Herbivorous insect species in the tree canopy of a relict South African forest

Abstract.

• 1 The herbivorous insects on twelve species of evergreen broadleafed trees were repeatedly sampled over a period of 11 months in a small relict forest on the east coast of South Africa. This extraordinarily speciose forest patch has an unusually high proportion of endemic tree species, some of which are extremely rare.
• 2 The insect herbivore fauna (number of species) seems to be markedly depauperate compared to that reported on native, broadleafed trees from other parts of the world. Some possible reasons for this are discussed.
• 3 The total number of herbivorous insect species on each tree species was strongly correlated with the local relative abundance of the host plant species.
• 4 There was no relationship between the total number of insect herbivore species on each tree species and the relative taxonomic isolation of the trees. The proportion of seemingly unique (= specialist) herbivorous insect species (i.e. those that occurred on one tree species only) was greatest on taxonomically isolated trees.
• 5 A fundamental deficiency in the interpretation of the data in this study, and of many other similar studies that report on the number of insect species on plants, is discussed, namely the lack of clarity on the closeness of the association between individual insect herbivore species and their respective host plants.

     

离体条件下诱导番茄果实状结构的再生

以番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．）雌蕊和幼果的组织作外植体可以诱导果实状结构的再生。这种果实状结构在离体条件下能培养成熟,成熟时具红色。解剖观察表明：果实状结构由果肉和包围在外面的果皮组成,无种子和胎座。外源激素和外植体年龄的试验揭示：１．以雌蕊组织作外植体时,仅附加外源细胞分裂素就可以诱导果实状结构的再生,外源生长素似乎不是必需的,最高的诱导频率（５０．０％ ）出现在仅附加玉米素０．５ ｍ ｇ／Ｌ的组合。２．从直径４—１２ ｍ ｍ 的幼果上分离的外植体在附加外源激素的培养基上均可诱导果实状结构的再生,但只有从直径８ ｍ ｍ 的果实分离的组织块作外植体并将它们培养在６－ＢＡＰ ２ ｍ ｇ／Ｌ,ＮＡＡ０．１ ｍ ｇ／Ｌ的培养基上时,果实状结构的诱导频率最高（６２．５％ ）。为了探讨在果实状结构再生中表现出来的细胞全能性的表达,提出了植物细胞全能性的部分表达（Ｐａｒｔｉａｌｅｘｐｒｅｓｓｉｏｎ ｏｆｐｌａｎｔ ｃｅｌｌｔｏｔｉｐｏｔｅｎｃｙ）的概念并进行了讨论。     

田林老山中山两类森林凋落物研究

田林老山中山两类森林凋落物研究梁宏温（广西农学院林学分院,南宁５３０００１）ＳｔｕｄｉｅｓｏｎｔｈｅＬｉｔｔｅｒｆａｌｌｏｆＴｗｏＦｏｒｅｓｔＴｙｐｃｓｉｎＭｉｄ—ＡｌｔｉｔｕｄｅｏｆＬａｏｓｈａｎＭｏｕｎｔａｉｎｉｎＴｉａｎｌｉｎＣｏｕｎｔｙ．￥Ｌ...     

Use of lysophosphatidylethanolamine, a natural lipid, to retard tomato leaf and fruit senescence

We studied the influence of lysophosphatidylethanolamine (LPE) on the pattern and rate of ethylene production and respiration of tomato ( Lycopersicon esculentum cv. H7155) leaflets and fruit. Leaflets that had been senescing on the plant showed a climacteric-like rise in ethylene production but not in respiration rate which decreased continuously with leaf age. Detached leaflets had a climacteric-like pattern in respiration whether they were incubated in complete darkness or in light. Detached leaflets incubated in the dark had higher rates of ethylene production and CO₂ evolution than did light-incubated leaves. There was no change in the pattern of ethylene production or CO₂ evolution as a result of LPE treatment. However, LPE-treated attached and detached leaflets had consistently lower rates of CO₂ evolution. The reduction in CO₂ evolution by LPE was most pronounced at the climacteric-like peak of the detached leaves. LPE-treated leaflets had a higher chlorophyll content and fresh weight and lower electrolyte leakage than the control. LPE-treated fruits had lower rates of ethylene and CO₂ production than did the control. LPE-treated fruits also had higher pericarp firmness and lower electrolyte leakage than the control. The results of the present study provide evidence that LPE is able to retard senescence of attached leaves and detached leaves and tomato fruits. Several recent studies suggest that lysolipids can act in a specific manner as metabolic regulators. Our results suggest a specific role of lysolipid LPE in aging and senescence     

Internal carbon dioxide and ethylene levels in ripening tomato fruit attached to or detached from the plant

The carbon dioxide and ethylene concentrations in tomato fruit ( Lycopersicon esculentum cv. Castelmart) and their stage of ripeness (characteristic external color changes) were periodically measured in fruit attached to and detached from the plant. An external collection apparatus was attached to the surface of individual tomato fruit to permit non-destructive sampling of internal gases. The concentration of carbon dioxide and ethylene in the collection apparatus reached 95% of the concentration in the fruit after 8 h. Gas samples were collected every 24 h. A characteristic climacteric surge in carbon dioxide (2-fold) and ethylene (10-fold) concentration occurred coincident with ripening of detached tomato fruit. Fruit attached to the plant exhibited a climacteric rise in ethylene (20-fold) concentration during ripening, but only a linear increase in carbon dioxide concentration. The carbon dioxide concentration increases in attached fruit during ripening, but the increase is a continuation of the linear increase seen in both attached and detached fruit before ripening and does not exhibit the characteristic pattern normally associated with ripening climacteric fruit. In tomato fruit, it appears that a respiratory climacteric per se, which has been considered intrinsic to the ripening of certain fruit, may not be necessary for the ripening of "climacteric" fruit at all, but instead may be an artifact of using harvested fruit.     

