Enzymes can adjust to changes in the temperature environment, such that rates in acclimated plants are not as divergent as would be anticipated from the immediate response to temperature change. Acclimation can take a number of forms which may involve changes in isozymes or enzyme concentration, modification of an enzyme by substrate and effectors, or changes in metabolic regulation.
Exposure to excessive temperatures during development limits the yield of many of the world’s major crops, especially in the tropics. Increasing global temperatures over the last three decades have resulted in significantly reduced yields in many crops. In addition to the general warming, a predicted increase in the occurrence of heatwaves is likely to result in further yield losses (Long and Ort 2010). Increasing global temperatures and increasingly frequent heatwaves are likely to have similarly negative effects on natural systems in the tropics and subtropics.
BBC - GCSE Bitesize: Factors affecting photosynthesis
For many years, the inhibition of gross photosynthesis was thought to occur at temperatures too low to be explained by the thermal deactivation of photosynthetic enzymes. Experiments comparing the thermal response of many steps in the photosynthetic apparatus, suggested the initial inhibition was due to the sensitivity of the thylakoid membrane to high temperatures (Berry and Bjorkman 1980). However, this view has been questioned recently with the observation that at moderately high temperatures photosynthetic inhibition coincides with a reversible reduction in the activity of certain Calvin cycle enzymes (Sharkey 2005). Severe heat stress is still thought to be due to injury of PSII, through direct cleavage of the D1 protein and a range of other mechanisms. Although the thermal sensitivity of PSII is not solely due to the thermal sensitivity of cell membranes, membrane properties are a major regulator of both inhibition and injury of PSII (Sharkey 2005; Allakhverdiev et al. 2008).
The Effect of Light on Photosynthesis ..
The factors that effect the germination of seeds are: · Temperature · Acid rain · Oxygen · Water I will just see what effect does the acid rain have on germination of seeds.
Short-Term Effect of Temperature Changes on the Rate …
Leaf temperatures generally follow the diurnal changes in air temperatures (Fig. 14.4). At sunrise with a clear sky there is a rapid rise in air temperature and leaf temperature, with a slower and lower rise in root and surface soil temperature. This relationship is altered considerably by cloud cover and at night root temperatures will be higher than leaf temperatures. Organ volume (thickness) can also have a marked influence on temperature and this can be seen, for example, in the apple-growing regions around Auckland in New Zealand. On a windless sunny day with an air temperature of 26°C, while leaf temperature in an apple orchard may reach 29°C, the peripheral flesh of the fruit on the sunny side of a tree can reach 45°C.
The Effect of PH on the Rate of Photosynthesis | …
For annual crops some degree of adjustment is possible to avoid a particular environmental stress by varying the cultivar or time of planting. However, even this increased flexibility may not be adequate to cope with the irregular nature of many stresses. In the wheat-growing areas of Australia, temperatures increase from the time of heading through to crop maturity so that grain ﬁlling often occurs at above-optimum temperatures. Added to this is the possibility of extreme high temperatures (heat shock) or drought. In warmer growing regions these temperature extremes may be avoided in part by earlier planting, but this approach will depend on suitable temperature conditions and the availability of water for germination and seedling establishment early in the year. In cooler wheat-growing regions earlier planting may expose the developing infloresence to possible frost damage resulting in reduced fertility and grain set (Figure 14.3).