of shoot growth by elevated pCO2 was 70% under drought, and 44% when well watered. During the drought period, leaf CO2 assimilation rates (A) and stomatal conductance (g) (measured at 36 Pa CO2) declined after day 2, but the decline was faster at 36 Pa CO2, and by day 9, A was negligible and intercellular pCO2 had sharply increased compared with 100 Pa CO2. Changes in carbon metabolism and water relations occurred during drought and elevated CO2 generally delayed these changes. Leaf growth rates were higher at elevated CO2 at day 0 and during drought. Importantly, the decline in soil water content was slower at elevated pCO2 due to lower transpiration rates. This explained the slower decline in A, gand shoot water relations at elevated CO2 and indicates that root factors were responsible for their decline. In contrast, leaf growth rates were higher at elevated CO2, irrespective of soil water content. We conclude that both soil and leaf factors contribute to the greater growth response of P. coloratum to high CO2 under drought, and that reduced transpiration rates explains their enhanced growth

Involvement of ethylene in the morphological and developmental response of rice to elevated atmospheric CO2 concentrations

We tested the hypothesis that increased carbohydrate flux under elevated CO2 regulates accelerated development using rice (Oryzasativa L. cv. Jarrah). Plants were grown either in flooded soil or solution culture at either 360 or 700 µ L CO2L–1. Total dry mass, shoot elongation rates (SER), tiller appearance rates (TAR) and ethylene release from intact rice seedlings were measured from 5 to 42 days after planting (DAP). At maturity, shoot and sheath length, tiller number and grain mass were also measured. Elevated CO2 had a profound effect on growth, morphology and development and the effects were more pronounced during the early growth phase. Total aboveground biomass increased at elevated CO2 and this was accounted for by enhanced tiller number. Grain yield was increased by 56% under elevated CO2 mainly due to increased tiller number and hence panicle number. TAR and SER were enhanced at elevated CO2 but SER increased only untill 25 DAP. Elevated CO2 stimulated a 2-3-fold increase in endogenous and ACC-mediated ethylene release but the ACC concentration in the leaves was little affected showing that rates of ACC synthesis matched its oxidation. Inhibition of ethylene action by 1-aminocyclopropane (1-MCP) had a more pronounced inhibitory effect on ethylene release in plants that were grown at 700 as compared to 360 µ L CO2 L–1. Feeding sucrose to intact plants enhanced ethylene synthesis and these results are consistent with the hypothesis that increased accumulation of sucrose at elevated CO2 may enhance expression of genes in the ethylene biosynthetic pathway. We conclude that increase in ethylene release may be central in promoting accelerated development under elevated CO2 and this coincides with the release of auxiliary buds and accelerated rates of tiller appearance hence increased grain yield at elevated CO2

Canopy development and hydraulic function in Eucalyptus tereticornis grown in drought in CO 2 -enriched atmospheres

We report on the relationship between growth, partitioning of shoot biomass and hydraulic development of Eucalyptus tereticornis Sm. grown in glasshouses for six months. Close coordination of stem vascular capacity and shoot architecture is vital for survival of eucalypts, especially as developing trees are increasingly subjected to spasmodic droughts and rising atmospheric CO 2 levels. Trees were exposed to constant soil moisture deficits in 45 L pots (30-50% below field capacity), while atmospheric CO2 was raised to 700 μL CO2 L-1 in matched glasshouses using a hierarchical, multi-factorial design. Enrichment with CO2 stimulated shoot growth rates for 12-15 weeks in well-watered trees but after six months of CO2 enrichment, shoot biomasses were not significantly heavier (30% stimulation) in ambient conditions. By contrast, constant drought arrested shoot growth after 20 weeks under ambient conditions, whereas elevated CO 2 sustained growth in drought and ultimately doubled the shoot biomass relative to ambient conditions. These growth responses were achieved through an enhancement of lateral branching up to 8-fold due to CO2 enrichment. In spite of larger transpiring canopies, CO2 enrichment also improved the daytime water status of leaves of droughted trees. Stem xylem development was highly regulated, with vessels per unit area and cross sectional area of xylem vessels in stems correlated inversely across all treatments. Furthermore, vessel numbers related to the numbers of leaves on lateral branches, broadly supporting predictions arising from Pipe Model Theory that the area of conducting tissue should correlate with leaf area. Diminished water use of trees in drought coincided with a population of narrower xylem vessels, constraining hydraulic capacity of stems. Commensurate with the positive effects of elevated CO2 on growth, development and leaf water relations of droughted trees, the capacity for long-distance water transport also increased