Accumulation of calcium, potassium and magnesium in apple fruits under various conditions of humidity

In each of two experiments done under controlled conditions, starting at bloom, 4 humidity treatments were applied to potted trees of apple ( Malus pumila Mill. cv. Cox's Orange Pippin), i. e. in experiment 1: (1) high humidity throughout, (2) low humidity throughout, (3) low humidity for 7 weeks followed by high humidity for 6-7 weeks, and (4) the reverse (first high and then low humidity); in experiment 2: (1) day/night humidity high/high, (2) low/low, (3) low/high, and (4) high/low.
In both experiments high humidity favoured shoot growth appreciably. Change from low to high humidity after 7 weeks resulted in some growth stimulation but in the reverse situation growth was markedly reduced. Shoot growth responded little to different night humidities. In the two experiments fruit growth was little affected by treatments. In experiment 2 irrespective of night humidity, water consumption was higher at low than at high day humidity. In the high/low humidity regime water use during the night was high and leaf water potential low, relatively; during the day water potential was little affected by treatments.
At any time leaf Ca and Mg were clearly highest at low day humidity; night humidity had no effect. Leaf K did not respond to treatments. Fruit Ca at high humidity throughout was lower than at low humidity throughout. Increasing humidity later in the season was ineffective but a decrease at that time tended to reduce fruit Ca slightly. The clearly lowest Ca values occurred in the high/low day/night treatment. Fruit K and Mg were not or hardly affected by treatments.
The findings are discussed in terms of humidity effects on transpiration, shoot and fruit growth, and xylem mineral concentration and ion exchange translocation along the xylem walls.     

Biomass and carbon storage of the North American deciduous forest

Field measures of tree and shrub dimensions were used with established biomass equations in a stratified, two-stage cluster sampling design to estimate above-ground ovendry woody biomass and carbon storage of the eastern deciduous forest of North America. Biomass averaged 8.1 ± 1.4 (95% C.I.) kg/m² and totaled 18.1 ± 3.1 (95% C.I.) gigatons. Carbon storage averaged 3.6 ± 0.6 (95% C.I.) kg/m² and totaled 8.1 ± 1.4 (95% C.I.) gigatons. These values are lower than previous estimates commonly used in the analysis of the global carbon budget which range from 17.1 to 23.1 kg/m² for biomass and 7.7 to 10.4 kg/m² for carbon storage. These new estimates for the deciduous forest, together with earlier work in the boreal forest begin to reveal a pattern of overestimation of global carbon storage by vegetation in analyses of the global carbon budget. We discuss reasons for the differences between the new and earlier estimates, as well as implications for our understanding of the global carbon cycle.     

Factors affecting in vitro clonal propagation of Prosopis cineraria

Genotype, age of tree, nature of explant and size (length and diameter), season of explant collection, explant position on medium, plant growth regulators and certain additives (ascorbic and citric acids, adenine sulphate, L-arginine, glutamine and ammonium citrate), incubation conditions, and subculturing period greatly influenced the in vitro clonal propagation of P. cineraria. The maximum number of 10–12 shoots were induced from the nodal shoot segment from pruned thorny adult trees on Murashige and Skoog's (MS) medium containing 0.1 mgl^-1 indole- 3-acetic acid (IAA)+2.5 mgl^-1 benzylaminopurine (BAP)+additives. Higher temperature (31+-2°C) and mixed (fluorescent and incandescent) light of 50 mol m^-2 s^-1 photon flux density for 12 h per day photoperiod favoured shoot induction and subsequent growth. Explants from thornless trees produced 6–8 shoots per explant on MS medium containing 0.1 mgl^-1 IAA+5.0 mgl^-1 BAP + additives. Nodal shoot segments obtained from root and stump sprouts produced multiple shoots. Root segments differentiated into multiple shoots on MS medium containing 0.5 mgl^-1 indolebutyric acid (IBA)+2.5 mgl^-1 BAP.Differentiated shoots multiplied best on MS medium containing 0.1 mgl^-1 naphthalene acetic acid (NAA)+1.0 mgl^-1 BAP + additives. To yield multiple shoots the original explant was transferred 6 times on fresh medium after harvesting the differentiated shoots. Shoots were rooted by pulsing with 100 mgl^-1 IBA for 4 h and then culturing on hormone-free half strength MS medium. Initial dark incubation for 5 days at high temperature (33±2°C) was found essential for root induction from shoots which was 63% within two weeks. The rooted plantlets contained a consistent number of chromosomes (2n=28). It is suggested that the protocol developed could be useful for cloning of mature and tested trees of P. cineraria.     

Fruit developmental regulation of the kiwifruit actinidin promoter is conserved in transgenic petunia plants

We have examined the expression of actinidin, a cysteine protease found in kiwifruit, over the course of fruit development. Protease activity was first seen in fruit that had reached about half their final weight, and rose to high levels at harvest. The 5-flanking region (nucleotides –1301 to +58) of a kiwifruit actinidin gene was fused to the -glucuronidase (GUS)-coding region, and the chimaeric gene was introduced into transgenic petunia plants. Induction of the GUS gene was observed during the later stages of seed pod development, closely resembling the pattern of actinidin induction in fruit tissues of kiwifruit. Some GUS expression was also detected in the vascular system of the receptacle, leaves, stems and roots. A shorter promoter fragment consisting of nucleotides –115 to +58 conferred similar spatial and temporal regulation in some of the transgenic plants.