深圳市西海岸和海域生物资源多样性的管护

本文着重介绍生物多样性管护区的基本含义和要求,结合深圳市西海岸和海域的特点,提出建立珠江口南海海岸和海洋生物多样性管护区,以发挥该区域的资源优势和持续利用,为建设深圳特区做出应有的贡献。     

Dynamic sweating response of man to infrared irradiation in various spectral regions

In an attempt to detect differences in the thermal effect of infrared irradiation of different wavelengths, transient sweating response to infrared irradiation in various spectral regions was examined. In Series 1, the ventral or dorsal surface of the nude subject was irradiated repetitively for a period of 4 min (2 min on, 2 min off) by each of three kinds of infrared heaters with main emissivity in near-infrared (NIR; 0.7–2.8 m), intermediate-infrared (MIR; 1.5–5.8 m), and far-infrared (FIR; 2.8–25 m) regions. The sweating response on a non-irradiated area tended to be the greatest with MIR, while the magnitude of the sweating response on the irradiated area showed no consistent differences among various wavelengths. The results infer that MIR stimulated cutaneous thomoreceptors most effectively, while its direct effect on local sweat gland activity was minimal. In Series 2, the effects of 9–12 min irradiations in more restricted ranges of wavelength were compared by the combination of the three kinds of heaters with filters (translucent to wavelength ranges of 1.3–2.7, 2.7–3.5, 3.6–8.0 m, respectively). The sweating response on a remote area was predominantly greater with the range of 2.7–3.5 m than with the other wavelength ranges, while the local effect on sweating was minimal with this range. The results of Series 2 reinforce those of Series 1, indicating that the degree of stimulation of cutaneous thermoreceptors and of direct thermal effect on sweat gland activity differ with spectral regions incident on the skin, thus affecting local and remote effects on the sweating response.     

黄土丘陵半干旱区不同作物生态效能研究

深入研究特定生态环境条件下不同作物生产力及其生态效能,对于合理调控农田生态系统,探讨提高系统生产力途径具有重要意义。60年代以来,在国际生物学计划(IBP)的影响下,美国、日本、菲葎宾等国先后进行了小麦、水稻、大豆等作物农田生态效能研究。我国于“六·五”期间分别在南方稻区、黄淮海平原以及北方灌区等不同农业区开展了多种作物种植制度生产力问题研究,并取得重     

Influence of grazing and soil conditions on secondary savanna vegetation in India

Abstract. Savanna vegetation and pertinent soil features were studied on 43 sites in a dry tropical forest region of India. Grazing intensity ranged from 0.68 to 0.98. Soil moisture was positively related to the proportion of fine soil particles (< 0.1 mm), and the latter decreased while the proportion of coarse particles (2.0-0.5 mm) increased with increasing grazing intensity. Canopy biomass ranged from 28 to 104 g/m² in grazed communities and from 230 to 337 g /m² in ungrazed communities and was positively related to vegetation cover which ranged between 30–72 % in grazed and 68 - 91 % in ungrazed communities. Vegetation cover was negatively related to grazing intensity. Species richness and diversity were highest at low grazing intensity. Using community coefficients and Detrended Correspondence Analysis, the grazed stands were clustered into six and the ungrazed ones into three communities. The grazed communities were recognised as degradation stages and the ungrazed ones as recovery stages. Only five grass species, in various combinations were able to dominate in one of the different stages. Evidently the harsh climatic conditions (high temperatures, high variability in rainfall and a long dry period) in the region permit only a few species already adapted to these conditions to participate in the succession.     

Water utilization of tropical hardwood hammocks of the Lower Florida Keys

Summary Predawn water potential of representative plant species, together with stable isotope composition of stem water and potential water sources were investigated in four low-elevation tropical hardwood hammocks in the Lower Florida Keys, during a one year period. Hammock species had the lowest water potentials when soil water content was low and/or soil salinity was high, but differences in groundwater salinity had no effect on the water potential. Comparison of D/H ratio of plant stem water with soil and ground water corroborates the conclusion that they are primarily utilizing soil water and not groundwater. Thus, tropical hardwood hammocks are buffered from saline groundwater, and are able to thrive in areas where groundwater salinity is as high as 25. The effect of sea level rise on these forests may depend more on changes in the frequency of tidal inundation of the soil surface than on changes in groundwater salinity.     

A simple method for shortening a plasmid genome using a system of plasmid cointegration mediated by a Tn3 mutant

This paper describes a simple method for the isolation of small plasmids of various sizes from pSMI, a derivative of the resistance plasmid R 100. The method is based on the observation that a repressor-negative mutant of the ampicillin-resistance (amp^r) transposon Tn3, Tn3 No. 5, mediates cointegration of a plasmid carrying Tn 3 No. 5 (pMB8::Tn 3 No. 5) into virtually any site on pSMI. The resulting cointegrate plasmids contain the pSMI sequence which is joined with the amp^r gene of the Tn 3 mutant. This cointegration is so frequent that large cointegrate plasmids can be readily detected in the total plasmid DNA prepared from cells carrying pSMI and pMB8::Tn3 No. 5. We were able to isolate small plasmids of various sizes by digesting the total plasmid DNAs with restriction endonucleases which cut both pSM 1 and Tn3 No. 5 sequences present in the cointegrates and subsequently ligating the restriction fragment containing both the amp^r gene and the region necessary for replication of pSMI. Analysis of these plasmids, named pBV plasmids, with restriction endonucleases and by nucleotide sequencing allowed us to determine regions necessary or unnecessary for replication, thus defining a minimal replication region of pSMI. The present method is generally useful for the isolation of small derivatives from any large plasmid for the study of genes and sites adjacent to or within the minimal replication region of the plasmid.