Secondary Needles Research Articles

Four species of Lophodermium on Pinus sylvestris

Four species of Lophodermium Chev. are distinguished on secondary needles of Pinus sylvestris L. by the manner in which their ascocarps are embedded in the host and their ability to produce stromatic lines of different sorts across the needle. The four species, L. pinastri (Schrad. ex Hook.) Chev., L. conigenum Hilitzer, L. pini-excelsae Ahmad and L. seditiosum sp.nov. are keyed out, described and figured.

Seasonal Effects on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris

AbstractChloroplasts were isolated from primary needles of 1‐year‐old seedlings and from secondary needles of a 20‐year‐old pine tree in a natural stand. In autumn the electron transport capacities of PSII, PSI and PS (II + I) decreased and the electron transport between PSII and PSI became inhibited in October in the 20‐year‐old tree. This inhibition lasted until May the following year. The partial reactions of PSI and PSII still showed low but fairly constant rates during the whole winter seedlings. Seasonal changes in the electron transport properties of 1‐year‐old showed the same general trends as observed in the 20‐year‐old tree, but the changes were less pronounced. However, in snow‐covered seedlings the PSI‐mediated electron transport and the electron transport from H2O to NADP increased during the late winter when the seedlings were still covered by snow. The total chlorophyll content of the needles decreased in autumn and winter. Low temperature fluorescence ratios of F692/F680 and F726/F680 indicated more severe destruction of the chlorophyll a antennae closely associated with the two photosystems than of the light harvesting chlorophyll a/b complex. In this case, too, the changes were more pronounced in the 20‐year‐old tree than in the 1‐year‐old seedlings. The chlorophyll/P700 ratios indicated a more marked reduction in the reaction centre molecules during autumn than in the antennae chlorophyll molecules. The changes in electron transport and low temperature fluorescence properties which occurred during autumn and winter were mainly reversed during spring.

Effects of Frost Hardening and Dehardening on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris

AbstractPhotosynthetic electron transport and low‐temperature fluorescence emission properties have been analyzed in isolated chloroplasts during the course of frost hardening and dehardening of Pinus silvestris L. Both the partial electron‐transport reactions (H2O DPIP and Asc./DPIP NADP) and the overall electron transport (H2O — NAPD) showed decreasing capacities during the course of hardening. Upon exposing the plants to −5°C and high irradiance a block in the electron‐transport chain between the two photosystems developed, whereas the partial reactions still showed activities. The decrease in activity of PSl was accompanied by a decrease in P700 content, as determined by light oxidation of P700, which indicates a correlation between the two changes.Hardening also induced changes in the in vivo chlorophyll organization. During the course of hardening the fluorescence emission bands F692 and F726 decreased relative to F680. These changes were more pronounced if the plants were treated in high than in low irradiance. This suggests a greater destruction of the chlorophyll antennae in close association with the two photoreactions than in the so‐called light‐harvesting chlorophyll a/b antenna.During dehardening basically the reverse of the changes observed during hardening occurred. The recovery of secondary needles was complete, whereas primary needles only partly recovered.

Histological Changes Induced in Scotch Pine Needles by Sulfur Dioxide

Scotch pine cotyledons, primary needles, and secondary needles of various ages were exposed to 2620 ..mu..g/m/sup 3/ (1.0 ppm) SO/sub 2/ for 1, 3, or 5 hr. Needles from unexposed (control) and exposed plants were embedded in paraffin, sectioned, stained, and examined under a light microscope. Mesophyll collapse was the most common structural change induced by SO/sub 2/ in all three needle types. Resin canal occlusion also was observed in primary and secondary needles exposed to SO/sub 2/. Increased dosages of SO/sub 2/ did not induce additional symptoms but intensified those already present.

White pine blister rust: hypersensitive resistance in sugar pine

Resistance to white pine blister rust in sugar pine is simply inherited and can be identified by distinct needle spot morphs. After artificial inoculation at 2 years of age, seedlings from selfed and full-sib families developed either 'fleck' spots, characterized by a pale, yellow margin with a necrotic fleck in the center, or they developed typical yellow or red spots (or both). Seedlings segregated for needle spot reaction in monohybrid ratios with fleck dominant. Mycelium in secondary needle tissues of fleck spots, in contrast to yellow and red spots, was relatively sparse and confined by dense tannin deposits. Bark infection and mortality was heavy on seedlings with yellow and red spots. On seedlings with fleck spots, no bark symptoms developed from secondary needle infection but small, abortive cankers did develop on some of these seedlings as a result of primary needle infection. These atypical cankers did not sporulate or spread extensively, and had healed by the 2nd year after inoculation. The gene responsible for the fleck reaction thus elicits a hypersensitive response in secondary needles and, apparently, in bark tissues as well.

The influence of nitrogen nutrition on the dynamics of growth and metabolism of endogenous growth regulators in Scotch pine (Pinus silvestris L.) seedlings

Pine seedlings were cultivated in sterile agar cultures containing nitrogen as NH4Cl. The most pronounced positive effect on the growth of seedlings was affected by N used at a concentration of 50 ppm. After 4 months was stated that nitrogen had only a slight effect on elongation, of .shoots but decreased the length of roots. Nitrogen increased the lenght and number of primary and secondary needles as well as the fresh and dry matter of sboots. It stimulated also the number of lateral roots and the fresh and dry matter of the root system. Stimulation of shoot growth and differentiation as a result of nitrogen treatment was correlated with the increase -of free gibberellins and auxins and decrease of the amount of bound gibberellins and ABA-like inhibitor in shoots. However the effect of N on growth of roots was connected with the increase of auxins, cytokinins and ABA-like inhibitor in these organs.

The Influence of Plant Age on the Sensitivity of Virginia Pine to Ozone

Virginia pine seedlings in the cotyledon, primary needle, and secondary needle stages were injured after exposure to 25 pphm O/sub 3/ for 2 hr. All three needle types reached maximum sensitivity to O/sub 3/ at approximately 3-5 weeks following initiation of needle growth, after which time the sensitivity declined. Cotyledons became resistant at 16 weeks; primary needles were still sensitive at the oldest age studied; secondary needles became resistant at 18 weeks. The basal portions of the cotyledons were more sensitive than the tip or mid portions. The youngest primary and secondary needles were injured most severely at the needle tip, whereas older needles were more severely injured at the base. The three needle types showed similar symptoms, mainly chlorotic mottle and tissue necrosis, as well as similar dosage-response curves. Dormant 3-year-old plants exposed to O/sub 3/ in December were highly resistant.

Effect of Temperature and Light Intensity Early in Ontogeny on Growth of Pinusresinosa Seedlings

Low temperature or low light intensity following germination of Pinusresinosa seeds greatly suppressed subsequent seedling development, with cotyledon expansion inhibited more than root expansion. A strong influence of shoot environment early in ontogeny was demonstrated on initiation of all but a few early-formed primary needle primordia and on expansion of all primary needles, including those formed early. Low temperatures or low light intensities during the cotyledon stage of development prevented initiation of most of the normal complement of primary needles. However, when seedlings were placed in a favorable environment following prolonged exposure to low temperature or low light intensity, primordia of primary needles formed readily and subsequently expanded. Following seed germination, the young seedling is a system of competing carbohydrate sinks. Early development of the seedling is an integrated continuum with the source of growth requirements shifting during ontogeny, from megagametophytes to cotyledons, to primary needles, to secondary needles. The importance of cotyledons and primary needles to early seedling development is emphasized.