Canopy development and hydraulic function in Eucalyptus tereticornis grown in drought in CO2-enriched atmospheres

We report on the relationship between growth, partitioning of shoot biomass and hydraulic development of Eucalyptus tereticornis Sm. grown in glasshouses for six months. Close coordination of stem vascular capacity and shoot architecture is vital for survival of eucalypts, especially as developing trees are increasingly subjected to spasmodic droughts and rising atmospheric CO 2 levels. Trees were exposed to constant soil moisture deficits in 45 L pots (30-50% below field capacity), while atmospheric CO2 was raised to 700 μL CO2 L-1 in matched glasshouses using a hierarchical, multi-factorial design. Enrichment with CO2 stimulated shoot growth rates for 12-15 weeks in well-watered trees but after six months of CO2 enrichment, shoot biomasses were not significantly heavier (30% stimulation) in ambient conditions. By contrast, constant drought arrested shoot growth after 20 weeks under ambient conditions, whereas elevated CO 2 sustained growth in drought and ultimately doubled the shoot biomass relative to ambient conditions. These growth responses were achieved through an enhancement of lateral branching up to 8-fold due to CO2 enrichment. In spite of larger transpiring canopies, CO2 enrichment also improved the daytime water status of leaves of droughted trees. Stem xylem development was highly regulated, with vessels per unit area and cross sectional area of xylem vessels in stems correlated inversely across all treatments. Furthermore, vessel numbers related to the numbers of leaves on lateral branches, broadly supporting predictions arising from Pipe Model Theory that the area of conducting tissue should correlate with leaf area. Diminished water use of trees in drought coincided with a population of narrower xylem vessels, constraining hydraulic capacity of stems. Commensurate with the positive effects of elevated CO2 on growth, development and leaf water relations of droughted trees, the capacity for long-distance water transport also increased

Canopy development and hydraulic function in Eucalyptus tereticornis grown in drought in CO₂-enriched atmospheres

We report on the relationship between growth, partitioning of shoot biomass and hydraulic development of Eucalyptus tereticornis Sm. grown in glasshouses for six months. Close coordination of stem vascular capacity and shoot architecture is vital for survival of eucalypts, especially as developing trees are increasingly subjected to spasmodic droughts and rising atmospheric CO₂ levels. Trees were exposed to constant soil moisture deficits in 45 L pots (30–50% below field capacity), while atmospheric CO₂ was raised to 700 μL CO₂ L–1 in matched glasshouses using a hierarchical, multi-factorial design. Enrichment with CO₂ stimulated shoot growth rates for 12–15 weeks in well-watered trees but after six months of CO₂ enrichment, shoot biomasses were not significantly heavier (30% stimulation) in ambient conditions. By contrast, constant drought arrested shoot growth after 20 weeks under ambient conditions, whereas elevated CO₂ sustained growth in drought and ultimately doubled the shoot biomass relative to ambient conditions. These growth responses were achieved through an enhancement of lateral branching up to 8-fold due to CO₂ enrichment. In spite of larger transpiring canopies, CO₂ enrichment also improved the daytime water status of leaves of droughted trees. Stem xylem development was highly regulated, with vessels per unit area and cross sectional area of xylem vessels in stems correlated inversely across all treatments. Furthermore, vessel numbers related to the numbers of leaves on lateral branches, broadly supporting predictions arising from Pipe Model Theory that the area of conducting tissue should correlate with leaf area. Diminished water use of trees in drought coincided with a population of narrower xylem vessels, constraining hydraulic capacity of stems. Commensurate with the positive effects of elevated CO₂ on growth, development and leaf water relations of droughted trees, the capacity for long-distance water transport also increased.13 page(s