Jan Pilarski

Gradient of photosynthetic pigments in the bark and leaves of lilac [Syringa vulgaris L.]

The concentration of chlorophyll and a carotenoids in the bark of stems of different age and in the leaves of lilac (Syringa vulgaris L.) was determined.The thickness of bark changes with the age of the stems, ranging from 0.73 mm in the current-year stems to 1.22 mm in 3-year-old ones. Chlorophyll and carotenoids were present through the whole thickness of the bark, except the cork. It was found that chlorophyll and carotenoids are located mainly in the outer layer of the bark, immediately under the cork, to a depth of 400 µm. In this layer the chlorophyll a/b ratio is the highest and the content of chlorophyll is four times larger than that of carotenoids. When penetrating deeper into the bark, the content of chlorophyll and carotenoids as well as the chlorophyll a/b ratio diminishes.Investigations of the leaves showed that most of the chlorophyll is found in the palisade parenchyma, the chlorophyll a/b ratio is the highest in the upper layer.The highest concentration of chlorophyll in the bark is 0.44 mg·dm−2 and in leaves −1.2 mg−2·dm−2. The highest value of the chlorophyll a/b ratio in the bark is 3.8, and the lowest 0.5, while in the leaves it varies from 4.5 to 3.8 Low values of the chlorophyll a/b ratio are due to the shade conditions existing in the bark and they are evidence of very great differentiation of light conditions within it.

Optical properties and the content of photosynthetic pigments in the stems and leaves of the apple-tree

Optical properties and changes in the content of photosynthetic pigments (chlorophyll and total carotenoids) were investigated in the bark and leaves of the apple-tree during a year.Optical properties of stems change with their age. Light reflectance of current year stems equalled 14.2%, while the one for 3-year-old stems decreased to 10.2%, absorption for the current year stems equalled 55.5% and increased up to 66.4% for 3-year-old ones. Light transmittance for the cork of current year stems equalled 30.2%, and decreased with the age of stems reaching 23.4% for the 3-year-old ones. The cork transmitted less than 5% of light of 400 nm, but the transmittance increased with the increase in the wavelength up to 55% at 700 nm. The reflectance of light by the leaf equalled 6.9%, absorption 89.7%, and transmittance 3.4%.In August the highest amount of chlorophyll pigments (6.2 mg·dm−2) and carotenoids (1.63 mg·dm−2) was detected in the leaves of the apple-tree, however, the ratio of chl a/b reached the highest value 4.12 in June.For the bark of apple-tree stems the content of chlorophyll pigments increased since spring and reached the maximum content of about 2.8 mg(chl)·dm−2 for 1-3-year-old stems in the summer months, while for the current year stems in October. The ratio chl a/b was at the same level, about 2.2 during the whole year. The content of carotenoids was lower in stems than in leaves and was at the similar level during the year, however, it increased with the age of stems.Minor changes in the optical properties and the content of photosynthetic pigments occurring with the age of stems may be due to the low increment in cork thickness in the studied age groups of plants.

Chlorophyll distribution in the stems and trunk of beech trees

The distribution of chlorophyll was examined in cross-sections of 2- and 6-year-old stems as well as in the bark of the stump trunk of beech trees, utilising chlorophyll autofluorescence. The investigations were conducted using a confocal microscope. The tests carried out on 2 – 6-year old stems showed a large presence of chlorophyll in the bark, in primary and secondary rays as well as in the pith, but smaller amounts in wood parenchyma cells. There was no chlorophyll in the cork, sclerenchyma: in wood in vessels, tracheids and fibers. A reduction in the chlorophyll content in 6-year-old stems was not observed. In the bark of the trunk, chlorophyll was found in large amounts directly under the cork and in vestigial amounts in the primary phloem.

Diurnal and seasonal changes in the intensity of photosynthesis in stems of lilac [Syringa vulgaris L.]

It has been demonstrated that during the whole year the stems are photosyntheticaly active and capable of assimilating atmospheric CO2. The intensity of photosynthesis varies. During the vegetation period the registered net photosynthesis lasted up to 13 hours per day, and in the leafless period for 2–3 hours a day. Photosynthesis was registered also at temperatures below zero (−3 °C) as a reduced CO2 evolution in light in comparison with darkness. The maximal net photosynthesis values during the vegetation period amounted to 6 up 8 µmol (CO2)·m−2·s−1, and in the leafless period 0.5 – 1 µmol (CO2)·m−2·s−1, and they were close to being up to twice as big as the values obtained of darkness respiration. An increase of the photosynthetic activity of stems preceded the spring development of the leaves.

The content of photosynthetic pigments and the light conditions in the fruits and leaves of sweet pepper

Investigations were carried out on the fruits of sweet pepper at its two development stages: on green fruits, on mature red and yellow fruits and on leaves. The content of the photosynthetic pigments and the optical properties were examined.In the green fruits when compared with leaves the content of the photosynthetic pigments is smaller by 40 to 50 % and the value of the ratio: chlorophyll a/b is lower. Chlorophyll is absent in mature fruits, while the content of carotenoids is a few times higher.The optical properties of green fruits and of the leaves in the PAR (photosynthetically active radiation) range are the same. In the range 700–1100 nm the green fruits show smaller reflectance and transmittance and a few times greater absorptance of irradiation which contributes to the warming up of the seed bag, while small absorptance of leaves in this range protects them against overheating.In mature fruits, in the PAR range, the reflectance and transmittance are higher, while the absorptance of irradiation in comparison with that of green fruits is smaller. In the range 700 – 1100 nm the changes are rather small and refer to the increase of reflectance and reduction of absorptance, while the transmittance of irradiation remains unchanged.

Effect of drought stress on leaf optical properties in drought-resistant and drought-sensitive maize and triticale genotypes.

The effect of a short (7 d), prolonged (14 d) soil drought (D) and (7 d) recovery (DR) on the leaf optical properties — reflectance (R), transmittance (T) and absorptance (A) in photosynthetically active radiation (PAR) and near infrared radiation (NIR) range of irradiation (750–1100 nm) was studied for maize and triticale genotypes differing in drought tolerance. The drought stress caused the changes in leaf optical properties parameters in comparison with non-drought plants. The observed harmful influence of drought was more visible for maize than triticale.

Measurement of light gradient in plant organs with a fiber optic microprobe

A light fiber optic system for the measurement of the radiation transmittance gradient in the plants organs is described. The radiation of halogen lamp is carried by a light fiber cable, 2 mm thick, into the examined material. Radiation passing through the plant material is mainly absorbed, and partly transmitted to the inner layers of the cells.Radiation transmitted by the plant material falls on the receiving light fiber, 50 m thick, and is carried onto the radiometer. The receiving light fiber, placed in the injection needle, is introduced into the examined material, which enables the measurement of radiation gradient transmittance in the examined material.An example of the utilisation of the measurement system are the results obtained on the leaves and bark of the current-year stems of lilac and on bean pods. The obtained results are in agreement with the distribution of photosynthetic pigments in these organs.